Fluidmaster 400A shuts off but then slowely fills to the top of the fill tube

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walt_pittsburgh

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This was installed a few years ago and has been fine until recently. I have the float to fill to around 1" below the top of the fill tube when it will shut off, but after an hour or so, (it must run very slowly) it will increase the water level right to the top of the tube or just below the top (1/16" or so). It would appear I am leaking somewhere. I tried cleaning the flapper to no avail. I also did the food coloring test, with very faint indication of a seeping. What bothers me is why does it seek a new level after the valve first shuts off. Is this related to a bad fill valve?
 

Reach4

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Replace the fill valve. It is usually pretty easy to do. Some people prefer the Korky fill valves. This overfill problem is not related to the flapper. Now if you are getting leakage before the water rises to the overflow top, then there are kits with a new fill valve and new flapper valve packaged together. Heck, while you are at it, have you been thinking of getting a new toilet? If so, this would be a good time to do that.

If the shutoff valve under the tank is not so good, it would be a good time to replace that with a new 1/4 turn ball valve at the same time.
 

Jadnashua

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FOr a couple of dollars, you can replace the seal on a Fluidmaster - it takes all of a couple of minutes and does not require any tools. The instructions are on the seal's package. Essentially you turn the shutoff at the wall off, lift up and twist the tower, it comes apart, remove the seal, put the new one in its place, then reinstall the top of the fill valve. At least, that's how the older ones worked - I do not think they've changed that part of the valve. SOme love the FLuidmaster, some prefer the Korky. The Korky quietfill IS quieter in operation and the shutoff is smoother so things don't tend to create a thump or move around when it stops filling. It also has a replaceable seal, so the next time, you don't have to replace the whole thing (rare on either the Fluidmaster or Korky that they can't be fixed with just replacing the seal).http://www.fluidmaster.com/downloadable/download/sample/sample_id/300/
 

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walt_pittsburgh

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Thanks everyone for your input. I went with the new seal and that solved the problem, but I also purchased a new fill valve just in case I needed it. We have 3 toilets and one is still the original Universal Rundle mechanism. I also put in a new 1/4 turn brass shutoff. The original plastic shutoff did not work any more. I hate turning off the whole house for one fixture. Thanks again.
 
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