We have a relatively new house (8 years) but an increasing problem with toilets either flushing or running more water into the tank when certain sink or tub water taps are opened.

This will occasionally occur spontaneously without any taps being opened but is more common when opening taps that are not used often.

Whether it has any impact or not the water pipes in the house are all flexible plastic rather than copper.

This is obviously not a critical issue but more of an annoyance!

I actually can't answer your question... but I'm having the same problem myself! Anybody have a recommendation?

I've been told by a few different people that it sounds like there might be a slow leak somewhere... but everyone is currently arguing on WHERE that leak might be...

Two tests to eliminate problem with toilet.

First test

Shut off water feeding toilet.

Mark elevation of water in tank.

Check tank after about 3hrs.

If water is lower, the flapper is not sealing and has to be replaced.

2nd test

With water off drain tank.

Raise float to keep water from feeding into tank.

Mark height of water and with float still raised turn on angle valve.

If water height rises, the flowmaster/ballcock is bad and needs replacing.

Is the feed tube installed in over flow pipe?

Is the water level 1/2'' below top of over flow tube when tank is full?

Let us know if this helps. If not we can go from there.

Good luck

Chuck