I think you already have your answer (look at the fill valve). When the fill valve stops working well, it continues to fill water into the tank even when the tank is full and the ball mechanism is pushed up by the water in the tank You can tell by looking to see whether the water level in the tank is right up to the edge of the overflow.

It is a very easy repair because you can install a new, inexpensive fill value, like this:

http://www.homedepot.com/p/Fluidmaster-Universal-Fill-Valve-400ARP25/100554467

The other thing that happens to me, sometimes, is that crud (for lack of a better word) gets on plastic part under the flapper (the flush valve) and prevent the flapper from sealing. Try wiping under the flapper with a paper towel.

You need to adjust the mechanism (float usually) that determines when to stop filling. It's overfilling and hitting the bypass. Usually it's just a screw on the float to adjust this.

If the toilet is that old get a new one. That thing probably uses three gallons of water per flush.

Anonymous wrote:If replacing the flapper didn't work, replace the valve and float. I just did it myself and it wasn't that hard. Most toilets take a standard valve that costs about $8 but there are a few models that need very specific valves that you'll have to identify and order.

Thanks for the input. The toilet is an American Standard Plebe from 1980. I don't see how the fill valve could leak water out of the tank unless it ended up on the floor. The fill valve is incoming water under pressure so water can't be back flowing that way. However, if all else fails I'll give it a try.

Thanks

Anonymous wrote:If replacing the flapper didn't work, replace the valve and float. I just did it myself and it wasn't that hard. Most toilets take a standard valve that costs about $8 but there are a few models that need very specific valves that you'll have to identify and order.

This. HD has Universal valve/floats.

If replacing the flapper didn't work, replace the valve and float. I just did it myself and it wasn't that hard. Most toilets take a standard valve that costs about $8 but there are a few models that need very specific valves that you'll have to identify and order.

It isn't the tank seal...you would have water all over your floor!

The answer really depends on your model of toilet. It is somewhere within the fill/flush mechanism. If an older model, yes the flapper and its related chain/rod are the culprits. If a newer model, could be anywhere in the fill/flush area. You should be able to figure out the type/model of toilet by the writing on the inside of the bowl, and from there a little google will go a long way.

I have a toilet that runs every 15 minutes or so.
The first thing I did was replace the flapper. That did not work.
Then the guy at Home Depot said to replace the tank to. Bowl seal. Si I did. That didn't work
Then I added a gasket for the flapper to seal against. That didn't work either.
Any one have any suggestions on what else I can fix (preferably that will fix the problem)?
There is no water on the floor so the water is leaking from the tank into the bowl.

Many thanks