Indirect Water Heater -Rusty Colored Water - Help me diagnose

HandyFS

I can use some ideas on an indirect water heater I'm working on. Trying to determine if this is sediment, or possibly a break in the indirect water heater coil from the boiler.

Indirect Water Heater/Radiators/Boiler:
Weil Mclain Gold 50 gallon water heater that's connected to a Weil Mclain boiler. This is an older Triangle Tube Weil Mclain Gold, not the newer style. This boiler is heating the indirect water heater, and radiators throughout the house. Water heater looks to be in great shape from the outside, no leaks. For the record, these indirects have no anode rods, and no drain.

Issue:
It sat for a while (Over a year+ with no use). Once we got the boiler back up and running it seems fine, no leaks after reworking the supply inlet, but the water would come out rusty after sitting for more than a few days. I went ahead and took the supply side, removed what was left of the dip tube, and did repeated draining and refilling from the top inlet port with an electric pump. I made a temporary dip tube that connected to a hose end so I could flush the water in with a hose and the water pressure, then used that same setup to drain the tank from the bottom with an electric pump. So it seems like it would be hard to still have sediment in the tank since I did this drain/refill multiple times.

First Gallon to domestic is colored:
If the water heater sits for a few days, the first gallon or so has a slight yellow rust color to it. It still not in full daily use so I'm not sure what happens if its used daily, but I'm trying to get to the bottom of it before its being used daily.

Pipes In/Pipes Out on Domestic:
The water supply line going to the water heater and output to the faucets is all new, so the rust water is either coming from the interior of the holding tank within the water heater, or worse, its somehow water that is coming out of the boiler water that heats the water heater coil.

Pressure:
From what I can tell, the pressure in the boiler is roughly about 12psi when cold. That number doesn't seem to change. I assume IF the coil inside the water heater had a crack, the water pressure in the boiler would be dropping steady. Its been warm so the system hasn't been running all that much, but I think I may plan to force run it and jack up the heat and empty the water heater completely at the faucets a few times strategically over a few days to see what that water pressure does.

Is Coil Cracked? Symptoms?:
If the coil was cracked inside of the water heater, would this in any way raise the pressure in the boiler? Or does it nearly every time drop the pressure as the water leaks from the boiler loop through the coil and into the domestic hold tank? I'm assuming the boiler pressure would always drop.

What to try next?
Can there STILL be rust/sediment inside that's causing this? I flushed this thing multiple times, and drained it from the very bottom. Maybe I need to pull the relieve valve and try to run water in the inlet and let it flow out of the top instead to see if that helps clear up any possible sediment/surface rust that may be on the upper components in the tank?

I called Triangle Tube and the support rep told me that its common for these water heaters to run cloudy for a while if they sit for a while, but that eventually it should clear. I was told the coils on these barely ever fail, but that the main problem is typically the holding tank gives out and the leak is visible. So chances of the coil being cracked are low I suppose, but I'm not ruling that out since I've flushed this thing so many times.

Looking for some last ideas to try before I cut this darn thing out and replace it.

Thanks for everyone's time and knowledge. You've all helped me through some tough things, and I appreciate you all and this community greatly.

mattmia2

If the coil is leaking the pressure in the boiler will rise because the pressure on the DHW side is higher than the pressure in the boiler.

What kind of fittings are connecting to the indirect on the potable side? Galvanized fittings like those in dielectric unions tend to rust and leave a slug of rusty water.

I think the only way you would be able to get the sediment out would be with some wanding and sucking the debris out with a tube to the bottom and possibly some acid or possibly inverting the tank and wanding. It might be better left to someone that specializes in tank cleaning.

SuperTech

My first thought is to check all the piping and fittings. Is everything copper, brass or pex? Any ferrous fittings or pipe anywhere?

The pressure relief valve on the boiler would open or drip if the coil was no good. I wouldn't worry about the boiler side of things. Your culprit is on the domestic side of the system, in the plumbing or the tank itself.

HandyFS

https://forum.heatinghelp.com/discussion/comment/1811965#Comment_1811965

Thanks for that info. Makes sense. Boiler at 12PSI, water pressure is at least around 50-60PSI. The pressure is definitely not rising in the boiler so maybe its not the coil if a sure way to know if a coil has issues is pressure going up in the boiler.

For fittings, I had to adapt a coupling style adapter on the water inlet side so that's new other than the existing stainless nipple going in. On the output on the domestic side, almost sure its a normal union that goes directly to copper, I'll have to double check this since I do think it may be a galvanized union.

For cleaning, I injected water at the bottom inside the tank using a piece of 1/2 PEX adapted to a garden hose, so I got it down to the very bottom and all around. Same with pumping the water out, I was able to pump almost all the water from the bottom. I didn't try any type of long pipe brush or anything though, seems like that would be pretty difficult, but may be worth a try.

https://forum.heatinghelp.com/discussion/comment/1811969#Comment_1811969

There is a union between the stainless domestic output nipple, and the copper up above. That's the only thing left since I changed the union on the cold water inlet side, and everything else is new copper and pex. At this point it may be worth just taking that off and having a look since I've done just about everything else. The water only runs yellow for the first bit of water, so that may make sense if the union is possibly causing the water to rust in that spot since its the first water out of the tank. Let me give that a go and if that's it, that would be an easy fix for this particular system that's given me a good run and taught me far too much.

Pressure relief valve on the boiler was changed recently when I started going into this system as a preventative and shows no signs of drippage, and the pressure is definitely not creeping up. I guess I should run a few heating cycles again since its been a while since I last checked, but if I see it creep up at least I know its definitely that.

I think you're right its somewhere on the domestic side. Which leaves it to that hot water nipple union, the tank itself, or the coil surface in the tank.

For whatever reason, this indirect was installed without isolation valves. I'll certainly be installing those if this thing has to come out.

One thought, I haven't touched the pressure relieve valve on the water heater. Any chance something on that is causing it? Almost sure that has a brass body so i'm guessing that's not the case. I may change as a precaution anyhow, but its drain tubes are all sweat on so I didn't have the time to deal with cutting and replacing, but I'll add that to the list.

Time to get that union off, and do some heat cycles to see what the pressure does, and if the water keeps running rusty. I'll keep you all posted.

IF anyone has any other ideas or feedback, I'm all ears and will add it to the list once I get back cracking into this thing in the next few days.

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