Bad day at chez nofossil

Woke up this morning with a flood in the garage - ice dam in the driveway, frozen culvert. Big pain, but I can deal with it.

Then, noticed a couple of odd things. I could hear water circulating in the baseboards. That's not right....

Checked system. Built a nice fire last night, so we should have plenty of heat in storage so that we can skip a fire today. Storage is less than half what it should be. Not good.

Looked at system pressure. It's a bit under 10psi. That's low. I turned off the makeup water valve and the pressure dropped to zero. Definitely not good. Has to be a pretty good leak somewhere. I make a quick tour of the house and basement - no water anywhere in the house. Where the heck could it have gone?

Must be that the HX in storage let go. That's outside, so any overflow would run out the bottom of the storage enclosure and onto the ground. I check the sightglass - storage water level is 3/4" from top, just where it should be.

I close off both ends of all the zones and pressurize the system - pressure holds. Boilers are OK.

With the supply side of each zone closed, I open the return end of one zone at a time and listen for water. The hot tub zone is the culprit. The hot tub is currently drained due to a leak, so that zone hasn't been used in months. I go out and open the hot tub cover. There's my missing boiler water. The hot tub is full and right at 103 degrees. We decided not to use it, though ;-)

Apparently the coil in the hot tub HX sprung a leak, and 550 gallons of makeup water (at 55 degrees) got heated on their way through the storage HX and ended up in the hot tub.

avc8130 said:

EWW.

Think it froze since it wasn't being used?

ac

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No, the HX is indoors and it's been pretty warm here the last couple of days. I think that the hot tub chemicals just ate away enough copper to make it fail. I've had the hot tub HX for more than 10 years. I'll do a post-mortem soon.

On the bright side, the water in my boiler is clean and fresh!

Did some investigation. Here's data from last night. Look at the zone return temperature (should be 15-20 degrees less than supply temp) and see if you can guess when the hot tub HX let go, and when I discovered the problem.

velvetfoot said:

Can you set alarms with that thing?

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Yes - it does audible alarms and email alerts. In this case I didn't have any rules looking for the situation that happened. I could in the future, but of course if I make the effort that particular problem will never happen again. More likely I'll add water sensors on the floor in key locations.

I did the copper as an experiment. It looked pretty solid last time I checked. The post-mortem will be interesting. I'll probably replace it with a small SS flat plate HX.

I feel incredibly lucky that I lost 550 gallons of nasty boiler water into the ONLY possible container that could have held it without making a mess. If the hot tub had been in use, we'd have had that water all over the floor.

Boiler Man - I had a problem with the hot tub portion of the HX plumbing a couple years ago. There's a thread here with pictures. At that time the copper for the boiler portion was fine. I'm thinking that it sat for several months with air and stagnant hot tub water in the bottom this time - maybe that ate the copper.

Maple - the low pressure in my system apparently allowed it to draw in some air, probably through top floor air vents. With air bubbles, I could hear the water circulating. Normally it's silent.

Vizsla said:

Looks like some strong Tea or very weak coffee. Actually pretty good condition and clarity for 10 year old water, even if most is make up. Talk about a best case scenario for a leak

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I have a propane on-demand heater in the system, so I have a filter on the inlet to prevent HX clogs. That probably contributes to relative clarity. Also, I don't know how many gallons my system holds, but it's WAY less than 550. Therefore, the water in the hot tub is something like all 50 gallons of boiler water diluted with 500 gallons of sparkling clear well water,

Bad Wolf said:

Hmmm.. I'm going to have to keep an eye on my system. I stole your design shamelessly for my hot tub and its been working fine so far. Its been in operation for about 4 years so far. Of course mines still running and I think I'd notice water pouring out of the tub and accross the deck.
Was yours a clorine base chemistry or bromine? Don't know if it make a differenance.

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Mine was bromine. It ate the inside of copper fittings that were fillled with hot tub water. As of two years ago, the copper that carried the boiler water looked perfect - some green surface scale, but no pitting or corrosion.