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water leaks behind the wall after I flush the toilet and after the tank fills up and stops then I hear drips down in my kitchen. If I turn the water off at the shut off valve and flush afterwards I do not hear the drops in my kitchen. Could it be the shut off valve under the toilet?

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This sounds like the float valve inside the toilet might be allowing the water to drain down the overflow tube. Normally, the float will stop the water before it gets to the top of the overflow, but if the float is leaking or out of adjustment, the water can spill over the top.

When water leaks into the overflow, it goes into the tank, and when it goes into the tank, it fills to the point that water will start to trickle down the drain. When the water trickles down the drain, you may be able to hear it "running" down the sewer pipe in the wall.

Take the lid off the toilet tank and watch what happens after you flush. Any draining issues should be apparent. The same thing can happen if the flapper valve is leaking, but then you normally hear the toilet fill back up a little bit every few minutes.

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I think you're hearing pipe creaking due to thermal expansion. If it was leaking that much you'd know it due to moisture and mold.

Here's what's happening:

  1. You flush the toilet. Cold water flows through the pipes to the tank, contracting the pipe.
  2. Where it makes firm contact with the wall framing it creaks at regular intervals, slowing and then stopping when the temperature stabilizes.
  3. If you close the valve and flush, no water flows through the pipe, so no contraction occurs.

Solutions involve lubrication or relief of pressure on the pipe by removing wood. There are a number of questions on this site with more information.

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