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Question DetailsAsked on 12/9/2015

My toilet tank keeps refilling; replaced flapper and gaskets still refilling, what is the problem?

When I turn the water supply off to the toilet, the reservoir tank empties. If it's not the flapper or the sponge gasket, what else could it be?

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1 Answer


About a dozen reasons this could be happening - most common is probably kinked or snagged flush handle chain or cord, or needs new flapper valve.

1) if staying full but toilet is running continuously, check the height of the float setting - may be set so high that the water is going into the overflow tube (about 1 inch diameter tube towards back of tank, top should be about 1/4" above high water line. Since you said tank empties when water is turned off, not this because water level would stop at top of tube when draining down with water off.

2) seal around fill valve mounting stem is leaking - which would be draining the water onto the floor under where the flex water tube goes into the tank, or running down the tube to the floor, so that would be real obvious if that were the spot

3) cracked toilet tank leaking - would normally be putting water down the side of the base onto the floor, or dripping directly off the bottom of the tank

4) cracked toilet tank right at the outlet hole - so water is leaking from tank directly into the bowl via the normal route - if you put a bit of food coloring in the tank at the bottom, would show a flow toward the bottom of the flapper housing - though this would also happen with 5) below and 7) through 9). Would not be able to detect without removing tank to inspect - which would be necessary also if a flapper/flush valve assembly gasket or seal leak

5) leaking gasket/seal around bottom of the overflow tube housing, if it is separate from the flapper housing. Some older toilets, a few new ones, have 2 holes leading to the bowl from the tank - flapper/flush, and overflow. Most modern ones the overflow is integrated into the flapper/flush hole so both overflow and flushing water go down through the same hole through the tank into the bowl - but would result in constant "running" of the water into the bowl, and intermittent or "ghost" refilling of the tank.

6) leaking tank bolt gaskets - would be dripping onto floor from underside of tank so would be obvious

7) leaking gasket at the base of the flush valve housing where it goes through the tank - there is a rubber or similar gasket, or occasionally a putty ring, there - between a flange on the bottom of the housing and the bottom of the tank. The black gasket shown here -

note they have the nut screwed onto the bottom thread as it usually comes in the box - in use the bottom housing thread passes through the toilet tank with the gasket (black here) opr occasionally puty ring sealing it to the bottom of the tank - then you would have the bottom of the tank itself with the thread passing through it - then the hex nut threaded onto the threads to compress the gasket and hold the flush valve rigid to the tank. If leaking there, tank would go basically dry - just a touch of water in the uneven bottom of the tank. The large soft "foam" or "spongy" seal like this -

then goes onto the threads up to (or more commonly over and around) the nut and seals the tank to the bowl - sometimes with a bracket clamping it with the tank mounting bolts as shown, usually just fits around the thread extension and you place it by lowering the tank onto the bowl with the mounting bolts already installed in the tank.

8) leaking flapper seal - deformed or softened flapper, or grit or slime on the mating surface of the flapper or the contacting surface at the housing - wipe off with paper towel, and see if the flapper appears to be warped or deformed - or partly unhinged. Also, look for the cord or chain that lifts it being hung up on something because it is too long, or a piece hanging down and holding the flapper partly open. A little slack hanging down is OK, but should not reach the edge of the flapper.

9) for Mansfield type with a tubular plastic combination float/seal (flapperless toilet) like this, which work really slick and for a long time and VERy easy to replace the gasket -

the plastic column float comes down on a rubber gasket in the outlet housing which can easily be replaced

10) cracked overflow tube - the tube itself or where it comes out of the housing - water would be flowing into the tube which you should be able to see if you shine a flashlight down in there

11) if it has been fixed with a kit in the past, the matching sealing surface that the flapper contacts may be a press-in type, with a gooey putty seal under it (gray ring in the image), which can leak like this - is pressed down onto the original sealing surface.

12) chain/cord connecting flush lever and flapper too short or hung up or kinked

When you say the sponge gasket, if you mean the large one UNDER the tank, at the contact with the bowl - that only stops water from overflowing down the side of the bowl when flushed - does not hold water when tank is just sitting. There is another gasket, sometimes rubber or such but sometimes a putty, where the flapper valve/overflow tube housing penetrates the bottom of the tank as in the images above. There is also commonly a seal, commonly gray putty ring, that goes under the flapper seal (especially on rebuild kits) - the bottom half of the flapper/base unit. When installing a replacement flapper housing, it is pressed down into the putty or gasket.

When the tank drains down (with water totally off - if drains basically dry, then #7 would be the most likely, though #4 would be a possibility, though uncommon - usually any cracks start at the bolt holes

If the water stops dropping shortly after it reaches the flush (flapper) hole, try (as it is nearing empty) manually opening and holding open the flapper while you shine a flashlight down in there - see if the water stays at that rim level (meaning leaking flapper is the problem, or if water is still flowing into the hole through the flapper seal gasket/putty. IF not flowing in there or drops below that level, then probably the bottom gasket on the housing, where it passes through the tank, is the problem. Would not be able to see that water coming in because it would be passing outside the housing threads, between them and the tank itself, but would hear it running down into the housing and bowl.

Flapper/drain kits are cheap - typically about $20-30 from Plumbshop or Fluidmaster (my favorite brand) - come as complete rebuild kits with inlet valve assembly, flush assembly, and handle assembly - or you can buy each assembly individual - also only the flapper itself. Not real tough to change them out yourself provided you get the right kind of kit (similar arrangement). Is a 2-3 hour job or so first time around and you may well need help with handling the tank so you don't drop it - about 1/2-3/4 hour job once you have done it once. Do NOT try balancing the tank on the toilet seat while working on it - spread a thick towel on the vanity countertop so it won't slide off easily - I have seen too many tanks broken that way, by pros and amateurs both.

Minimal plumbing skills or tools required screwdriver, cutting tool, channel locks usually handle it - instructions tend to be fairly good and manufacturer websites have how-to videos, and of course lots of Youtube videos. Main thing to watch out for is overtightening of nuts, as the porcelain tank cracks moderately easily, especially it you overtighten the mounting bolts to the bowl. Course, not enough tightening they leak - but that can be fixed without removing anything by just reaching down into the tank with screwdriver while someone holds the bolts - better that than cracking the tank over-tightening them. I would rate it (first time around) about a 6-7 on a scale of 10 for DIY homeowner difficulty - about a 3-4 second time.

Professional - to track down and likely replace the flush valve assembly (and if doing that I would have them replace the fill valve too - additional 2-3 minutes and maybe $15 while there) - normally minimum Plumber service charge of about $75-150 plus normally not over $50-60 total parts to rebuild the whole innards of the toilet with a kit.

Answered 4 years ago by LCD

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