Corrosion

JAdams

Not sure which category to post this one, but it has to do with corrosion on the fittings of the supply side coming off a cast iron boiler. Water samples have been taken and sent to labs for analysis. There are no results yet, as I just sent them in. There is no antifreeze in the system, although the water in the heating system tested at 5.4 PH. A little acidic, but I don't think it's enough to do the damage it did in less than two years. I have attached a couple of photos of the stainless steel fitting that was screwed into the boiler on the supply side. Below are the details of the system.

The original system was installed in 1997. Buderus G215-5 Boiler. Buderus ST Indirect Fired Water Heater. the entire house is radiant heat with Entran Onix Aluminum O2 Barrier by HeatWay. Originally there was hydronic antifreeze in the system; however, it was all removed and flushed out because of the black iron nipples rotting out on the supply side of the boiler. There was still something going on because the boiler eventually started to leak on one of the lower push nipples and had to be replaced.

A new Buderus G215-5 boiler was installed Feb. 2021 in place of the one that was leaking. The stainless steel supply manifold that comes with the boiler suddenly started to squirt out water. Upon removing the fitting, I saw that the pipe, within the threads, was gone, where it screwed into the cast iron. Note that the corrosion was on the top half of the fitting only. Keep in mind, this is only happening at the boiler, nowhere else in the system. Also, keep in mind that the electrical system is an off-grid system; it is a battery with inverters & generator.

My thought on the cause of this issue is a combination of bad water & electrolysis. However, there may be an O2 problem as well. I did find a ground wire on the copper water pipe, which I recently disconnected.

My question is, has anyone seen this before, and could the Entran Onix tubing be contributing to the problem?

I look forward to any input. Thank You in advance.

hot_rod

Certainly could be a combination of things

low ph is hard in aluminum, the boiler manual should indicate acceptable levels 

Chlorides are tough on stainless, the water assessment will tell as will the tank manual water quality requirements

Dissimilar metals in water with high conductivity, high TDS will dissolve the weaker metal.

There is a track record on non barrier tube allowing excessive O2 into the system. The higher the boiler operating temperature the more O2 ingress

You may have the perfect storm of conditions.


Probably need to flush, run a cleaner, flush again, add DI water. Most likely an ongoing chemical treatment, especially oxygen inhibitors and ph buffers   A yearly if not twice a year test of the water. The inhibitor product you use will have a specific test kit you can use yourself.

JAdams

Thank You, Bob. I'm still waiting to hear back from the lab on the water sample that was sent in.

Derheatmeister

Opions differ on this subject and it can be addressed many different ways....I may be able to give you some advise on a remedy towards this situation. If you wish you can contact me directly

Jamie Hall

You may have a severe electrolysis problem. You mention disconnecting a ground wire -- which may have been a mistake. Since you are off grid, you really don't know (unless you've done careful measurements?) what stray currents you may have. I would suggest that you undertake a comprehensive program of bonding everything metal to everything else metal and to a central, but single point, ground. If you have a storge tank, you may also find that putting sacrificial zinc anodes in it might help (like we do on ships).

Note two things: first, the voltages involved may be very low and almost impossible to measure. Second, do NOT count on metal to metal contact, such as threads in a pipe fitting to make an adequate bond. Tjeu won't, particularly if any pipe dope or teflon tape or anti-seize was used.

JAdams

Here's a copy of the water analysis reports for the Heating System and Domestic Water. Note that the heating system is filled with domestic water.

ethicalpaul

Acid wow

JAdams

Jamie Hall said:

You may have a severe electrolysis problem. You mention disconnecting a ground wire -- which may have been a mistake. Since you are off grid, you really don't know (unless you've done careful measurements?) what stray currents you may have. I would suggest that you undertake a comprehensive program of bonding everything metal to everything else metal and to a central, but single point, ground. If you have a storge tank, you may also find that putting sacrificial zinc anodes in it might help (like we do on ships).

Note two things: first, the voltages involved may be very low and almost impossible to measure. Second, do NOT count on metal to metal contact, such as threads in a pipe fitting to make an adequate bond. Tjeu won't, particularly if any pipe dope or teflon tape or anti-seize was used.

Thank You Jamie, I always appreciate any input that anyone can give. I'm trying to find the reason and a cure for the problem in this system, as I've never seen anything like this before. I disconnected the ground on the water pipe in this house because there is just no need for the interior water piping to be tied to the electrical system in this house. I've done extensive reading on electrolysis, and all of what I've read suggest separating the electrical from the plumbing systems if possible. There is not 8ft or more of copper water tubing in the ground; therefore, grounding the copper water pipe in the house is exempt from the NEC, I do believe. Also, by having the copper water pipe grounded, it may have been transferring low voltage to the water system, which is tied to the heating system, therefore adding to this problem. All I can do is try it and see.

Jamie Hall

What you need to avoid is voltage difference -- even very small ones -- and the current involved finding a way (it will!) to get from point X to point Y. This is why I suggest bonding everything together if at all possible.

Where you can get really severe corrosion problems happening is when the electrical system doesn't have an adequate neutral return path. The stray current will try and find an alternate. The fact that grounding the water pipe in the house is exempt from the NEC is that if you are grid connected and there is a faulty neutral -- or flaky wiring -- the ground can carry quite large currents which are a safety hazard. The NEC, for all its value, doesn't care about electrolytic reactions.

The comment about separating the plumbing from the electrical is somewhat similar -- and again has value: the last thing you want is a pipe with current. However, there are two ways to avoid that: make sure that the pipes are all similar materials (dissimilar materials will create a battery, and unless shorted out with a bond will corrode at the connection point) and carefully insulate them -- or bond them together and then ground them. I personally prefer the latter, if only because that way if there is an accidental connection between something live and a pipe, it will blow a fuse or circuit breaker.

And remember -- even if you are off grid, for safety all your wiring should have a fused or breaker equipped hot feed (or feeds), an unswitched neutral return (not required on some 240 volt applications) -- and an unswitched ground. Don't cheat; stay safe.

ScottSecor

I suspect this is anecdotal, but stainless steel pipe, fittings and circulator bolts don't fare well I'm my area of NJ.  I've seen similar galled threads on ss nipples and fittings.   Spent wat too much time on ss nuts and bolts on small circ pumps with minor flange leaks.  Not sure if it's the boiler water, city water or the hear (180 typically).  I sort of assumed it was due to the dissimilar metals,  but this was never confirmed. 

JAdams

ScottSecor said:

I suspect this is anecdotal, but stainless steel pipe, fittings and circulator bolts don't fare well I'm my area of NJ.  I've seen similar galled threads on ss nipples and fittings.   Spent wat too much time on ss nuts and bolts on small circ pumps with minor flange leaks.  Not sure if it's the boiler water, city water or the hear (180 typically).  I sort of assumed it was due to the dissimilar metals,  but this was never confirmed. 

Thanks for your input Scott.
Now that I have the water sample analysis back on this system, I'm leaning toward a bit of everything; high ph, and electrolysis between the dissimilar metals. It doesn't seem as though the system is getting saturated with oxygen due to the low PH level. I'm just going to flush the system, put some additives in it and maybe refill it with DI/RO water.