Toilet running randomly even after replacing flapper

[Josh R]

American Stand Plebe toilet
Korky universal fit 2in ch flapper

No leaking anywhere on the toilet.

What can I try next to troubleshoot the leak?

 

[Reach4]

Make sure the end of the refill tube is higher than the overflow. There should be a clip to hold the refill tube above the overflow. How high does the water get? If it gets less than 3/8 from the top of the overflow, the water can be traveling up and then down the tube by capillary action. Set the fill valve to not fill as high. Otherwise, turn off the stop valve that feeds the toilet. Watch how low the water level falls. If it falls to where the flapper meets the seat, the flapper is leaking due to debris or roughness on the seat or not fitting well against the seat any more. Or the chain is too tight.

If the water falls lower than that, there is a leak where the flush valve connects to the tank.

It it stops falling at an intermediate height, there is a leak in the overflow tube.

 

[Sponsor]

 

[Sylvan]

Remove the refill tube, look down the over flow tube and see if water is moving. If it is get ride of the flapper and try a different one

 

[Josh R]

I meant to say no leaking on the outside of the toilet. Obviously something on the inside is leaking.

 

[Jadnashua]

If you shut the water off coming in, and then let the thing sit, does the water level in the tank go down? If so, there are only a few ways that can happen that I can think of:
- leaking from underneath the flapper
- leaking from underneath the flapper seat
- leaking through a crack in the overflow tube
- leaking through the tank bolts
- leaking through a crack in the tank

The first three, you'd not notice any leaks, as they generally end up just going down the drain.

If the level doesn't go down, but the fill valve runs (and it's not overflowing), it could be siphoning because the refill hose is down the overflow. It should have an air gap above the overflow tube.