[kimswim]

I flush and the tank fills perfectly, silence. Then the tank water level starts dropping -enough to cause a short refilling of the tank. This goes on and on. I am wondering which part to replace. All parts inside the tank look good. What could be leaking? The floor is dry. This toilet is not the black flap kind.
Thank you any plumbers out there. I have 8 toilets just like this one in apartments!

[hkstroud]

This toilet is not the black flap kind.

What does that mean?

You either have a leaking flush valve (flapper) or you have the refill tube, that little tube from the fill valve to the over flow pipe, stuck down in the overflow pipe below the maximum water level of the tank.

[Milo Dolezal]

Agree with above post. Most likely it is bad flopper.

[speedball1]

If you don't have a "black flapper" (see image ) then please describe what you have. In the meantime you might wish to check the rest of the tank adjustments.(see image). Check the tank water level, it should be at the mark in the tank or 3/8 to 1/2" below the top of the over flow tube. Now look at the flapper, If it has wavy edges on the flat surface, replace it. The linkage between the flapper and the flush lever should have 1/4" play when the tank is filled. Also, check the small tube coming out of the top of the ballcock and make sure it's connect to and draining into the white overflow tube. Hope this helps. Tom