A: Since your toilets are fairly new, and the fill valves have recently been replaced, and since both toilets have the same problem, I believe a little human error is to blame with this one.

In most toilets, the fill valve or "ballcock" fills the toilet from two discharges. One opening at the bottom of the ballcock fills the tank, and the little hose at the top fills the overflow tube going down into the bowl to reseal the trap. This little hose needs to be clipped to the rim of the overflow tube as per the manufacturers instructions.

Unfortunately, many people make a common mistake by skipping that step and may simply tuck the hose into the tube -- causing the hose to be too low in the tube. A low hose can actually cause a siphon in some style ballcocks... and there you have it. Water can constantly be siphoned from the tank and will drain into the bowl creating the dreaded "phantom flush."

So, before you replace the toilets, check to make sure the fill hose is clipped properly to the rim of the tube so you don't get your wallet "clipped" with the unnecessary cost of two new toilets!