Bad day at chez nofossil

[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]

EWW.

Think it froze since it wasn't being used?

ac

 

[webbie]

Uhhh........some ironized hot tub water!

 

[Nofossil]

EWW.

Think it froze since it wasn't being used?

ac

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!

 

[Nofossil]

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]

Can you set alarms with that thing?

 

[avc8130]

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!

I guess this is why HX designed for pools/tubs are usually SS.

Yeah, the boiler has clean water...and the hot tub looks like a pond in NJ .

ac

 

[JP11]

at least it leaked into a vessel. better to have water somewhere it's controlled than ruining sheetrock and insulation in the house.

 

[Nofossil]

Can you set alarms with that thing?

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.

 

[BoilerMan]

Was it a copper shell&tube or one of those small-looking indirect copper HXs?

I'm anxiously awaiting autopsy pics.......

TS

 

[maple1]

Just wondering what the connection is to the water running through the baseboards?

 

[BoilerMan]

Just wondering what the connection is to the water running through the baseboards?

I'd be willing to wager that the makeup water's dissolved oxygen was coming out of solution, therefore the trickeling noise in the BB.

TS

 

[Nofossil]

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.

 

[Clarkbug]

Glad to hear that at least if it was a problem, it was a contained problem for you. Good excuse to clean the hot tub I suppose....

 

[Vizsla]

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

 

[Nofossil]

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

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]

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.

 

[Nofossil]

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.

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.

 

[DaveBP]

I think I remember that flat-plate heat exchangers are commonly brazed together with a copper alloy. Some manufacturers offer an optional nickel alloy brazing for chlorine exposure. I took that to mean swimming pools but hot tubs would probably fall into the same category.

My well water is acidic enough to gradually eat pin holes in copper pipes after 10-20 years. Had to solder patch several over the years. I don't know if it eats the copper or eats away at small impurities in the pipe that would otherwise be undetectable. It's always been micro leaks that I tolerate for a year or so until they start to drip on the floor.