Intermittent sound of water running through pipe... (tank, color, sink)

[Raquelross]

Since I moved into my new house occasionally I will hear water running through a pipe underneath a specific bathroom sink. I can touch the pipe and feel water running through it. This seems to happen mostly after I flush the toilet and continues even a few minutes after the toilet is filled. Other times it happens just randomly even if I haven't used the water in a while. It only lasts a few minutes, then completely stops. I've thought this could be a water leak but why would the sound occur intermittently and randomly if this was truly a leak? We've also checked the water meter and it doesn't budge after a half hour or so of having the water off. I have also considered that maybe it is water recirculating from the hot water heater downstairs. However, none of the other pipes in the house are making this sound! It is driving me nuts! P.S. Our water pipes run up through the walls; they're not under the concrete.

[Hemlock140]

There are several possibilities, but by the location, I would suggest that the flapper/ball in that nearby toilet is leaking. The tank fills and water shuts off after flushing, but then water slowly gets past the valve an eventually the water level drops enough that the float valve opens and the water runs for a few seconds or minute to fill it back up. You can easily test this by adding food coloring to the water in the tank, then see if the color appears in the bowl without anyone having flushed it.

[TheotherMarie]

Ours does that too and it had me baffled.
I was told that it is the A/C unit draining.
Makes sense, as I only hear it during the warmer months.

[thecoalman]

In addition to what Hemlock suggested it could be the fill valve, as the water rises in the tank there is a float in there that will rise with the water and shut the valve off when it reaches a certain height. If the valve is not fully seating it will allow a little water to pass and the water level will continue to rise, as it rises further more pressure will be caused by the higher water causing the valve to fully seat.

Take the lid off the tank and flush, when it shuts off the water level should remain the same. If the water level continues to rise it's the fill valve.

If it doesn't rise once it is shut off then it's likely what Hemlock posted. Jiggle the flapper a little and see if it stops.

These are fairly easy and cheap DIY fixes. Something like this can easily be costing you more per month in water than what the parts costs.

[QIS]

If the pipe you touch is a hot water pipe then I think you are probably correct about the hot water circulation system being the cause.

[kauailover]

When my fridge is making ice, the ice maker draws water and I sometimes hear the water in the pipes from our bedroom.