Red water and nasty residue inside circulator of my Radiant Heating System.

JackW

I saw red water in my clear Y strainer about halfway through the heating system. So I drained the system, cleaned the Y strainer, took all the adjusters off the manifolds, and soaked them in diluted CLR. As you can see in the pictures, this stuff is everywhere, and from the looks of the circulator, pretty bad. I have a Rhomar cleaning kit coming, but it's back-ordered till June. I assume this is iron residue; what could be generating this amount of residue? Is there anything I can do to prevent this from occurring in the future, and any other recommendations for cleaning this out of the system? Any help will be greatly appreciated.

Jack

hot_rod

Oxygen is getting into the system somewhere, somehow. Any small leaks that are allowing new, fresh, oxygenated water into the system?  

Hydronic chemicals have some oxygen inhibitor, but cannot handle large amounts of ongoing ingress.

Air vents can allow air/ oxygen in. Non barrier tubing also.

JackW

Thank you for your input. I have a couple of fittings that need to be redone; there is white crusty buildup around the threads. Also, all the PEX, except for about three feet going to the manifolds, are encased in concrete. At the start of the season, I did have trouble getting all the air out of the system, but after bleeding it several times, the pressure stayed constant throughout the whole season. Below is a picture of the Rhomar kit I have coming, will it clean my system, or is there a better method?
Thanks,
Jack

Larry Weingarten

Hi, Are there any markings on the PEX tubing that you can post a photo of? It's important to figure out how oxygen is getting into the system. Any treatment is just a band-aid if oxygen is getting in. Photos of the piping/controls would be nice to see as well.

Yours, Larry

hot_rod

Do a power purge of the system first to get as much crap out before you put the cleaner in. Do you have some good purge points, possibly some purge valves at the manifolds?  It takes high flow, high pressure to flush any heavy rust particles out

Flush loops one by one until they run clear, then add cleaner and run it hot for a day to allow the detergent to work 

A few pics may help determine what you have for purging valves.

JackW

@hot_rod, here are a couple of pictures of the whole system. The system isn't particularly easy to bleed air from when first re-filled, it takes several tries to get all the air out. Any suggestions on valve placement to make this process easier, now would be the time to do it. Thanks for your help.

Jack

JackW

@Larry Weingarten, here are some pictures of the 1/2" pex I used, I hope you can read them. Thanks for your input.

Jack

Larry Weingarten

Hi, I found this site: https://canarsee.com/learning-center/pex-pipe-markings which explains the markings on PEX. Yours has a number, F2023, which suggests it may not be barrier type PEX. If so, this would allow oxygen into the system. Also, CPI Dura PEX had problems with fittings, and Nibco, who acquired CPI was sued because of failures. There is a lot on the web about this. I think it might be good to verify what you have, and if it's non-barrier, then getting rid of all ferrous components would be something to consider.

Yours, Larry

hot_rod

I think Larry is correct, DuraPex was also sold by Watts. A classic example of how non barrier pex allows O2 into a system. Even a low temperature system!

Is it a glycol system by chance?

That is a very nice panel, did it come with the tubing? How old is it? If it was sold as a package they should have include stainless body circulators, assuming it is non barrier tube. You need the entire system to be non ferrous. It looks like a domestic water expansion tank based on the connection size, so that should be fine, it is a coated steel tank.

So with a very small amount of ferrous surface the corrosion, rust and hematite formation on the ferrous parts will be significant. The relative area effect.

The circulators and the iron flanges need to go. Either stainless or composite body circs. Threaded brass flanges may work, to replace the iron ones, if you can still find them.

OR, keep adding oxygen scavenger chemicals, yearly probably.

Where are you located? In some areas there are incentives/ rebates to install high efficiency circulators. Maybe get two birds with one stone, ECM and stainless circs.

www.dsireusa.org, click on your state

hot_rod

Are you on a private well? Hows the water, any color or odor?

I've only experienced it twice but I had two system that had iron bacteria. The water in the radiant had a real harsh rotten egg smell. You could carve away the iron pump body with a pocket knife, the bacteria was dissolving all the ferrous parts.

These were brand new homes with radiant, turns out the well driller had the bacteria on his drill rods and was depositing it in new wells he drilled.

JackW

@Larry Weingarten, thanks for posting that site, I'll take a look at it, I might learn something.

JackW

@hot_rod. No, it's not a glycol system. I installed this two-zone system in 2005. Initially, I worked with a guy from CPI; they drew up the floor plan for me because I bought one of their panels at Menards along with the PEX and accessories. I initially used the wrong heating source and then switched to a 30-gallon water heater. I never had the system plumbed correctly for two zones from the start. When the water heater died, I decided it was time to re-do the whole system in 2019. I started from scratch, and with a lot of help from all of you guys here on the website, I re-plumbed the entire system, and it works great. The old system had copper piping and different circs, but I never had all of the rust problems.
I don't know if the expansion tank is coated or not; I'll have to look into that. I'll also have to look at the circs to see why they never rusted the system up like these are; they are single speed but weren't stainless. I know non-ferrous circs are very expensive. Are oxygen scavenger chemicals a viable option? I'm in NW, Ohio.

Thanks for your help,

hot_rod

the hydronic system inhibitors contain oxygen scavengers, Rhomar, Fernox, Adey, etc. But the scavengers get depleted, then you have to boost them up. It really depends on how much oxygen is getting in.
The companies  that sell those steel outdoor wood boilers sell oxygen scavenging chemicals I doubt they have all the same ingredients as hydronic conditioners, based on the price.

That seems like a lot of rust and build up for just a few years.

In a true, sealed hydronic system the O2 is consumed quickly by oxidizing any ferrous metal, typically just a very thin coating on the pump bodies if you take them apart.

After the O2 is consumed you have “dead” water, no or low O2, and corrosion stops. All closed systems let some O2 in around seals, packings, gaskets, etc.

Id expect that much corrosion on a high temperature non barrier tube system. The O2 ingress increases with temperature The original rubber tube, fin tube baseboard systems running 180F SWT would corrode like that in one heating season, pinhole expansion tanks in a few months!

Paul Pollets

You may want to separate the system water from the boiler water with a flat plate heat exchanger using a SS pump on the system side. A dirt/mag separator will also help. Non-barrier tubing will continuously affect the system and cause major issues down the road.

JackW

@hot_rod, what is so strange is I never had this problem until I redid the whole system in 2019. All the pex, except for what you see, is encased in concrete, so replacing it isn't an option. I can't believe the little bit of exposed pex would allow that much oxygen into the system; it never did before. The more I think about it, this just happened this heating season. I've had this up and running for three years now. If that much oxygen was infiltrating my system, wouldn't it be difficult to maintain constant pressure? I have a couple of fitting with white crust built up around them; could that be the problem? If I decide to change the circulators, what do you recommend I go with?

JackW

@Paul Pollets I never had the rust problem until this year. I redid the whole system in 2019 but didn't have any issues with rust until this last heating season. The only exposed pex is what you see coming out of the concrete. I have a couple of fittings that I need to take care of, maybe thats' where the problem lies. Thanks for your help.

Canucker

JackW said:

@Paul Pollets I never had the rust problem until this year. I redid the whole system in 2019 but didn't have any issues with rust until this last heating season. The only exposed pex is what you see coming out of the concrete. I have a couple of fittings that I need to take care of, maybe thats' where the problem lies. Thanks for your help.

Did you say you were using a water heater up to 2019? Perhaps your anode rod was getting sacrificed until you changed it, then your pumps became the target of the oxygen diffusion thereafter

HomerJSmith

Have your water tested. Acidic tending ? It's important to have good water with a balanced PH.

hot_rod

Air gets through concrete, tube even completely surrounded by concrete still see oxygen diffusion.  We are talking molecular level o2
The only way rust continues like that is a constant supply of O2

JackW

@Paul Pollets I'm using a wall-mounted boiler now.

JackW

@HomerJSmith I plan to; right now, I've drained the system and am flushing it out.

JackW

@hot_rod, well, since I can't do anything about the pex, my choices boil down to flushing the system every year or replacing everything that rusts with brass or stainless. Ouch.

JackW

@hot_rod. I just pulled the two pumps off the shelf from my original setup, and low and behold, they are single-speed brass pumps. I couldn't believe it, I had no idea. So I'm going to replace the cast iron circs with these two, plus one more that I'll have to buy. My question is, the brass pumps didn't come with check valves as the cast iron circs did. Do I need to install check valves above the brass circs?
Thanks,
Jack

JAdams

Another thing to look at is the piping. I don't see closely spaced tees. How was the prior system piped? To my knowledge, all "Low Mass Boiler" manufacturers strongly recommend either closely spaced tees or the use of a low loss header to avoid the oxygen problem.

joeinmo

One other point is that very little oxygen passes through non-barrier pex until the water gets above 140 degrees, then oxygen entry increases. The lower the water temp., the less the oxygen that enters. Perhaps you're running the water hotter than before your redo? Most likely a combination of factors outlined.

DaveB1972

Agree totally about the O2 infiltration. 

Replace all sources of O2 ingress or remove all Fe components.  

Corrosion lab tech by day (nuclear stainless work) and HVAC tech by night!

farmerzeek

I have an outdoor boiler, a Hardy H4, and it is an open system. I assume that no matter what I do I cannot stop oxygem from getting in? I am in the process of installng radiant floor and will use Pex-AL-Pex just in case I got to a propane mod-con in the future. But as far as I know there is no reason run o2 barrier in an open system like mine. Thoughts?

GGross

farmerzeek said:

I have an outdoor boiler, a Hardy H4, and it is an open system. I assume that no matter what I do I cannot stop oxygem from getting in? I am in the process of installng radiant floor and will use Pex-AL-Pex just in case I got to a propane mod-con in the future. But as far as I know there is no reason run o2 barrier in an open system like mine. Thoughts?

Sometimes you would have a heat exchanger separating your heat source from the heat emitters, in that case o2 barrier tubing would make a lot of sense. or as you mentioned making plans for the future. So yes in my opinion it always makes sense when burying tubing in concrete and creating a permanent fixture, to do things the best way the first time, because you only get one chance to do it right.

farmerzeek

I am not sure what you mean by separating heat source from the heat emitters....I do have a water-to-air exchanger right now in the furnace, but we are hoping to get rid of the forced air so we would no longer use that water-to-air exchanger.The radiant floor is a retro install on hardwood from the basement.

JackW

@joeinmo, I keep the temperature at 130 degrees. Didn't know that, thanks for the info.

JackW

@JAdams, look at the tee above the return line circulator and the input line with the gauge on it. As I understand it, those two tees are spaced at the proper distance apart from each other. I appreciate your input.

JackW

@DaveB1972. I didn't realize the two circs off from my old system were brass, so I'm reinstalling them; Since they've been discontinued, I'll need to find a match of the other two online. Let me ask you this; the old circs don't come with check valves. Do I need to install check valves below the circs on all three lines, or do I not need them at all. Appreciate your input.

JAdams

JackW said:

@JAdams, look at the tee above the return line circulator and the input line with the gauge on it. As I understand it, those two tees are spaced at the proper distance apart from each other. I appreciate your input.

Jack, I'm talking all tees, not just the boiler feed and supply. I think one of the reasons you're having this problem now is the back that you went from a high mass (30 gal.) to a low mass (1.whatever gal.) heating appliance. You didn't have this problem before you re-did the system, did you also change the tubing in the floor? Also, your air separator should be located where the water is the hottest, preferably on the supply pipe coming from the boiler.

Canucker

JAdams said:

Another thing to look at is the piping. I don't see closely spaced tees. How was the prior system piped? To my knowledge, all "Low Mass Boiler" manufacturers strongly recommend either closely spaced tees or the use of a low loss header to avoid the oxygen problem.

I'm confused as to how the closely spaced tees used for hydraulic separation affect o2 ingress from the piping?

EdTheHeaterMan

I had the same problem. There was a company called InFloor radiant heating that sold a system that used a grey PEX tube with no o2 barrier. All the metal components (boiler, pumps, fittings) were made of non ferrous metal. Unaware of this my customer wanted a new boiler and I installed a cast iron boiler and was very proud of the job. After 1 year, I returned for maintenance and noticed the water was very red. But everything was still working so I moved on. In the second season of operation, the customer started experiencing cold areas in the home. I was surprised to find that red mud was everywhere. After several hours of purging all that mud out of each radiant loop, to get the heat operating, I called InFloor to find that the tubing was NOT O2 barrier tubing. Now I had a problem that I needed to resolve.

I came up with an interesting solution. At the time Weil McLain was offering a swimming pool heat exchanger that was made of non-ferris metal. I repiped the boiler room to the pool heater and connected the radiant to the other side of the pool heater. I chose this option because the large "Glumps" of red mud would pass thru that HX while a braised plate HX had smaller passageways and may clog easier. After several flushes on both sides of the system, and adding some cleaning chemicals to both sides of the HX everything was just fine. The system is still operational 20 years after learning from that mistake. Also my customer appreciated all my additional work at no cost to him, so he paid cost for all the added parts. I think he is still a customer of the firm that purchased my company. Finding an error after the 1 year warranty was up was a clear Get Out of Jail Free card, but I didn't want to go that route. I will stand behind the work and my customers appreciated me for that.

@JackW, You may just need to replace any iron pumps and fittings to get your system to operate rust free. I think most ModCon boilers have non-ferrous guts. You may get lucky that way.


Mr. ED

EdTheHeaterMan

@JackW, It Looks like only 3 pumps and 1 tank may need to be replaced. Don't forget the circulator flanges. Use the bronze or stainless steel version of those pumps and use the expansion tank for a heat heater. Those tanks are coated for open system operation. Just remember to adjust the air pressure down to your system pressure (like 12 PSI) or what ever your fill valve pressure is set to.

EDIT: There are some unions at the bottom of the boiler. See if they are ferrous, or non-ferrous metal.


Hopefully the boiler has all non-Ferrous metal parts.

JackW

@JAdams, thanks for your input. Keep in mind that I've had the system running since 2019 with the cast iron circs with no problems with rust until last winter. I've read that it is more than likely the pex that caused the problem, and since it's encased in concrete, replacing the pex is not an option. As far as my tees go, according to Dan Holohan's book, "Pumping Away," pg 86, the tees should never be more than a foot apart; six inches between them is ideal. The tee separating the supply from the return is 5 inches. As far as the air separator goes, if you look closely, you'll see that it's on the supply side; it's a little confusing since the return runs behind it.

Regards,

Jack

JackW

@EdTheHeaterMan. I'm going to replace the cast iron circulators with the two older circs that I originally started with, not realizing they were brass, dummy me. I'll have to find a matching one for the return side. So the inside of the pressure tank is rust-producing, and if so, replace it with one attached to a home water heater? The unions below the boiler are typical dialectic connectors; I'll be sure and check them out; good call; I would never have thought about them. I never thought about the boiler either; that's all I need. I'll check it out also. Thanks for your help, all good stuff.

JackW

@EdTheHeaterMan. The expansion tank I have has a bladder inside of it. I took it off today and dumped what water was inside it, and it came out clear, with no rust.

hot_rod

On the 2 port manifold you might get away with a Grundfos 15-29 those are about the lowest cost stainless I have seen online
The ones Ed showed are union body, so you would need the 1/2 union kits to install them

The flanges, ideally, should be brass also, so maybe a union pump would work out less $$

JackW

@hot_rod. Thanks; if I can't find anything used, I'll have to go with one of those; they're cheaper than the new brass. My two older brass pumps don't have flanges; in a way, that is a good thing. I just soldered the corresponding end to match the shut-off at the top and a union on the bottom side. Thanks for all your help.