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.

Larry Weingarten

Hi, Another way to check this is to shut off water to one toilet and see in the morning if the leak went away. Try it with a different toilet the following night. With some luck you'll now know where the problem is, and from there can focus on just one appliance.

Yours, Larry

rossn

Thanks, Larry.

Last night I did shut off both toilets. I got the 10:30 alert with those off, as well as the hot branch for the showers and tub. I then turned off the west end of the house, the boiler supply, and the other pex manifold DHW supply lines, and didn't get a second alert, which had happened the 3 prior nights. If tonight runs clear, I'll enable those one at a time until we get there :)

JimBerreth

Is the boiler relief valve or the backflow preventer piped to a drain? One of these could be discharging water during a boiler run cycle and the evidence (water) is going down the drain so you would not see it.

Mark Eatherton

I love a mystery… Who dunnit? As one who has been chasing leaks for over 50 years, I can tell you one thing all leaks have in common. They waste water.

You are on the right track by eliminating potential sources, but I have to caution you that you might have more than one leak, but you're on the right track.

As others have noted, it could be a relief valve (T&P or P only) whose termination is in or near the floor drain. Is there standing water in the floor drain that you didn't put in there? The trap seals on most of the floor drains I've seen evaporate, but I'm on the edge of the desrt (Colorado).Easy way to determine that is to place a cup or vessel of some sort at the end of the relief waste. It's caled a "witness cup". If you find water in the cup in the morning, you've found your leak. Now figuring out WHY the relief valve is doing it's job is your next task.

If the leak is in the heating system, like buried lines between basement baseboard sections, then it may require equipment that you don't have, like infrared cameras, hydrophones or helium injection/detection equipment. Generally speaking tho, a leak beneath the floor would be constant and consistent, and your provided charts don't indicate that.

Another possible issue may be that it's not actually a leak at all, but instead thermal expasion creating NEW water volume that is backing through the flow sensor. If there is a backflow preventer in the incoming cold water line, then the chances of that are slim to none. Go back to the witness cups and see if there is discharge occuring when you're not looking. And it might be the T&P relief valve. During the day, there may be enough water use to keep the pressure low in the DHW tank so the relief valve doesn't actuate when you are looking, but at night, when no use is occurring, the tank has to recover energy loss, and may fire and cause the relief valve to do its thang,

Exess air in the heating system is an indicator of fresh oxygenated water being introduced, but the air can be coming from a WHOLE bunch of other reasons (read Pumping Away).

And yes, potable wate expansion tanks do fail. Biggest problem is incorrect adjustment on new installations. They come precharged, but you must adjust the air charge to the normal operating pressure of your system. And even at that, the diaphragm can fail and cause issues that I've already addressed. I've seen the diaphragms stick to the tank and not allow for any expansion, and tear and fail and on and on.

Keep looking. You'll find it. Good luck and let us know your findings.

ME

Robertw

As Jaimie hall poined out:

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

The refill tube being too far down the over flow will siphon the tank water out and yes likely not be heard or possibly not seen, but maybe a ripple in the bowl. This can be fixed simply by attaching the refill tube to the top of the over flow as indicated in fill valve instructions.

But food coloring in the tank would definitely show if the tank is leaking thru the actuator seal, or if the fill valve itself isnt shutting off completely as they fill the tank from inside the tank, thereby mixing with the tank water

hot_rod

food coloring in the bowl would be an indication of one or both failures. The flapper valve, or the fill tube overflowing or siphoning. It would be easy enough to eliminate one of the variables, to pinpoint the problem.

At some point from a $$ standpoint replace both the fill and flush valve and eliminate both concerns.

GrafHeating

I for one would like to know the resolution on this one. Please report back when it is found.