Ghost leak - cannot find it!

[plumber_not]

Hi all,

First time poster because this is driving me crazy. I have a leak somewhere, but I cannot find it.

How do I know? I have a smart water valve that alerts of certain flow conditions and my smart water valve has been telling me that I have low-flow leak, everyday, since Oct 2021 (8 months now)! I've done everything I could to try and find it. I do not have a complicated or huge plumbing system.

Here are some facts:

-house was built in Aug 2017 up to date (for Canadian standards)
-I have photos of when the house was being built: all the pipes are in the floors/ceilings, and rarely in the wall, except for the basement washroom, the toilet and sink pipes are in the wall (built-out plumbing wall). why this information is important will come later
-the leak ranges from 0.5 to 0.7L/hr or about 15 to 20L a day
-when I close the main water valve, within 5 to 10 seconds, the smart water valve leak conditions correct itself and says the leak has been resolved (see photo)
-the utility meter, also shows a small leak (small dial turns a bit, every few seconds, see photo)
- I've used the ink in my toilets tank, not leaking toilet
- the smart meter water valve alerts me of low flow condition when water flow is detected for more than 2 hrs, and then it tells me that the condition is resolved if the water stops flowing for more than 5 seconds or so. I get multiple warnings everyday because it flows and then resolves itself repeating this cycle all day long, for 8 months now ..so it doesn’t seem to be a continuous leak, but its present every day, but at times it can go for 16 hrs straight, but never continuous.
- just last week, we went on vacation and turned all the valves off either near/at the receptacle (i.e. vale under the sink or toilet) and at the mechnical room (but I did not turn off the main house valve one), to determine where the leak could be;

1. all 4 toilet cold lines off
2. all 4 bathroom/washroom sinks cold and hot off
3. humidifier
4. washing machine (hot/cold) and dryer steamer lines (cold)
5. outdoor hose bib lines (2 colds) - valves in mechnical room
6. garage sink (1 cold 1 hot line) - valves in mechnical room
7. Kitchen sink off (hot/cold)
8. dishwasher

At this point, the only thing that has water is

-3 showers/bathtubs (which are bone dry)
-fridge water/ice maker
-hot water tank (with recirc pump and line)

With all those valves off, we were away for 7 days and I lost 100L of water

Next, you might think there is a leak somewhere in the pipes/lines. I must say, there is no evidence of water in my walls or ceilings...since October of 2021, I would hope by now, it would show itself, especially considering its around 20L/day, but nothing out of the ordinary in my walls or ceiling.

I even used a thermal camera back in November and December (cranked up the furnace to high temperature) and found no unusual stains or spots in the drywall/ceilings (mind you, I’m not an expert in thermal imaging).

So, now i don't know what else it could be? I suspect the water is going into a drain because I see no evidence of water damage in the walls/ceiling over the last 8 months, but I have no idea now.

I suspected the hot water tank was leaking through the condensation tube, and into the drain. I was thinking of isolating the hot water tank for a bit, to see if the leak stops (I haven't done this yet).

Any help or input would be greatly appreciated. Please let me know if you have any questions about my home, I would be happy to answer them!

 

[Twowaxhack]

You need to determine if the leak is hot or cold.

Turn the cold water valve off to your water heater and verify it works by opening a faucet and that flow completely stops.

Then go look at your water meter for movement.

 

[plumber_not]

thanks @Twowaxhack. Please see photos of my hot water tank and relevent valves with letters.

Just to be clear:

1. Do I have to turn of the recirc pump first before I shut cut cold water to the hot wate tank?
2. Do you want me to turn off valve A only in the photo?

Valve B and C are part of the hot water recirculation system, and valve D is the expansion tank valve.

second photo for more clarity.

thanks

 

[Twowaxhack]

Just turn valve A off and do not open any faucet.

Then check your meter for movement.

 

[plumber_not]

Just wanted to provide an update, last night and overnight I turned off Valve A, and I made a mistake not to write down the numbers on my Badger meter...so I'll have to try it again tonight. HOWEVER, it seems to have improved the leak because my smart meter only complained once and resolved itself overnight.

I'll have to try this again tonight to confirm.

thanks for your help so far.

 

[Twowaxhack]

You should only need to watch the minute leak indicator for a few minutes.

 

[plumber_not]

thank you @Twowaxhack I finally had a chance to do this uninteruppted. I conducted a 7.5 minute test with valve A turned off and you can see the water loss during that time.

0.00073 m3 to 0.00079 m3 in 7.5 minutes

thats about 60 mL during that time or if I extrapolate that number to 1 hr, its about 480 mL in 1hr

Does this mean the leak in my cold lines?

 

[Twowaxhack]

Most likely a cold water leak. I would suspect a toilet or a fast dripping faucet.

Check everything and everywhere you can. Check any lines that may go outside.

Do you have water pipes in the concrete ?

 

[plumber_not]

No lines that go outside, the only line that I know of that is in the concrete (basement floor) is the main line (shown in blue in some photos below). Also, I should mention the smart meter has a backflow preventor, so water is not going backwards (if there was a leak in under the concrete).

Most of the lines are in the above floors/ceilings with the exception of a couple of places where the pipe is in the wall to the plumbing receptacle , and our basement bathroom with the plumbing wall (some photos of that).

You'd think after 8 months I would see something.

I'll start with shutting off 1 toilet at a time again, and see if something changes