Thought I would run this by you guys and hear your thoughts on what might be causing an issue we have with our toilet. Recently the fill valve on one of my toilets failed so I replaced it with a fludimaster. The toilet flushes fine but noticed that while flushing there is a strange gurgling sound that comes from the overflow pipe in the tank. I have tried to determine what is causing the noise but I am at a loss. I noticed it does not make the noise until flapper has closed up the hole in the tank and If I take the tube out of the overflow pipe it does not make the gurgling sound.

Another problem I am having with this same toilet is that as soon as the water has finished filling up the toilet tank you can hear a slight thump when the fill valve cuts off the water. I thought it might be water hammer, but it only makes the noise once and we do not get the noise when we shut off the water at other parts of the house including the other toilet. Is it possible that I just purchased a faulty fluidmaster fill valve?

Sounds like excessive water pressure -- Try turning the stop down a bit.

Which stop are you referring to, the main or the one at the toilet? Also, this did not start until I replaced the fill valve.

Which stop are you referring to, the main or the one at the toilet? Also, this did not start until I replaced the fill valve.

The stop behind the water closet.

The old ballcock likely had debris built up in the seat, which impeded the pressure of the flow into the fill tube of the Douglas valve -- Installing the new ballcock has likely increased the amount of flow.

Thanks for the reply. I lowed the pressure a bit and that helped with the thumping sound I was getting after the toilet has filled, but I am still getting the gurgling noise from the overflow pipe. We have a low flow toilet, so I am wondering if maybe the fluidmaster just has this effect on low flow toilets. I never had this problem with the old fill valve. I don't get the noise until the flapper has completely closed. If I restrict the water coming out of the tube to a trickle then it doesn't make the noise. Any ideas on what my be causing the gurgling at the overflow tube?

"Any ideas on what my be causing the gurgling at the overflow tube?"

Yes, there's a small tube that runs from the ballcock to the overflow tube. This fills the bowl as the tank fills. The sound you hear is the water running into the overflow tube. It it bothers you then position the small tube so it drains down one side inside the overflow tube instead of down the middle of the tube where you can hear it splatter. Good luck, Tom