Hydronic baseboard system nightmare

Cherny

Hello,
I have been reading and learning from this forum for the past 6 months after we bought a house with a boiler/hydronic baseboard system that was not working to its full potential. We are at a point where we are considering re-piping the whole system this summer and starting fresh, but I'd like to at least try to fix the system now and see if we can get it working to a reasonable level for the remainder of this winter.

Background: The system is a 6 zone hydronic baseboard system running off a Weil-Mclain CGA-4 boiler. All 6 loops consist of 3/4" polybutylene pipe running through the slab with 3/4in copper fin tube baseboards. The zones operate on 6 Honeywell valves controlled by independent thermostats around the house. Circulator is a Grundfos 15-58.
The house itself is wood frame construction from 1986, located in British Columbia. 2x6 walls. R20 ceilings. Double pane aluminum windows. Moderately drafty (another project in progress).
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Boiler is set to 180F. Pressure gauge read 15psi cold, 20psi @ 180F.
"Efficiency" setting is set to Minimum.
No error codes/lights on boiler which is only a few years old.

Longest run is suspected to be about 150ft of 3/4 polyb/copper.

We are aware the boiler is marginally sized for the size of this house and we will likely require a secondary heat source. We are thinking of putting in a gas fireplace in our main living area to supplement some BTUs, but we would like to assess this once the hydronic system is working adequately.
We are also doing some building envelope improvements to reduce drafts... spray foam any gaps, caulking windows, and will likely be adding another R20 in our attic in the next few weeks (bringing us up to R40).

System diagram:



Situation: system is unable to heat the house to a comfortable level (our living room is barely able to maintain 64F with outside temperatures hovering around freezing and thermostat set to 70F -- and only by sacrificing heat on the other side of the house). We are unable to get heat in all zones at the same time. This is the main list of "problems"
- Zone 6 is not getting any water flow and we are unable to flush it. This zone has essentially been abandoned as it only services one room in the basement. We are heating it with a small electric heater.
- We are only able to get heat in one, sometimes 2 zones at a time. All zones, except for Zone 6, can get heat if all the other ones are shut off/not calling for heat. If more than one zone calls for heat, radiators go from hot to warm or cold. Based on the diagram I drew, we are unable to get heat in Zone 1 or 2 AND any of the other zones at the same time (more on this below).

Diagnostics and repairs already done:
-we had a plumber (recommended by the previous home owner) come when we first moved in a few months ago and together we flushed all the zones with the pressure reducing valve flipped up, both backwards and forwards. That was the extent of his suggestions on diagnostics. He did not strike me as being very knowledgeable on these systems. We have flushed all zones 3 times now, for extended periods of time. Lots of brown sludge and sediment came out the first time, less so the second and third time. For Zone 6 we can only get a slight trickle of water flowing through both forwards and backwards.
- Every baseboard has an air vent fitting. They have all been opened after flushing. No air found. System is very quiet when running. The air vent in the zone 6 baseboard leaks a very slight trickle of water when opened, and I can see "crud" in the line under the fitting. The zone is either plugged or the line may have kinked in the slab when the house settled?
- Thermostats are all new and the correct type (24V)
- I have verified the mechanical heads on all the zone valves work correctly. They all open when the thermostats are calling for heat and shut off also.
- I opened the actual valve for Zone 6 and verified it is not plugged and internals work as they should.
- While playing with zones in an attempt to figure out where the problem was, I noticed the longer zones servicing the upstairs take a long time to warm up when calling for heat. The Grundfos circulator is set on Speed 3 so this seemed odd as there should be a fair bit of flow through the 3/4inch pipe with only one zone opened. The head loss in the system SHOULD be fairly low given the longest loops are estimated to be around 150ft and they are 3/4inch all the way through. I checked the amperage on the circulator while running and it consistently draws around 0.6amps while running, which is quite a bit below what the plate says should draw for speed 3 (should be closer to 0.75amps). At this point, I suspected possibly a bad circulator and decided to swap it out. I bought a new 15-58 and swapped it in, but unfortunately system performance did not change. New pump also only draws about 0.6amps. Pump was primed and system was flushed free of air again.
- While swapping the pump though I noticed A LOT of crud in the elbow directly below the pump between the pump and the boiler (see picture).
- There are no visible leaks anywhere in the boiler room.
- Expansion tank has 12psi in the chamber (matching the pressure reducing valve). Tank has a noticeable change in sound in the top vs bottom half.
- All the baseboards are installed correctly with a good sized gap underneath of about 1.5inches. They have all been vacuumed and brushed clean. The fins are in good shape and oriented correctly.

Problems to be addressed and theories:
- The return lines for zone 1 and zone 2 go into a T, with zones 3/4/5/6 coming in on the opposite run, all feeding into the branch of the tee that goes to the circulator. This seems like a bad idea to have zones competing for flow into the T from opposite sides. I plan on simply moving the returns from zone 1 and 2 so all zone returns are flowing in the same direction.
- I also suspect there is something obstructing flow in the system, likely near the boiler as it seems to affect all zones. Maybe some of this crud has formed a plug somewhere which is throttling the circulator pump (leading to poor flow and low amp draw on the circulator)? I am not sure how to deal with this given that flushing the system has not removed it. While flushing the system I have let some water (at lower pressure) run through the boiler (in case that's where the sediment is) to try and flush that section of the system too, but it obviously did not work as I found all that crud when I changed the circulator.
- Should I keep flushing the system? Could it be just a crud plug somewhere near the boiler that's throttling the pump output and thus there is only enough flow to sustain one zone at a time? Plus with the returns opposing each other, they are competing for the T on the return?

Does anybody have any other ideas of things I could try?
Like I said above, we are considering re-piping the system this spring/summer as we would like to get rid of the polybutylene pipe but we may delay it another year or two if we can get the system working to an acceptable level.

Sorry for the long post and thank you for any ideas!!

hot_rod

The sludge is a result of the polybut tube used. At high temperatures it allows quite a bit of O2, which corrodes and rusts all ferrous components. I'm not sure up there, but in the U.S. PB needs to be disclosed on the real estate transaction. At least on the plumbing side.

That sludge coats the inside of the boiler and all the piping and fin tube reducing heat transfer. In some cases it will plug the tube completely, like concrete That may have happened in some zones? Disassemble the Spirovent, they tend to plug badly with that sludge. Same with any other strainers anywhere.

A power flush with a pump cart may salvage some and increase output.
Sludge formation will be an ongoing issue.

Add a cleaner, run for days then flush with a high flow rate pump. In some cases this needs to be done multiple times. I've seen barrels of sludge flushed from non barrier tube systems. Flushing with 12- 20 psi fill water will not be adequate.

While you try this, do a room by room heat load. Possibly there is inadequate fin tube to heat some rooms?

HomerJSmith

Polybutylene pipe, ain't that the Shell Oil crap? In domestic plumbing that stuff disintegrated, so I can imagine what happens in a hot water boiler sys. I believe there was gray piping that InFloor put out that wasn't Polybutylene. Shell had a class action suit against it for that pipe.
That sys needs a though cleaning and a power flush for starters. Sometimes I have had to flush a sys 4 times with cleaner each time before the water was acceptable.

mattmia2

Does the boiler stay at 180 when the zones get cold? If it does then it is the flow problem from the sludge @hot_rod mentioned. You could set it up with a heat exchanger and nonferrous components on the plastic tube side but you're probably investing a lot in to borrowed time on the tubing.

Maybe try keeping it filled with inhibitor once you get things cleaned out.

Cherny

hot_rod said:

The sludge is a result of the polybut tube used. At high temperatures it allows quite a bit of O2, which corrodes and rusts all ferrous components. I'm not sure up there, but in the U.S. PB needs to be disclosed on the real estate transaction. At least on the plumbing side.

That sludge coats the inside of the boiler and all the piping and fin tube reducing heat transfer. In some cases it will plug the tube completely, like concrete That may have happened in some zones? Disassemble the Spirovent, they tend to plug badly with that sludge. Same with any other strainers anywhere.

A power flush with a pump cart may salvage some and increase output.
Sludge formation will be an ongoing issue.

Add a cleaner, run for days then flush with a high flow rate pump. In some cases this needs to be done multiple times. I've seen barrels of sludge flushed from non barrier tube systems. Flushing with 12- 20 psi fill water will not be adequate.

While you try this, do a room by room heat load. Possibly there is inadequate fin tube to heat some rooms?

Thank you for taking the time to help.

We were aware of the poly-b when we purchased and knew that it would have to be replaced sooner rather than later. The entire domestic water system was replaced with PEX a few years ago.

My understanding was that Poly-B deteriorated in part due to chlorine so it could potentially last a while in a closed hydronic system that doesn't see high levels of chlorination if new water is not being added frequently. Little did I know the major problem was going to be O2 and corrosion within the system.

As far as heat load - I think the system was overbuilt initially because even with the system working this poorly, a good part of the house gets heated OK (though the boiler is probably working much harder than it should). The living room and bedrooms, unfortunately, are the 2 biggest/longest zones, and thus are the ones struggling the most as there does not seem to be enough flow to service both together when they're calling for heat at the same time.

I have a hydronic expert coming in 10 days to have a look. I'm willing to try a cleaner and powerflush though I am concerned about pressurizing the poly-b as it is known to burst, especially being close to 40 years old.

In the mean time I will relocate the two zone returns I mentioned above, do another flush of the boiler and piping, and will also take the spirovent apart and clean it out.

It is looking more and more likely that we will re-pipe sooner rather than later.

Cherny

mattmia2 said:

Does the boiler stay at 180 when the zones get cold? If it does then it is the flow problem from the sludge @hot_rod mentioned. You could set it up with a heat exchanger and nonferrous components on the plastic tube side but you're probably investing a lot in to borrowed time on the tubing.

Maybe try keeping it filled with inhibitor once you get things cleaned out.

Boiler seems to behave adequately. Heats up to 180 quickly and even when only ONE zone is open (a zone that is "cold"), it takes longer than I think it should for the temperature in the boiler to drop down, again pointing to low flow through the zone, otherwise I'd imagine the temperature would start dropping fairly quickly.

mattmia2

If the boiler is sized properly it should more or less stay at temp with all the zones calling. Does the burner cycle off on high limit?

You can try running hydronic cleaner in there then flushing it while waiting for the contractor, repeat a couple times, that might loosen some stuff up to require less flushing at higher pressure.

Cherny

mattmia2 said:

If the boiler is sized properly it should more or less stay at temp with all the zones calling. Does the burner cycle off on high limit?

You can try running hydronic cleaner in there then flushing it while waiting for the contractor, repeat a couple times, that might loosen some stuff up to require less flushing at higher pressure.

Boiler will come on, get up to 180F quickly, in 1-2 minutes max, then cycle off, then come on again after about 5-10 minutes when the temperature begins to drop (as seen on the digital display).

Hope that answers your question.

Is there a specific cleaner you'd recommend? Would I put that in with a bucket/sump pump hooked up to one of the drains? Thank you.

fentonc

@Cherny - That's how my boiler behaves (similar model, a 140K BTU/hr Cga-5), with all three zones working fine. You didn't say how much baseboard is in each zone, but if you have six zones (and they're gunked up and limiting the flow) and only one is calling for heat, the boiler is probably just adding heat way faster than it can be radiated into the living space. The boiler itself is probably not the problem here.

Cherny

fentonc said:

@Cherny - That's how my boiler behaves (similar model, a 140K BTU/hr Cga-5), with all three zones working fine. You didn't say how much baseboard is in each zone, but if you have six zones (and they're gunked up and limiting the flow) and only one is calling for heat, the boiler is probably just adding heat way faster than it can be radiated into the living space. The boiler itself is probably not the problem here.

Agreed.

The 6 zones have a varying amount of baseboard (a few service single bedrooms, others larger areas). The biggest and most problematic zone covers our living room/dining room/kitchen (about 1100sqft) and has 36ft of 3/4" baseboard which seems adequate.

hot_rod

Cherny said:

mattmia2 said:

If the boiler is sized properly it should more or less stay at temp with all the zones calling. Does the burner cycle off on high limit?

You can try running hydronic cleaner in there then flushing it while waiting for the contractor, repeat a couple times, that might loosen some stuff up to require less flushing at higher pressure.

Boiler will come on, get up to 180F quickly, in 1-2 minutes max, then cycle off, then come on again after about 5-10 minutes when the temperature begins to drop (as seen on the digital display).

Hope that answers your question.

Is there a specific cleaner you'd recommend? Would I put that in with a bucket/sump pump hooked up to one of the drains? Thank you.

Rhomar is an excellent brand, Fernox and Sentinel are other brands. Use a hydronic specific,not just soap or TSP. It’s note a cheap date, I suspect it will require a gallon or more.

I would do a few more water flushes, zone by zone first to get the bulk of the crud out. Then add cleaner to maximize the$$.

If you are going to do this yourself,invest in a 1/2 hp pump like this. This tops out at 40 psi, so you don’t go way over on the pressure, add a pressure gauge at the outlet to watch and adjust.

If you shop for some 3/4” hoses you should be able to flow up to 10 gpm to quickly flush.

A sump pump could be used for fill, but not enough pressure to push through the 3/4 loops.

mattmia2

@hot_rod may have some recommendations on cleaners or what water treatment manufacturers to talk to about what they recommend to clean this up.

Cherny

Thank you all. I just got my hands on a couple of bottles of Hydro-Solv 9100 from a local supplier. I am about to head down to the dungeon and will do the following:
- continue to flush the system back and forth. This time I'm going to use a garden hose from a nearby spigot and see if I can flush the system with a bit higher PSI (around 40-50) than what the fill valve can provide.
- I will be taking apart the Spirovent to clean and inspect and will be replacing it if the element is failing (this seems likely). Can I buy the element that goes inside the Spirovent separately if the casing is in good condition or would I need to replace the entire thing?
- Will be flushing the system again and re-filling with the HydroSolv 9100 and letting the system operate at temperature for a few days and flushing again. I am not seeing a "limit" on how long the cleaner can circulate (only for aluminum boilers which the CGA4 isn't). Please correct me if I'm wrong here.**

Meanwhile we are starting to seriously price out components for the inevitable - a complete re-pipe with newer components and a more maintenance-friendly layout in the boiler room.

Any other suggestions welcome. I appreciate you all!

hot_rod

I think you could circulate for a few days, the "detergent" loses strength just like dish soap as it works.
Run the temperature up as high as you can, the soap works best warmed up.

Make sure you use enough cleaner to do any good.

The garden hose idea works well, just keep an eye on pressure both for the relief valve pop, and also blowing out any boiler gauges.

It can take a day to get a good flush on a system with a lot of heavy sludge in the boiler and pipes. Good flow velocity is the key to getting the mud moving.

Hot_water_fan

We are aware the boiler is marginally sized for the size of this house and we will likely require a secondary heat source. We are thinking of putting in a gas fireplace in our main living area to supplement some BTUs, but we would like to assess this once the hydronic system is working adequately.

Not sure how you came to this conclusion, but agree that the boiler size is probably the least of your worries.

mattmia2

If you can get it flowing you should treat the final fill with corrosion inhibitor to keep it from rusting up again. If you keep testing and replenishing the inhibitor it should keep it from sludging up again. Filling with deionized or distilled water would be a good idea too to keep the chlorides away from the plastic.

Cherny

Hot_water_fan said:

We are aware the boiler is marginally sized for the size of this house and we will likely require a secondary heat source. We are thinking of putting in a gas fireplace in our main living area to supplement some BTUs, but we would like to assess this once the hydronic system is working adequately.

Not sure how you came to this conclusion, but agree that the boiler size is probably the least of your worries.

I could be wrong on this. Based on some simple calculations online, a 3800sqft house in our climate is estimate to require around 120-130K btu and this boiler is rated at 80-105k if I remember correctly.
However I think by improving the building envelope, sealing any obvious air leaks and adding some insulation to the attic we can probably get away with it.

Only way to find out once we get the system up and running properly.

Hot_water_fan

I could be wrong on this. Based on some simple calculations online, a 3800sqft house in our climate is estimate to require around 120-130K btu and this boiler is rated at 80-105k if I remember correctly.
However I think by improving the building envelope, sealing any obvious air leaks and adding some insulation to the attic we can probably get away with it.

Only way to find out once we get the system up and running properly.

Agreed. If the existing boiler turns off during the coldest days, it's not undersized. Online calculators aren't that accurate. Once everything's working, you can reevaluate.

mattmia2

If this is newish construction it will have more insulation and air sealing than a typical structure.

Cherny

mattmia2 said:

If this is newish construction it will have more insulation and air sealing than a typical structure.

It definitely has more insulation than your average 1986 home in this area (2x6 walls instead of 2x4 etc) but there are still quite a few areas that need addressing, but we're getting to them methodically.

JUGHNE

Just for general info on PB tubing.

There was an oxygen barrier version of PB, IIRC it is labeled PBX, the 1/2" OD tubing is red.

I have two thousand plus feet of it buried in my house, in concrete and walls.

Been there since 1995 with CI boiler, pumps, black piping and copper.

Plain raw water and never chlorine.

The water feeder is shut off, seldom have to bump it up.

I upgraded to a modcon and new pumps and could see no problem on the old iron products.

No problems with it yet.....knock on wood.

Cherny

Well everybody, we have found our culprit.

I went down to the boiler room today to do a few more flushes as it was suggested above before pumping HydroSolv 9100 into the system. I also wanted to open the Spirovent and clean it as it was also suggested.

While draining down the system to open the Spirovent, I could not even get all the water out of the system, almost like there was a vacuum when there shouldn't have been as we had 2 taps open in the system. So I decided to slowly crack the Spirovent open to let in some air and you will not believe what I found inside...

A completely congealed mass of hydronic sludge which was creating a complete seal inside the Spirovent housing. As soon as I pulled it out, it immediately gurgled and release the vacuum, draining the remaining water out of the system.




I took the top of the Spirovent housing and took it apart in my shop, getting the spring and float mechanism completely clean. I re-assembled the Spirovent but without the mesh inside as the original mesh was disintegrating and I do not have time today to swap the whole Spirovent as soldering will be required.

I then proceeded to re-assemble, flush the system, with NOTICEABLY better flow through all the zones... except for Zone 6 which continues to have no flow. There is the smallest of trickles getting through. I flushed all zones both ways several times and got quite a bit more sediment out.


Finally filled the system back up with a couple of pints of HydroSolv 9100 and flipped the switch. I could immediately tell water was flowing faster. Pipes got warm very quickly, returns all got equally warm, and the pump is now happily pumping away at close to 0.75amps as it should.




Confirmed every baseboard in the house is HOT and the temperature is coming up quickly!

I will be putting in a new Spirovent if I can't get a cartridge to replace the old one but for now, it is running OK without one and it was even venting a bit of air while I was there watching it, but it may not catch the smaller bubbles.

We will let the HydroSolv run for a few days and do another flush to see where we're at but I'm confident we have solved the issue and can move on to thinking about re-piping for long-term longevity of the system.

Cherny

JUGHNE said:

Just for general info on PB tubing.

There was an oxygen barrier version of PB, IIRC it is labeled PBX, the 1/2" OD tubing is red.

I have two thousand plus feet of it buried in my house, in concrete and walls.

Been there since 1995 with CI boiler, pumps, black piping and copper.

Plain raw water and never chlorine.

The water feeder is shut off, seldom have to bump it up.

I upgraded to a modcon and new pumps and could see no problem on the old iron products.

No problems with it yet.....knock on wood.

That's good info, thanks.

I do however believe we have plain, old Poly-B.

We have already had one pinhole leak in one of the two remaining polyB lines we have going to a bathroom. Granted that sees higher chlorine levels and much higher pressures. Thankfully it did not damage anything, but it has definitely put us on edge. We rent out our basement and with the folks leaving in the next couple of months, we are thinking this may be a good time to get'er done and finally get rid of all the polyB but we will finish doing a cost analysis first and see if it's within our budget.

hot_rod

If you can’t buy a spiro element replacement, buy a new one and swap the element and top end. No need to unsolder the old one

mattmia2

Looks like supplyhouse.com has them. certainly cheaper than buying the whole thing. make sure you get the right one for your model.
https://www.supplyhouse.com/Spirotherm-PJR125IT-Spirovent-Inner-Core-for-1-1-4-Models

might want to make sure the vent isn't leaking to see if you need the top too

mattmia2

Oh, and i prefer the threaded version, rather burn up a $2 adapter than a $150 vent if something goes awry sweating

HomerJSmith

First things first, if the drawing of your sys is correct, the expansion tank is in the wrong location. You are essentially pumping into the Xtank. You should be pumping away from the Xtank. Secondly, the shortest run will have the most flow. Possibly, zone 6 is starved for flow. There are no balancing valves on the sys to balance all the zones so that you have equal flow in all of them when more than one zone calls for heat. Thirdly, zoning with zone valves, a fixed speed pump is not the best. A ECM variable speed pump is a better solution.

I have been in your situation with a mucked up sys. I guarantee that the pump impeller is mucked up as well which would interfere with the flow thru the sys. I sandblast the Spirovent element to clean it. It is stainless steel and it works great. Clean what ever you can out of the Spirovent body. I replaced the float apparatus, too.

I use a garden pump to flush these sys. I attach a garden hose to the sys which goes outside or into a drain and I pump clear water thru each loop with the garden pump until the water runs clear before I add any cleaner to the sys. I run the sys for several days with the cleaner, drain the sys and repeat the process. With sys like yours, I have had to do it 3 or 4 times. I then add distilled or de-ionized water and buffer the PH to about 8-8.5.

Check the age of the Xtank.

If it was my sys, I would change the location of the Xtank, change the pump the an ECM pump, and add balancing valve to each zone.
https://www.supplyhouse.com/Grundfos-99163906-ALPHA2-15-55F-LC-Cast-Iron-Circulator-Pump-w-Line-Cord?_br_psugg_q=alpha2+26-99
https://www.supplyhouse.com/Caleffi-132552A-3-4-NPT-QuickSetter-Balancing-Valve-w-Flow-Meter
https://www.supplyhouse.com/Amtrol-102-1-30-Extrol-EX-30-Expansion-Tank-4-4-Gallon-Volume
https://www.supplyhouse.com/Spirotherm-PJR125IT-Spirovent-Inner-Core-for-1-1-4-Models
https://www.lowes.com/pd/Utilitech-1-HP-Stainless-Steel-Lawn-Pump/1000678113

hot_rod

HomerJSmith said:

First things first, if the drawing of your sys is correct, the expansion tank is in the wrong location. You are essentially pumping into the Xtank. You should be pumping away from the Xtank. Secondly, the shortest run will have the most flow. Possibly, zone 6 is starved for flow. There are no balancing valves on the sys to balance all the zones so that you have equal flow in all of them when more than one zone calls for heat. Thirdly, zoning with zone valves, a fixed speed pump is not the best. A ECM variable speed pump is a better solution.

I have been in your situation with a mucked up sys. I guarantee that the pump impeller is mucked up as well which would interfere with the flow thru the sys. I sandblast the Spirovent element to clean it. It is stainless steel and it works great. Clean what ever you can out of the Spirovent body. I replaced the float apparatus, too.

I use a garden pump to flush these sys. I attach a garden hose to the sys which goes outside or into a drain and I pump clear water thru each loop with the garden pump until the water runs clear before I add any cleaner to the sys. I run the sys for several days with the cleaner, drain the sys and repeat the process. With sys like yours, I have had to do it 3 or 4 times. I then add distilled or de-ionized water and buffer the PH to about 8-8.5.

Check the age of the Xtank.

If it was my sys, I would change the location of the Xtank, change the pump the an ECM pump, and add balancing valve to each zone.
https://www.supplyhouse.com/Grundfos-99163906-ALPHA2-15-55F-LC-Cast-Iron-Circulator-Pump-w-Line-Cord?_br_psugg_q=alpha2+26-99
https://www.supplyhouse.com/Caleffi-132552A-3-4-NPT-QuickSetter-Balancing-Valve-w-Flow-Meter
https://www.supplyhouse.com/Amtrol-102-1-30-Extrol-EX-30-Expansion-Tank-4-4-Gallon-Volume
https://www.supplyhouse.com/Spirotherm-PJR125IT-Spirovent-Inner-Core-for-1-1-4-Models
https://www.lowes.com/pd/Utilitech-1-HP-Stainless-Steel-Lawn-Pump/1000678113

I believe the coalescing media in that spiro is copper. One more reason to keep ph in line. I have seen them dissolve in solar systems where the ph drops when glycol goes south.

HomerJSmith

Could be copper, I may have been thinking of Supervent although I have a Jr element on the shelf and it is stainless as I remember.

hot_rod

HomerJSmith said:

Could be copper, I may have been thinking of Supervent although I have a Jr element on the shelf and it is stainless as I remember.

Tin coated copper as far as I know. It's basically their element that they use in baseboard heat instead of fins.
Maybe the larger welded steel versions are stainless.

Cherny

HomerJSmith said:

First things first, if the drawing of your sys is correct, the expansion tank is in the wrong location. You are essentially pumping into the Xtank. You should be pumping away from the Xtank. Secondly, the shortest run will have the most flow. Possibly, zone 6 is starved for flow. There are no balancing valves on the sys to balance all the zones so that you have equal flow in all of them when more than one zone calls for heat. Thirdly, zoning with zone valves, a fixed speed pump is not the best. A ECM variable speed pump is a better solution.

Agreed on all your assessments and suggestions, except for Zone 6 being starved for flow. Unfortunately, even with all other zones manually shut off (at the ball valves located after the zone valves), there is no flow through that zone. I suspect the line is either kinked or plugged with muck. Perhaps coincidentally, this zone is the lowest point in the system, so perhaps it accumulated more sediment than the rest of the system.

My plan is to put a tap and ball valve at either end of this zone soon so we can try to flush it with higher pressures while completely isolated to see if we can clear it out without risking damage to the rest of the system if we accidentally over pressurize. I am concerned about putting more than 20-30 psi into the polyB.

We are going to be re-piping the system eventually and it would be nice to incorporate flow gauges and zone balancing valves, however I have to say the system has been working very well now for the past 24 hours since clearing the Spirovent plug.

What is the benefit of an ECM variable speed pump other than perhaps slightly lower electrical consumption when higher flows are not needed to service multiple zones? Right now, even with a single zone calling for heat, the 15-58 is likely pumping more than needed, but it does not appear to be causing any issues - no noise, baseboards get very hot, etc. Should we be concerned that there will be increased wear and tear on the copper pipe with flow that is unnecessarily high?

HomerJSmith said:

I have been in your situation with a mucked up sys. I guarantee that the pump impeller is mucked up as well which would interfere with the flow thru the sys. I sandblast the Spirovent element to clean it. It is stainless steel and it works great. Clean what ever you can out of the Spirovent body. I replaced the float apparatus, too.

The pump was replaced about 10 days ago as I suspected our issues were being caused by a failing pump. The pump was mucked up but it was not as bad as you'd think. It was simply being throttled by pumping against that plug at the Spirovent, as if it was pumping through a straw. The impeller must have been spinning but water had nowhere to go. I will be overhauling the old pump and keeping it around as a backup.

The Spiro element is just completely gummed up and parts of it are basically falling apart from corrosion so it's going in the garbage. I have ordered a new one for about $20 which should be here in a few days. Right now the system is running fine with an empty Spirovent.

HomerJSmith said:

I use a garden pump to flush these sys. I attach a garden hose to the sys which goes outside or into a drain and I pump clear water thru each loop with the garden pump until the water runs clear before I add any cleaner to the sys. I run the sys for several days with the cleaner, drain the sys and repeat the process. With sys like yours, I have had to do it 3 or 4 times. I then add distilled or de-ionized water and buffer the PH to about 8-8.5.

Check the age of the Xtank.

If it was my sys, I would change the location of the Xtank, change the pump the an ECM pump, and add balancing valve to each zone.
https://www.supplyhouse.com/Grundfos-99163906-ALPHA2-15-55F-LC-Cast-Iron-Circulator-Pump-w-Line-Cord?_br_psugg_q=alpha2+26-99
https://www.supplyhouse.com/Caleffi-132552A-3-4-NPT-QuickSetter-Balancing-Valve-w-Flow-Meter
https://www.supplyhouse.com/Amtrol-102-1-30-Extrol-EX-30-Expansion-Tank-4-4-Gallon-Volume
https://www.supplyhouse.com/Spirotherm-PJR125IT-Spirovent-Inner-Core-for-1-1-4-Models
https://www.lowes.com/pd/Utilitech-1-HP-Stainless-Steel-Lawn-Pump/1000678113

Appreciate your suggestions and will definitely incorporate those into our design for the new system.

I may have to invest in a better pump to maintain the system. I currently have a small emergency sump pump in case our basement ever takes on water but at only 1/4HP it is not enough to power flush.

The expansion tank is a few years old but holds pressure and does not appear to be flooded. We will replace it when we re-pipe, and will definitely relocate to the return side. I don't think it's worth doing right now, only to tear everything down in a few months. Things appear to be working well enough for right now but I will keep an eye on things.

GGross

@Cherny

That is a fantastic lump of sludge, probably felt great getting that out of your boiler system. Good job

pedmec

HOLY COW on the spirovent.

How high is zone #6 in regards to height above the fill valve location. Just wondering if you have enough pressure in your system to flood zone #6.

Cherny

pedmec said:

HOLY COW on the spirovent. How high is zone #6 in regards to height above the fill valve location. Just wondering if you have enough pressure in your system to flood zone #6.

The entire zone is below the boiler and fill valve. About 100ft long feeding one 8ft baseboard.

Like I said above, even city water pressure won't flow more than a slight trickle (forwards or backwards) through the zone.

When I took off the baseboard air vent in the bedroom a few months ago, I could see sludge similar to what I found inside the Spirovent.

Cherny

GGross said:

@Cherny That is a fantastic lump of sludge, probably felt great getting that out of your boiler system. Good job

The sound it made when I finally pried it out and it released suction was amazing. I knew right away that was IT.

mattmia2

I think the thing to do with the zone that is only a trickle is to isolate it and try more aggressive chemicals to dissolve the sludge and see if you can flush it out after you loosen that up. If it is flowing a little you can get chemical in there.

The wet rotor circulator will tend to collect the magnetic iron particles, it isn't great for the bearings in the circulator.

Cherny

mattmia2 said:

I think the thing to do with the zone that is only a trickle is to isolate it and try more aggressive chemicals to dissolve the sludge and see if you can flush it out after you loosen that up. If it is flowing a little you can get chemical in there. The wet rotor circulator will tend to collect the magnetic iron particles, it isn't great for the bearings in the circulator.

Do you have any suggestions for something more aggressive than Hydro-Solv?

hot_rod

It’s more about getting good flow, not so much dissolving the sludge. The sludge is not stuck or adhered to the pipe it’s just a heavy particle makeup settled in the tube. Pressure and flow is the key. Like washing a pile of dirt off your sidewalk🥸, or a thick layer of mud off your truck adding soap wouldn’t help move the dirt.

i use the Rhomar after all the heavy sludge is out, to clean off the leftover film inside the boiler, pipes, heat emitters, it would be nice to get those surfaces back to clean metal for best transfer, that is where the Rhomar excels

If you can’t get flow at all, the Rhomar may not help

Cherny

MikeAmann said:

The entire zone is below the boiler and fill valve. About 100ft long feeding one 8ft baseboard.

Like I said above, even city water pressure won't flow more than a slight trickle (forwards or backwards) through the zone.

When I took off the baseboard air vent in the bedroom a few months ago, I could see sludge similar to what I found inside the Spirovent.

OMG, that sludge! Zone 6 at the air vent - are you able to inject your flushing water here and try to force the sludge out in either direction?

That is an interesting idea. Definitely worth a shot.

Are those air vents at the copper elbows a standard pipe thread? 1/4 in? I can try and see if I can Frankenstein an adapter together to hook up a hose to it.

pedmec

Not to scare you but that sludge is a bad sign. O2 eating up ferrous materials like your boiler. Can't imagine what the cast iron heat exchanger looks like. Have to imagined its thinned out. Normally i wouldn't say that they don't make them like they use to is a problem but this might be the exception. They just don't make heat exchangers as thick as they use too.

Cherny

pedmec said:

Not to scare you but that sludge is a bad sign. O2 eating up ferrous materials like your boiler. Can't imagine what the cast iron heat exchanger looks like. Have to imagined its thinned out. Normally i wouldn't say that they don't make them like they use to is a problem but this might be the exception. They just don't make heat exchangers as thick as they use too.

We are well aware what the sludge is and where it came from. It is in our near future plans to re-pipe the system with PEX to eliminate the possibility of leaks as well as to eliminate the corrosion caused by the crappy polyB. It is entirely possible, I suppose, that the boiler, which is only a few years old, will have a lower life expectancy. It is what it is.

The system has clearly not been maintained up until now so all we can do is look after it from now on, hope that a bit of TLC will extend the life of all components, and deal with problems as they arise moving forward.