Major disaster in the making

[Bad Wolf]

I just found a puddle of water on the floor by my unpressurized storage tank. When I opened the access hatch I could see the tank was overflowing. There is obviously a leak in either the hot water heat exchange coil or in the boiler heat exchange coil.

Here’s the background: The system is two years old, just entering the third heating season. The boiler is a TARM Excel 2000. I made the coils my self out of ¾ inch refrigeration tubing, two coils 150’ each. I saw someone else using that and I knew that heating pipes usually use the thinner wall stuff anyway.

I haven’t located the leak yet. I pumped down the tank 6” and will wait to see how fast it comes up again. I’m thinking it must be a pretty small leak and it didn’t overflow until I fired the boiler Sunday morning started to raise the tank temp. I use the system for my DHW all year long, so I was firing it once every 5 days or so in the summer and increasing to every night the past 3-4 weeks. Of course this couldn’t happen in August.

I think step one will be to call TARM tomorrow and find out how to jumper my controls to run with out storage, I have ball valves on the supply and return to the storage tank so I should be able to cut it out of the system. Step two will be to borrow an electric hot water tank from a friend and bypass the hot water heat exchanger.

Now I will be able to pump down the storage tank and see what is leaking.

I see two possibilities either the pipe itself has developed a pinhole leak or one of my joints is leaking. Now my water is acidic and I have had problems with my domestic pipes leaking but that was after years and never in the heating system even before I switched to wood. I did adjust the ph of the tank when I filled it to about 7.
If it’s in the pipe I can’t see just patching it and waiting for another leak to develop. I hate to redo the coils though, and if I use type K it’s going to run me $1200 for the tubing.

I’ll post updates as I find this out. And of course I’ll use this group as a sounding board and for advice. Thank God for the Hearth board.

 

[DaveBP]

Any way you could valve off and isolate the heat exchanger system in the tank and leave the rest of the boiler operations intact? That way you could put in an air valve (like on a tire) and put compressed air into it. Looking for bubbles in a full tank might be easier than draining the tank and looking for a drip in a soggy environment.

 

[Bad Wolf]

Actually that is a good idea. Yes I have two ball valves the isolate the loop that goes to the storage tank. It might be a little hard to see all of the heat exchanger coils though, I may have to pull the whole cover off anyway. The foam board I used is sagging and the EPDA liner I attached is dropping away from the cover. That would help identify the leak but I'm still left with the fix.

 

[tom in maine]

Hi Greg,
If your water is acidic, I suspect you have a pinhole that formed from the inside of the DHW hx.
We have seen this on occasion here in Maine. There are some areas where the geology makes the ground water go
acidic. When this happens, the copper starts to corrode. It doesn't happen often, but when it does, it is bad.

A permanent fix is to get a water test and treat your water.
Another potential solution is to do a PEX dhw hx. I am not a big fan of the concept, given the cost and other issues, but
it is an option.

I would take out the DHW hx and pressurize it with a hose to check for the leak although as you said, there is the potential
that the copper has been compromised.

 

[Bad Wolf]

Thanks Tom Actually I hope it is the DHW. It would make sense, the boiler only gets charged once, but the DHW sees a constant flow of fresh water. I have a pH adjust system that feeds soda ash solution into the domestic tank every time the pump runs, however I haven't been good about keeping it filled. I have a spare coil in the tank that was intended for a solar colector system that I haven't gotten around to hooking up yet. If it is the DHW I could just switch over to the other coil (with treated water now!!) and fix or install a solar coil next spring. I'll keep my fingers crossed.

 

[Singed Eyebrows]

Hopefully it's just a solder joint leaking. If it did pinhole a patch might last quite awhile. A permanent fix might be stainless tubing of good quality. I know if I had an unpressurized tank I would have cast iron radiators sunk in it, Randy

 

[tedw]

I don't mean to hijack your post but I'm interested in hearing about what you found as I have the same problem. Last night I noticed a puddle of water by my STSS unpressurized storage tank (installed with Tarm Excel). I noticed the water level was high and when I took off the upper panels there was water on the insulation board. So I suspect I have a leak in one of the loops as well. What did you discover and how did you locate the leak?

 

[Bad Wolf]

So far I haven't been able to drain down the tank to find the leak. I've been pumping off excess water every 4 or 5 days. I found an electric water heater for free on Craigs list that I will hook up to bypass my DHW coil. Once I'm set with that I'll jumper the controls and close the valves and run without storage. I can see a couple of spots that look like they have corrosion on the outside of the coils and one spot that looks like the pin hole leaks I'm had in my regular plumbing. I bought some boiler treatment that I will add once I find the leak.

I'll porbabluy have to wait until Christmas break where I have a whole week off

 

[tedw]

Thanks for the quick reply. How are you pumping off the excess water? Do you have the same tank as me -- STSS? I think I may go that route also because I don't have the time to mess with this now.

 

[Bad Wolf]

I just dropped an old sump pump and garden hose in it. I made my tank and coils but stole the design from STSS.

 

[tedw]

Thanks, I just did mine slowly siphoning from a pipe exiting the top. Now that I see how slow the leak is I think I may wait until spring to pull the tank apart.