Safely Re-Position Expansion Tank In System

AnthVale · September 21

Many on here instructed me to move my expansion tank to the inlet of my circulator pump so it could be "pumped away." After a good bit of research, this is clearly the move…

I have already powered down the entire system electronically and drained parts of it to add a new zone to the house and rebuild the circulator pump which had failing gaskets.

So, I should be able to simply (safely?) unscrew the expansion tank, correct?

Here are current and proposed diagrams after speaking with @hot_rod.

The proposed has the changes in red.

My questions are essentially:

1: The lines are unpressurized and have little water, I can safely unscrew this tank, correct?

2: When I take the tank off, should I check the pressure matches the feed or boiler, or what?

3: My water heater has no tank, but does have a PRV. Is that ok or should I be adding a tank there? There's no check valve between it and the town's water so wouldn't that make it an open system

4: While the system is down and unpressurized. Are there any other immediate recommendations this system could have? I just need to get through the winter so anything that's a bit more challenging can wait til next summer but I would love to know if there's anything urgent missing. I just bought the house and it was a **** show.

Thanks,

mattmia2 · September 21

Put a drain between the isolation valve for the expansion tank and the tank so you can relieve the pressure to check the precharge.

The air side of the expansion tank should be set to the cold fill pressure of the system with the tank disconnected from the system.

Ironman · September 21

Regarding the domestic tank: your system needs one since the PRV closes when there’s no flow through it and the water needs a place to expand when heated.

AnthVale · September 21

@Ironman Edit..I meant to say pressure relif valve, not pressure reducing valve, when I said PRV in my original post.

With that wouldn't that mean it's an open system and could back up into city water?

@mattmia2 Something like this (see diagram)?

So, can I safely unscrew the tank from where it is to where I want to move it? You can see the two bottom images of where the tank is and where it's gonna be moved too as well.

Also, how do I know what the fill valve is set to? Is it always what the manufacturer sets it at, or can it be adjusted? The label says 12-15 PSI.

Thanks,

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Jamie Hall · September 21

Can you safely unscrew the tank? Yes. But. You may get rather wet. Perhaps more to the point, if there is still water in the tank — which there may be — it will be much heavier than you expect it to be. I, at least, wouldn't attempt it without a helper to take the weight.

AnthVale · September 21

@So, there's a valve between the circ pup and boiler that's not shown on the diagram that's at the bottom of that pipe below the pump. When I was servicing the pump I drained from there and a lot of water came out. Way more than what I imagined being in the pipe from the pump to the drain valve. I'm guessing the entire boiler up to the air-scoop/xtank also drained.

Would this have drained the xtank possibly?

@Jamie Hall thank you

You can see this drain valve under the pump here:

AnthVale · September 21

EdTheHeaterMan · September 24

You might try this diagram

So your picture might look more like this

be sure to keep the 18" approach pipe with that type of air separator.

AnthVale · September 24

I'm going to guess that there's about 18 in to the right of that expansion tank as is right now. So I wouldn't be able to nudge it over a bit like you did in the photo.

It would be really tight to get the circulator pump to the left of it in that photo. Certainly possible, but, I would need to rip out all that copper and go to threaded steel pipe. It would be a good sized project but if it's worth it I'll do it.

I also Just spent $50 on new parts to move the expansion tank above the circulator pump on the inlet side of where the circ pump currently is because that's what everybody was telling me to do lol.

How much better or worse is it to keep it where it is now, versus where you just mentioned, versus where I was just planning to put it (before circ pump cold return side).

My system is currently off with a lot of water drained and no pressure inside so right now would probably be the time if it's necessary.

Thanks @EdTheHeaterMan

hot_rod · September 24

The change you made will improve the system. If you go deeper I would use an air separator instead of that iron purger

There is no straight pipe requirement and they are 97% efficient with a sep like the Discal

AnthVale · September 24

Thanks, @hot_rod. I haven't done anything yet besides buy all the parts to do what you and the other gentleman had mentioned last week (put tank before circ pump on return line).

It seems the RIGHT / Most Efficient (correct me if I'm wrong) way to do this is to return everything I purchased to the supplyhouse, keep the tank where it is, and find a way to get the circulator pump and the main feed re-routed to the Flow side…everything I'm reading is saying the best setup is to have the circ pulling away from the tank on the Flow side while also having the cities main feed also being on the flow side.

Are you saying that if I do try to move the circ pump to the flow side, I could use something like a Discal air separator to save space since there's no 18" straight pipe requirement?

Thanks,

EdTheHeaterMan · September 24

@AnthVale there are some basic laws of the physics of how water and air interact. Without going to far into that (look up Boyles Law on dissolved gasses) lets just say that to get the best performance from an air vent, you want to place that vent where the hottest temperature and the lowest pressure is. In all your original diagrams, that place does not exist.

The lowest pressure is the pump inlet. The highest temperature is at the boiler supply pipe (or actually at the top of the boiler just before it exits the boiler). Those two places are at different locations on your system and you diagrams. The only way to get both the lowest pressure and the highest temperature to happen in the same place is to put the circulator pump on the hot supply pipe, as close to the boiler as you can.

By using a micro-bubble type of air vent at that location, you add one more air removing device the increase the efficiency of getting the air to vent there. The micro bubbles that form, as a result of the low pressure and the high temperature, will encounter a reduction in velocity and an obstruction (the screen) that will cause those tiny bubbles to crash into each other and form larger bubbles. Those larger bubbles in the low velocity chamber will allow gravity to do the job of making the lighter air and the heavier water to cause the air to rise to the top of the vent and exit the system.

I think that Hot Rod Bob would agree with that suggestion. But since it is not our money that is going into this project, getting parts of the solution in place at lower cost to you is better than nothing. I however believe that you can do this economically with the parts you already own. If you want to spring for a Spirovent or Discal air separator, then good for you. I recommend it!

hot_rod · September 24

yeah, how much time and money you want to invest to get how much better of a system?

There is no problem with the pump on the return side, pumping into the boiler like you have, Ideally the tank is connected upstream. The air eliminator is best at the hottest point, secondly at the lowest pressure

Boiler manufacturers sold and shipped boilers with pumps on the return for decades now, some still do

AnthVale · September 25

This all sounds good. Thanks again. I have all the time, but not a lot of money. But, I don't think any of these upgrades will break the bank and like Ed said, I will be able to use a lot of the stuff I already ordered or already have to finish the job right.

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Three Questions:

1: Does it matter how close the circ pump is to the airscoop? I think I can squeeze this pump right here. I think I can fit this without moving the airscoop to the right (which would make that span less than 18").

2: Out of curiousity (don't think I'll do this) but, can the airscoop go on the vertical pipe coming out of the back of the boiler shown above (the 6 foot vertical)? I'm guessing I'd need to move the air vent if that was the case. Perhaps to the plugged T area…

3: As for the Spirovent or Discal air separator, is this replacing the airscoop or being added to the system in addition? I do have that plugged T before the Airscoop which can be seen in the photos and the diagram. Could this spot be used in any way or do these need to be inline? I may ommit this for now.

Anyways, I think I will be able to fit the circ pump to the left of where the airscoop currently is, then I can bring the main feed in and attach it under the airscoop like @EdTheHeaterMan had shown in his diagram update.

Thanks guys. This is deff a learning experience. I've done more research and forum talking on plumbing/heating the past month it's been a lot of fun. I want to thank you again! With your help I was able to add a new zone to my house and do all these upgrades.

Cheers,

PC7060 · September 25

https://forum.heatinghelp.com/discussion/comment/1811742#Comment_1811742

1: Does it matter how close the circ pump is to the airscoop? I think I can squeeze this pump right here. I think I can fit this without moving the airscoop to the right (which would make that span less than 18").

I believe there is a minimum distance, but I don't recall eact number

2: Out of curiousity (don't think I'll do this) but, can the airscoop go on the vertical pipe coming out of the back of the boiler shown above (the 6 foot vertical)? I'm guessing I'd need to move the air vent if that was the case. Perhaps to the plugged T area…

The airscoop need to be oriented horizontally

3: As for the Spirovent or Discal air separator, is this replacing the airscoop or being added to the system in addition? I do have that plugged T before the Airscoop which can be seen in the photos and the diagram. Could this spot be used in any way or do these need to be inline? I may ommit this for now.

The air separator would replace the scoop. That would be optimal solution as it eliminates the minimum separation requirements from pipe bends and pumps

EdTheHeaterMan · September 25

Does not matter, you can use a close nipple to the circulator flange.
NO. Your air scoop works on gravity. air is lighter than water and the air vent hole must be at the top. Bu placing that scoop on a vertical pipe, the air collecting chamber will not be on top, it will be on the side.
Spirovent or Discal will replace the air scoop, you don't need both.

So, to be clear, If you are thinking of moving the pump to the proposed location, you do not need to purchase a Discal or Spirovent. You can use the air scoop you have. Just use a quality air vent in the top fitting.

If you are going to purchase the Discal anyway, then you can eliminate the Air Scoop you have.

Either choice, pump away from the expansion tank on the supply side near boiler piping

AnthVale · September 25

Awesome, I purchased some close nipples for the previous plan so we're good to go. Ok, so I will get that circ pump upstream of the air scoop/tank so it's pulling away.

Before I start, is there a spot where the main water feed is "most efficient"? It will plug in between the tank and airscoop unless you think there's a better place for that.

I do want to replace that air vent. Which would you recommend?

One last thing, I have one of these on hand (see below). If I place this between the tank and scoop can I use the Hose threaded side to attach the main feed? Or, do I want to leave this when it comes time to drain and replace tank?

Screen Shot 2024-09-25 at 1.28.34 PM.png

Cheers,

EdTheHeaterMan · September 25

Best location for water feed is at the expansion tank. I like those fittings that make it easy to isolate the tank from the system so you can check the air pressure whit the tank disconnected from the system.

https://www.supplyhouse.com/Webstone-41672-1-2-Pro-Pal-Full-Port-Brass-Ball-Valve-w-Hi-Flow-Hose-Drain-600-WOG?_br_psugg_q=expansion+tank+valve

AnthVale · September 25

Interesting. I like the one you shared. Brilliant. I'm going to return mine and get the one you shared.

I will report back and thanks again!

AnthVale · September 28

Hey, @EdTheHeaterMan

Does it matter if the instructions for my water feed regulator mention putting it on the return side? Is this just older way to do it?

Screenshot_20240928_165058_Drive.jpg

Also, how would one check/adjust the pressure on one of these? I want to ensure it matches the expansion tank.

Thanks again,

EdTheHeaterMan · September 28

I actually see a mistake on that document and there is no reference to adding water to the return side in any text. Only the old illustration that is referencing a boiler fitting or Tee on the supply side and that Tee piped to an expansion tank that is above the boiler (probably in the rafters) So I would say that is old instructions from the original design and build of that part in the 1950s.

If you look at the illustration on page 1, there are two Pressure Relief Valves, and no Pressure Reducing Valve according the that drawing..

In the 1950 most boiler manufacturers recommended the circulator pump be mounted on the return. We didn't get smart enough to put the circulator pumps on the supply pipe until the 1980s

And if your boiler is equipped with a circulator pump on the return, what side of the pump should place the water feed pipe? If you select the wrong side, you may cause other problems, based on the lower inlet pressure of the pump that feeder can actually add more water to the system after you have everything set just right.

Ask me how I know this?

AnthVale · September 28

Hope whatever happened wasn't too bad haha!

That is interesting and I'm gonna bet you're right about the instructions.

I think I misread them anywho. When I saw cold water supply I thought return. Long day haha.

I'm currently replumbing things now the way you have it in the diagram you adjusted for me.

Thanks again,

AnthVale · October 2

Ok, I've arrived at this. Thanks for all your help @EdTheHeaterMan

My question is, what's the procedure for re-adding water to the system? Here's what I've done so far. I've added a new zone to the system, added a 4' baseboard radiator to another zone, and moved the circ pump/main feed over to the flow side.

Here is my current thought:

I want to ensure the pressure after the water pressure regulator matches the tank, so I thought I could close the valve after the gauge and start by adding water to that point. Then I can read the pressure beforehand in that small area first. Then I can add air to my tank to match, and install after. I did read somewhere else that this could not be the true pressure, but it will be close enough?

Then, I thought I would purge all the zones. Two were worked on and the third I feel why not. It's a new house to me I have no idea what maintenance has been done.

Is there any procedures, order of operations, tips or tricks I should know before adding water back in to the system? Open all valves and let it rip? Only have new zone open and fill that first? Any advice would be greatly appreciated.

Thanks,

EdTheHeaterMan · October 2

This is the sequence of operation for filling the boiler.

Measure the highest point in the system. If you have 3 floors (2 story plus basement). That might be 21 feet from the location of the gauge in the boiler in the basement to the top radiator.
Calculate the minimum Static Pressure. Using that number, divide it by 2.33. Then add 3 to that number. That will be the minimum PSI your need to get the water to the top of the system. eg: (21 ÷ 2.33 = 9). 9 + 3 = 12 So you need 12 PSI static pressure for your home. If you have 3 story home and your highest radiator is 30 feet above the gauge, then the math looks like this. (30 ÷ 2.33 = 12.8) or about 13. 13 + 3 = 16. So you need 16 PSI. NOTE: Never use a static pressure below 12 PSI
Adjust the Expansion Tank Charge. With the tank disconnected or isolated from the system, and no water in the tank, fill with compressed air to 12 PSI. (or what ever you calculate as your minimum Static Pressure in step 2. above.)
Connect the expansion tank to the system. This can be done by closing the drain valve near the expansion tank, then opening the valve to the system.
Fill the system with water until the boiler gauge reaches 12 PSI. Now you have the boiler filled with water and some air in the radiators.
Connect a hose to the purge valve for the zone that you wish to remove the air from, then close the isolation valve just below the purge valve. This will cause the flow from the boiler thru the zone loop you are purging to exit at the purge valve when you open it
Increase the boiler pressure to about 25 PSI. that is low enough to prevent the pressure relief valve from opening. You can increase the boiler pressure using the manual fill valve lever on your auto feen valve
Open the purge valve while keeping an eye on the boiler gauge so the pressure does not rise above 25 PSI and allowing water to flow. If the boiler gauge dropw below 12 PSI, then kink the garden hose or close the purge valve until you get the boiler pressure to get to 25 PSI. This will insure there is enough foot per minute water speed to cause any air to be pushed down from the upper floors to the purge valve.
Once you get a steady flow of water with no air out of the purge valve, close the purge valve and set the fast fill lever to automatic.
Repeat steps 6. thru 9. for each of the other zones, starting with the lowest floor and continuing until you get the air out of the highest floor.
When you have all the air purged then close all the necessary purge valves, open all the necessary isolation valves and drain the water from the boiler (from the last zone purged) until the boiler pressure is at or just below the static pressure setting.

Now you are ready to operate the system

EdTheHeaterMan · October 2

As far as your diagram is concerned, the Air Scoop is shown on a vertical pipe, but I assume you know that it needs to be on a horizontal pipe for it to work. Unless you are purchasing the Caleffi 1" Union DISCAL Rotating Collar Air Separator that is made to be mounted on a vertical pipe.

The air scoop you have pictured above in previous post, with 18" approach pipe, MUST be horizontal.

Then to do step 3 above use the expansion tank valve to isolate it from the system and get all the water out of the tank. If you can't do that, then you may have the valve installed upside down.

AnthVale · October 3

@EdTheHeaterMan thanks! This all sounds great. Excited to turn it all on.

The highest point is no more than 10 feet so I'll go with 12 psi.

There is 18" of horizontal 1-1/4" steel leading to the air scoop.

Thanks!

AnthVale · October 3

Ok, so I opened the valve before the backflow preventer to let the main supply in and left the valve closed after the gauge. The gauge is now reading 17psi. The nut on top of the regulator is all the way backed off.

This was after I took the water feed regulator apart. Surprisingly, it was pretty clean inside. However, the filter part with the moving piston through the middle was very locked up. There was no play in the diaphragm at all. I got it free with a tiny bit of W240, and it is moving freely but still seemed stiffer than it would be directly from the factory.

Is there another way to set these, or do you think this one is done? And, if it does need to be replaced, would I buy a new one can I just run the system at 17psi ok? It was at 17psi when I bought the house now that I remember.

The rebuild kit is expired on watts website. It's a Watts SB1156F

Thanks, @EdTheHeaterMan

https://www.watts.com/products/plumbing-flow-control-solutions/hydronic-steam-heating/boiler-feed-water-pressure-regulators/1156f

EdTheHeaterMan · October 3

Try it against a larger volume of water, with the adjustment screw all the way backed out. If it still goes to 17 PSI, then replace it.

hot_rod · October 4

A good chance the pressure may slowly creep up if the fill valve is not sealing tightly. There is a seat and washer not unlike a faucet shutoff. The washers get hard and brittle and the seats can get a nick in them

Id replace the entire assembly, fill valve and backflow. Caleffi 573 for example😉

Safely Re-Position Expansion Tank In System

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