Here's my situation. Bought a house in June of last year. House was built in 1992 and built on a somewhat steep hill. The back of the basement is all below grade, and the front is at level grade. All was good until Halloween when the tenant in my basement suite noticed some water pooling in the utility room. Hot water tank checked ok. It's under a year old. A plumber came out and suggested directing drainage away from the side of the house where the downspouts come down. Did that. Tenant moved out, insurance claim was made and they sent a restoration company out. Basement suite has now been stripped to bare concrete and drywall removed two feet from the floor. The floor is generally wet from the center back area in a rough semicircle outwards.
The utility room is about 20 feet from the back wall. Eventually they found an old crack in the back foundation wall that had been repaired some time previously, but the repair has failed. Had a contractor seal the perimeter of the base of the wall with Xypex. The next day, the floor was still wet so more Xypex was applied a little further up the wall. Checked again a day later and the water was over an inch deep in the same area. Almost as though he had plugged the drain, not the ingress point. I should note that the water appears to be clean, and there is no smell. If I shut the water off to the house then nothing further happens. If I turn it on, then water appears again overnight, but only overnight. If the floor is pumped and dried, it stays dry all day even with the water on. Irrigation has been shut off. Nothing else I can think of uses water automatically overnight. Last night I left the water on, and took water meter recordings. Between going to bed and waking up, the meter recorded about 250 litres (66 gallons) flowing at some point. The only usage I know of was a toilet being flushed once. Water on the basement floor is significantly more spread out this morning. Any suggestions as to what I can try? Restoration has had plumbers and HVAC guys out repeatedly to figure this out, and I feel like I'm still at square one.

Other things that might be red herrings to this, but I feel should be mentioned:
-water hammering in my fridge started about the same time as the water pooling was discovered
-my laundry tub on the same line as the fridge always has murky water when I initially turn it on, both hot and cold
-in the midst of this, the overflow valve on the water heater failed. It leaked water all over and when I shut off water to it overnight until I could address it the next day, water leaked quite rapidly from a main level shower head and a bathroom faucet even though they were both turned off
-replaced the overflow and the hot water was fine, but the pilot kept going out overnight only for about a week afterwards. Would stay on all day but go out overnight.
-irrigation was blown out about two weeks before the water was noticed in the basement
-there is a surprising amount of condensation on the inside of my windows in the upper main part of the house
-immediately above the problem area in the basement is a covered deck. The drop ceiling tiles in the basement have been partially removed, and there is dampness between the underside of the deck and the batt insulation. I've been told that the insulation is incorrect, and I suspect this is a separate issue from the rest as there is no moisture going down the walls or dripping from the ceiling.

It has been four months now and everyone I have working on this is stumped. Any suggestions would be greatly appreciated. Thanks in advance.

Has the water pressure been checked on the incoming supply? If yes, with a lazy hand gauge that would show any overnight pressure spikes? Are there under slab water supply pipes?

I've had the city come out and check my water main and all of the neighbors and they found no issues. Is there something I can do myself? Is it possible that the pressure could spike overnight and cause a temporary leak?

I would check the pressure with a lazy hand gauge and see if the pressure is spiking overnight. Can you monitor any daytime usage on the meter? Are there under slab/ground water supply piping? The gauge screws onto a hose bib(garden or washing machine).

[www.plumbingsupply.com]

Where does the city water line enter your house? From front or from the hill in the rear? Where is the water meter located? Do you have a prv or no?

If you have a cutoff valve in front of your water heater, it would be interesting to shut only that off before bed and see what happens with leak and with meter with the cold water on and the hot water off all night.

Very interesting scenario.

Is there a floor drain in the area where the water pools on the floor? (In other words, are you seeing water at the low point of the basement floor, or is that water originating at the point you see it?)

The house is typically empty during the day as we're all at school or work. I can take a reading off the meter when we leave the house and compare it to what it reads when we return if that would be helpful.

The city water comes in through the side of the house, relatively far from where the water is pooling. The meter is in line at the same place. To my knowledge, there is no pressure relief valve other than the hot water tank.

There is a cutoff at the hot water. I can try that tonight, I haven't done that since the leak on the tank. Do you think this could still be an issue with the hot water?

The low point of the basement is near the hot water tank, and there is a floor drain there. The water generally migrates there eventually but it isn't immediate by any stretch. I would guess settling in the last 27 years has brought the level of the floor slightly out of whack. It seems to pool at the back wall and slowly move its way forward toward the drain.

Make sure your leak is not a toilet flapper leaking by or a faucet leaking or a hose bib that you don't know exists, before you proceed. Your best solution is to re-pipe i.e. replace water lines under the ground or in the slab to rule out a leak. Use code approved piping and install it according to your local Plumbing Code. NO SHORTCUTS. Use a local qualified or CERTIFIED Plumber trained in a school for this job...you will be thankful for hiring knowledgeable craftsmen for your job. Lots of things to consider. Soil type, depth of piping, Water Pressure, etc. Good luck.

Fixed. Turned out to be the prv.



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