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Question DetailsAsked on 11/10/2017

Why is toilet bowl draining on it's own?

Help please! I have a problem with an elderly friends toilet, when the toilet is flushed and re-filling, the water level in the bowl jumps up to almost normal height, but continues to drain out (while re-filling, and afterwards until the water level gets down below the top of the drain tube portion of the bowl). The toilet is on a concrete slab, no evidence of leaking (unless its leaking directly into the sewer line). The supply tube has a regulator on it, and I currently have it set "wide open". She has the exact same toilet & guts in another bathroom, and the one in question is taking about 4x as long to get the tank full & water stop running (all the excess water is going right down the drain). Not knowing what exactly the problem is, I hate to suggest replacing the toilet, I'm afraid she will spend the $ and end up with the same problem. Any suggestions/help would be greatly appreciated! Thanks!

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1 Answer


OK - by "supply tube" I presume you mean at the wall, on the tube leading to the toilet. That should be and stay wide open - it is just a supply/maintenance valve to allow shutting off a toilet to work on it, or for quick shutoff in case the toilet is overflowing and the person does not know how to shut it off in the tank or if the tank is free-draining into a toilet which is plugged and overflowing or about to overflow, or in the event of a broken/leaking tank. Not an adjustment for toilet functioning.

Couple of possibilities covered below - I was not positive I fully understood the situation so covered a couple of alternatives. Read all the way through to decide which applies to your case - may need to a bit of testing to figure out which is your case.

Assuming normal function gravity-flush toilet: Normally, flushing dumps the tank volume (or sometimes only a portion on low-flush / low-flow toilets with full size tanks) into the bowl, which can normally evacuate a lot more water than is coming in - this inflow initially comes out primarily at the bottom of the toilet, from a passageway pointing into the drain tube of the toilet. As flushing occurs (which should be fairly robust, not just a "draining down" as you describe, water is initially continuing to flow from the bottom of the tank into the bowl but then stops as the flapper closes, and a much more limited amount of water continues to flow into the bowl from under the rim. This bowl refill water comes from a small tube from the inlet valve (usually at left side of tank) leading into the top of about a one inch open overflow tube (usually rear of tank behind flapper valve) at the same time as the tank is starting to refill. So - usually flushing occurs in maybe 3-5 seconds, and as the flushing is occurring the bowl refill water is flowing out from under the rim, and continues until the tank finishes refilling - commonly 20-60 seconds. During this time the flushing will end and the bowl will refill to the normal bowl level - roughly at or just above the top of the outlet opening from the bowl.

If the flushing is slow as yours sounds like, it is still flushing (draining out the original bowl water) as it is refilling, and the water level in the bowl can drop below the top of the outlet opening, commonly gurgling in the process as it reaches that level, and potentially stay that low (which can aloow sewer gases in).

If it is flushing slowly (not evacuating the bowl as fast as the other toilet) then there is likely a blockage either in the gooseneck of the toilet itself (which is its trap to prevent sewer gas entry), or maybe further down the line. Since you indicate the other toilet is flushing fine and said nothing about a sewer backup in the lowest elevation drains in the house (check any basement drains including floor drains for backup). But lacking that, sounds like a partial blockage in the toilet or line immediately downflow of it. Pouring a cup or vinegar and about 1/2 cup baking soda into the bowl might clear it out - maybe not. Otherwise it needs to be snaked using a closet snake (a sewer snake with protective sleeve so the toilet is not scratched in the visible portion). COmmonly around $75-150 by a Plumber or Drain Cleaning company.

Now - on the other hand, if the toilet is flushing OK and it is just taking 4 times as long to end the cycle, as you may mean since you said nothing about the bowl overfilling, then if water is flowing down the drain in the toilet in some volume take a look at the flapper valve (about 3-4 inch flapper or vertical lift valve which covers the tank bottom drain hole) when flushing to see first if it is closing OK - on low-flow toilets may close when there is still several inches of water in tank, otherwise roughly as it finishes emptying. make sure the chaiin is not snagging and holding it open. if closing OK as tank empties or near empties, that should stop the draining of the tank (though the refill tube will still be putting small amount of water out under the rim) - if water keeps flowing out of the tank you probably have a leaking flapper valve (or rarely, torn) - try pushing down gently on it to see if that stops the leakage. Sometimes siping the mating surfaces will remove iron algae or minerals or grit causing it to leak.

If pushing down on it stops the extended refill time (as I suspect it will) and lets the tank refill in about the same time as the other toilet, then she may just need a new flapper or tower valve. The tower valve type isw commonly VERY easy to fix - a latch or slide you disnegage to lift it out, replace the gasket that the tower valve comes down on, and put tower back in and engage with its guide. If a rubber flapper valve in the bottom of the tank which the lever pulls up by cord or chain, those are usually easily replaced - just the flapper part if the base is OK, or some models there are press-on mating bases with the flapper which uyou press down with putty on the existing base to create a new sealing surface. That type of repair does not require removing the tank or breaching the watertight parts of the tank. If base tube or mounting or overflow tube is damaged or leaking (pretty rare - usually only due to breakage by someone working in there) that is a lot more work, commonly requiring removal of the tank to fix it. If you are not up to this, a plumber should be able to replace it for $75-175 in most areas - all but about $10-30 or that being labor.

If flapper is good, look at the inflow amount - might be the inlet valve assembly is not flowing as fast as the other toilet - but that would make for slow tank fill and longer running from under the rim, but you would not have water gurgling out from the bottom front tube in the bottom of the toilet. (You can use food coloring to check for flapper leakage. You can also temporarily disconnect the refill tube from the overflow tube and direct it so it flows into the tank - then when you flush, once the flapper closes, there should be no noticeable water flowing into the bowl at all and it should not refill unless the flapper is leaking.

If you want more detail on the replacement flapper valve go to the Fluidmaster website (my favorite toilet parts brand) and download one of the instruction sheets on how to replace flappers or tower valves to see if it is something you are up to.

You can also find some previous questions with answers in the Home > Plumbing link under Browse Projects, at lower left.

SAFETY NOTE - do not put weight on the tank when working, as you can crack it in the worst case, or even a moderate lean on the edge when working can loosen up the mounting bolts and cause a leak which will then require that you shut off the supply valve and drain the tank to replace the tank washers.

Answered 2 years ago by LCD

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