Excess corrosion in recently new hydronic system

dave123

System turned of for first time about 2 years ago. Everything new. Weil Mclain SS boiler, 27 gallon buffer, indirect water heater. Nearly all copper piping, with a few black iron fittings and nipples, and short runs of Hepex, no other pex. Flushed with Sentinel's new system cleaner. Filled with city water, which met the listed water requirements for the boiler and the tanks, and correct amount of X100 added per WM's requirements.

Make up water is piped but always turned off, since system was initially filled. System has never lost any pressure or had a leak. Spirovent air separator piped in at boiler outflow.

Now 2 years later, the Amtrol exp tank has two pinhole leaks in it. System fluid has a cola color, and I'm getting flaky, rusty sediment from the dirt separator.

Sent a fluid sample to Rhomar. They show pH 7.66, conductivity 6180 microS/cm, Total hardness 22 ppm, chlorides 30 ppm, sulfates 79 ppm, aluminum 2.5 ppm, copper 0.06 ppm, iron 213 ppm.

Am I right in thinking the corrosion of iron is the main problem? If so, how can this be possible with the system never leaking or taking on make up water, with no clear way for oxygen to get in?

Thanks.

katzaw

Any chance there is Watts ONIX tubing? That's what caused our issue, Oxygen-Diffusion Corrosion
This link from Dan Holohan, (published in 2014!) further illuminates the problem:
https://heatinghelp.com/systems-help-center/oxygen-diffusion-corrosion-in-radiant-heating-systems

My replacement resolution is posted on this site as;
https://forum.heatinghelp.com/messages/6356#Message_35860

Derheatmeister

dave123 said:

System turned of for first time about 2 years ago. Everything new. Weil Mclain SS boiler, 27 gallon buffer, indirect water heater. Nearly all copper piping, with a few black iron fittings and nipples, and short runs of Hepex, no other pex. Flushed with Sentinel's new system cleaner. Filled with city water, which met the listed water requirements for the boiler and the tanks, and correct amount of X100 added per WM's requirements.

Make up water is piped but always turned off, since system was initially filled. System has never lost any pressure or had a leak. Spirovent air separator piped in at boiler outflow.

Now 2 years later, the Amtrol exp tank has two pinhole leaks in it. System fluid has a cola color, and I'm getting flaky, rusty sediment from the dirt separator.

Sent a fluid sample to Rhomar. They show pH 7.66, conductivity 6180 microS/cm, Total hardness 22 ppm, chlorides 30 ppm, sulfates 79 ppm, aluminum 2.5 ppm, copper 0.06 ppm, iron 213 ppm.

Am I right in thinking the corrosion of iron is the main problem? If so, how can this be possible with the system never leaking or taking on make up water, with no clear way for oxygen to get in?

Thanks.

IMO the PH is to low( 8.2 to 9.3 for copper based systems),the EC is way to high (>100 EC) depending on O2 migration the Hardness should also be lower... Aluminium,Copper and Iron are present due to the system fluid Issues.

If you are just using water check the VDI 2035 or the ANSI H1001.1 for more information.

kcopp

Tell us more about the system...
What do you have for radiation?
What temperature is the system running at? (higher temps will suck in more O2)
Inhibitors tend to leave a funky color...BTW you can put in too much. Regardless of what the Mfg say)
I am leaning towards less on the inhibitor side and more on the good fill water side. Axiom makes a really good fill filter... this is what @Derheatmeister is referring to.

dave123

Regarding the Pex--it was sold as, and labelled as, HePex from Wirsbo. About 75 feet total, in either 1/2 or 3/4 inch. There's no other pex in the system.

Regarding the pH, I guess it depends on what reference is used. Romar listed the lower limit of normal as 7.5, but I don't know if a borderline pH could lead to this degree of corrosion.

The distribution is all panel rads, all oversized to run lower temps, so the typical range for boiler output has been 110-130.

Apparently the Fe of 213 is pretty high for a new-ish system. Could there be some other form of corrosion independent of oxygen?

hot_rod

When you add inhibitors it does change the chemistry of the fluid. Did you use a Sentinel test kit or see what there spec shows with the X 100 blended? The test kit should indicate the strength of the inhibitor.

Different chemical company use different blends, so it is best to use their test kit.

Regardless, there should not be sludge colored fluid perhaps, but not deposits.

Does the drain particles stick to a magnet? If so the ferrous metals are breaking down.

dave123

The sediment is a fine grit in mostly shades of brown, with a trace amount of black. Most of the sediment does stick to a magnet.

I dosed the x100 2 years ago by system size per Sentinel recs, namely 1% of system volume. Then did the tablet test, and found it was low in inhibitor, and needed another whole quart. The Rhomar test included inhibitors, which showed molybdenum 294 ppm (which apparently is high), phosphorus 682 ppm (which Rhomar says is a little low), azole 77 ppm, nitrite 17 ppm.

So assuming x100 supplied the molybdenum, the system if anything was high in inhibitor.

hot_rod

It takes a source of O2 to breakdown ferrous metals.

One of the ingredients in hydronic conditioners is a O2 scavenger, that is what needs an occasional boost. I thought sulfites were the O2 scavenger component.

I know the outdoor wood furnaces get a dose of O 2 scavenger on a regular basis, since they are open to atmosphere.

Did the Rhomar test prescribe a way to get the numbers back in line? Can a Rhomar boost be added to Sentential? I didn’t think Rhomar used moly’s.

mattmia2

Did you run the system to drive the oxygen out of the fresh water after you filled it and let it sit?

dave123

As an alternative type of corrosion, I was thinking maybe some odd type of galvanic corrosion, and I thought this didn't require oxygen, but I'm not sure.

Romar's only suggestion was to drain the system, clean with hydro-solv, fill with clean water and then add either pro-tek 922 or x100. But without changing anything else, I'd expect to be in the same place 2 years from now.

Shouldn't the spirovent at the boiler outflow be enough to remove any excessive oxygen?

mattmia2

Was the system run a while after it was filled? If it ran a while the air dissolved in the water and oxygen it contained would mostly find itself to the microbubble separator. If the water wasn't heated after the system was filled then the air wouldn't be driven out, the heat is needed to reduce the solubility of the air in water. It isn't clear from your description if the system was in use and then not for a while or if it was never used after it was filled.

dave123

mattmia2 said:

Did you run the system to drive the oxygen out of the fresh water after you filled it and let it sit?

Do you mean when the system was first filled and the X100 added, did I circulate it? I know I did, though not sure now how long I ran it. I went around opening and closing valves to maximize the flow through different pipes. I know it ran for at least a few hours, because now and then the spirovent would let off a little hiss. It was November, and less than a week later, the system started to be used for heating.

Are you thinking this corrosion could all just be left over from when the system was new? That possibly either the x100 didn't circulate fully, or the system didn't have time to cycle out all the micro-air?

mattmia2

You should have let it heat for a while when you first filled it, not just circulate cold but I don't think that is your problem. Maybe stray current with the chemicals? Other salts besides oxides of iron are soluble.

Derheatmeister

Can you send some pictures of the install..Boiler/Buffer/circs/piping techniques/Panel rads..Is the system operating on a deep setback ?

kcopp

Did you flush out all the cleaner when you added the inhibitor? Wondering about a chemical reaction...

dave123

kcopp said:

Did you flush out all the cleaner when you added the inhibitor? Wondering about a chemical reaction...

I drained the system of the x300 mix, then ran water till it was clear, but I suppose some of the x300 could have been left behind. The total system volume though is about 55 gallons, because of the buffer tank, so I would think that would dilute out whatever residual x300 could have been left after draining?

HomerJSmith

Sys pics would be helpful.

Derheatmeister

Is this Stainless Steel WM boiler oversized..Or does it not modulate..

hot_rod

If the cause of the corrosion is oxygen, either it was not all removed, or somehow oxygen continues to get in

Taking the boiler to 180 or so for an hour will drive out oxygen. The higher the temperature the better air comes out, and O2 along with it

Remaining O2 should get consumed in the oxidation process.

Air getting sucked in a misplaced air vent?

dave123

hot_rod said:

If the cause of the corrosion is oxygen, either it was not all removed, or somehow oxygen continues to get in

Taking the boiler to 180 or so for an hour will drive out oxygen. The higher the temperature the better air comes out, and O2 along with it

Remaining O2 should get consumed in the oxidation process.

Air getting sucked in a misplaced air vent?

Besides the spirovent, the only other air vent is a Minical on top of the buffer tank. I modelled the system after this diagram from a Siegenthaler article called "Simple Yet Elegant Hydronic Systems."



The only differences are that I used a 2 pipe config for the buffer, instead of 4-pipe, and that the circ for the indirect tank pumps toward the indirect, on the hot side, rather than toward the boiler, on the return side; this was Weil-Mclain's recommended config.

But I don't see a way that the vent on top of the buffer could ever be sub-atmospheric. The system static pressure is 12-13 psi.

kcopp

I will say that trying to flush out panel rads is a bit of a challenge. Unless you have the individual rad isolated and flush out the through a boiler drain its not getting all of the original stuff out.
Good news is you caught it now...hope it not lost.
Power Flush out the whole system and use DI water to fill.

dave123

kcopp said:

I will say that trying to flush out panel rads is a bit of a challenge. Unless you have the individual rad isolated and flush out the through a boiler drain its not getting all of the original stuff out.
Good news is you caught it now...hope it not lost.
Power Flush out the whole system and use DI water to fill.

I'm still wondering about an oxygen problem though. Has anyone ever heard of an air vent like a spirovent going bad? How would you know if it weren't working properly, other than unexpected corrosion?

hot_rod

What type of buffer tank? Does it have anode rods in it?

dave123

hot_rod said:

What type of buffer tank? Does it have anode rods in it?

It's a Lochinvar Squire stainless steel tank. No anode rod visible on top of tank, and no mention of it in the manual that came with it.

Derheatmeister

City water report and System pictures would be nice in order to get the full story
Is this system operated on a deep setback during unoccupied times?

Teemok

Was this a soldered copper pipe system? Flux is nasty stuff. I've seen some cavemen over do it inside and out and not hot flush or neutralized the system water after. Maybe the PH numbers you are seeing are the remnants of a very acidic start?

Teemok

Large panel radiators with big air pockets left in them might be an oxygen source for that much iron oxide. Were they individually purged at the high point vents after the final fill?

dave123

Teemok said:

Was this a soldered copper pipe system? Flux is nasty stuff. I've seen some cavemen over do it inside and out and not hot flush or neutralized the system water after. Maybe the PH numbers you are seeing are the remnants of a very acidic start?

Yes, most of the distribution is soldered copper, the rest is hepex. But I did flush with X300 before the final fill.

dave123

Teemok said:

Large panel radiators with big air pockets left in them might be an oxygen source for that much iron oxide. Were they individually purged at the high point vents after the final fill?

I was careful to purge the 12 panel rads after final fill, then again last year, though only fluid came out last time. I have a thermal camera that works well at showing any air at the tops of the rads, and I used this as well.

In retrospect, I probably didn't run the system hot enough or long enough after the final fill, and since then, the system has typically run just in the 100-125 range, which might not be hot enough to drive all the air out of solution. So maybe normal ongoing air entry has also contributed.

I flushed out all the cola-colored fluid and refilled, adding X400, which I'll run for several days. I sent a sample of my city water to Rhomar, they show the water to be acceptable except for a slight elevation of chloride and sulfate, so they recommend a 50/50 mix of city water and distilled, which I will do. But I don't think the initial fill water was the problem here. I think the problem, as some here have suggested, was not trying hard enough to get all the oxygen out, and keep it out. I guess I assumed (wrongly) that the spirovent would take care of it.

Teemok

Cola colored water, I'd be less worried about. Blackish is fairly normal for iron based components. Anything between black and clear but orange, yellow, reddish iron oxide is bad.

I've seen a few systems that had sections of the system tubing done with non-barrier pex. When the installer was questioned about type of tubing used, they responded: "of course I used barrier tubing, what do you think, I'm stupid? They point to the well marked barrier pex you can see in the boiler room. After much investigating due to recurring heavily rust contaminated water and dead pumps the cause is found to be a non barrier tube slip up after all.

It sounds like you are on it with your procedures and testing. Flux or other crap from start up can enter the expansion tank and is hard to get out with normal system purging. Lots of guys run slightly higher system water pressures than 12 psi and don't check or alter the expansion tank bladder pressure to slightly exceed the water pressure. This means the air bladder is always a little displaced by water pressure. There's always some water in the tank vs it only taking on water when the system is hot and then pushing it out when it cools. The tank might have got some crap in it and with low operation temps (low pressure change cycles) and or no use, the crap stays in there being corrosive. idk, grasping at straws.
I worked for a company that loved Silver King #5. The milky water color is a good base that lets you spot changes easily. If I return to my old jobs and the water is clear, I know there's a problem or some, ignorant at best sales type guy as insisted they needed a $600 annual system flush, to keep things working well.