An apartment water meter has been running high for the last three months for no apparent reason. It's now about 3,000 gallons higher than normal. The meter registers slow continuous usage – even though no fixtures or appliances are active. There are no signs of water leaking into the walls or floors.
Two professional plumbers have checked for problems with no success. We double checked toilets – the usual suspects – but one plumber determined that shutting off the HW feed to the HW Heater stops the meter. So I believe it's in the HW side of the apartment.
The only HW fixtures are only a couple of sinks, a shower, a dishwasher, and a clothes washer. All look fine.
The obvious candidate would be the HW Heater excess Temperature and Pressure safety valve – the "T&P" valve. But the outflow tube from that valve is bone dry.
One plumber suspects the meter. Could a water meter malfunction behave differently depending on whether the valve to the HW Heater is open or closed?
I'm starting to wonder if some fool connected the ice maker to the HW line. What could it be? Any suggestions to isolate the culprit?
Best Answer
Finally resolved this one. It surprised everyone. The apartment had a HW Expansion Tank (required by code) but no check valve (the building has one, but individual units don't).
It turns out water was flowing through the meter into the HW expansion tank, then flowing back out - no net water consumption, just a few ounces of water cycling into and out of the expansion tank with changes in pressure. 3,000 gallons a month is about 9 ounces a minute.
But the water meter only advances in one direction, so it accumulated as usage. We installed a check valve and the problem was corrected.
Wow.