This question needs a bit of background.

I live in a unit that I rent in a building of 8 units. There is a central gas water heater for the whole building. Each unit has it's own separately metered hot water pipe. The meter measures the water that flows through it, and I am billed for gas usage that is calculated from the water usage.

A few months ago, I heard a noise that I thought was just someone else in the building having a shower, but it continued for a long time (and was accompanied by colder water in my shower), and it turned out that my hot water pipe was leaking. Strata management sent a plumber out to repair the pipe.

More recently, I heard the same noise, so I ran out to my meter and noticed that it was measuring a flow, even though nothing in my unit was using any water at the time. I turned the hot water off with the tap that is before the meter, and went out to do some things in town. When I came back, I turned the tap back on to investigate, but the water was no longer flowing (unless of course, I turned on a hot water tap in my unit).

What could cause this recent behaviour? At first glance, it seems like the pipe must have started leaking again, but then stopped without any maintenance being performed (which seems unlikely to me). The only other explanation I can think of is that the pipe for my unit is also connected to some other tap elsewhere in the building, but I wanted to ask on here before going down the route of trying to prove that.

  • 1
    The only other explanation I can think of is that the pipe for my unit is also connected to some other tap elsewhere in the building - that's what I'm thinking. – manassehkatz Nov 14 '18 at 22:22
  • 4
    Turn off your hot water supply at the meter again and wait to see if any of the other residents complain about "their" hot water having mysteriously stopped flowing. – CactusCake Nov 14 '18 at 22:32
  • 6
    Or see if the valve gets turned back on without explanation. For chuckles, put a lockout/tagout on it. – Harper Nov 14 '18 at 22:35
  • A remote possibility is if you have a "anti-scald mixing valve" for your shower that is malfunctioning and when you use cold water somewhere else, it is actually sucking (siphoning) hot water into your cold water pipe. But if the sound happened when no water was flowing anywhere, then I'm with the others, there is a cross-connection to another unit somewhere. – J. Raefield Nov 15 '18 at 1:39

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