Troubleshooting a mystery... leak/flow reported with no physical leak found. Expansion Tank/Indirect

rossn

​Apologies in advance for this being lengthy...

I have an odd situation going on. I have a moen flo smart water valve that has shut off the water after detecting 0.1-0.3 gpm flow for 10 minutes 6 times over the last 3 nights... only late at night. It then turns off the water. I've been up for some to check and turn on the water for half of the events, and then it happens again after I go to bed.

It appears to actually be flowing that amount of water, but to where... it appears to be disappearing? Almost all of my plumbing is exposed, with the downstairs unfinished... no notable leaks found anywhere (a gallon of water would be obvious), no sounds of toilets running, and the only drain connected appliances are a dishwasher and clothes washer + toilets.

I am on a 30 year old natural gas cast-iron boiler with a 20 year old indirect hot water heater. Supply side thermal expansion tank is maybe 6 years old.

I need more active events to test, though it did appear that the flow went to 0 when I turned off the CW supply to the indirect last night, then resumed when I turned the valve back on. On a prior event, I turned off the cutoff valve downstream of the smart meter... when I turned it back on, flow went to 0.

Maybe a year ago, Flo reported a thermal expansion tank issue, but that has not reared its head again until today when I ran maybe 30 Flo leak check cycles, and twice in a row I got that message (when I had turned off the DHW manifold valves off).

Since Sep 28, I have been getting drip reports from the meter. Based on today's testing... think it's somewhere on the hot water side of things.

The other notable issue is that the boiler system has been getting notable air in it for the last year and a half... I have not been able to track that one down.

Is there any possibility of a failure on the indirect that is feeding the water over to the boiler (or a bladder failure)? I would think I would see abnormal pressures there, if that was the case.

Sorry for the ramble... it's complex. Thanks for your thoughts on this one!

Moen Alert Times (shutoff 5 minutes after):

Oct 12, 12:43am 6 mins at 0.3 gpm

Oct 12, 11:25pm 8 mins at 0.6 gpm

Oct 14, 1:51am 5 mins at 0.2 gpm

Oct 14, 10:44pm 5 mins at 0.2 gpm

Oct 15, 12:16am 6 mins at 0.2 gpm

Oct 15 1:37am 5 mins at 0.2 gpm

Robertw

Try food coloring in your toilet tanks to make sure they aren't running? Sometimes its so minor you cant hear it.

rossn

Thanks - I will try that tonight. I assume no staining with that. I can usually hear water downstairs through the abs, but am game for trying anything.

Jamie Hall

My bet would be a toilet tank float valve. It won't be the main valve (likely), but either the level in the tank set just a tad too high, and overflowing through the overflow, or more likely the float valve not quite shutting off and discharging through the tube which goes to the overflow. You won't hear that, and you won't see it in the bowl, either.

If it's the bowl recharge line from the float valve, food colouring in the tank won't show you that.

rossn

Thanks, Jamie. I will note and check that. Odd thing is it only happens late at night and wee hours of the morning. Maybe tonight I will just turn off the toilet supply lines. One of those toilets has a toto washlet on it, as well.