# Disappearing Water in Toilet Bowl



## Jend (Mar 5, 2008)

Help! The toilet in the upstairs bathroom of my townhouse fills but then the water gradually disappears out of the bowl. I don't see any water marks on the ceiling downstairs so I'm hoping it's not leaking anyplace. There is no water on the floor in the bathroom either. There is no sewer gas smell either.


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## nap (Dec 4, 2007)

do you have a dog?


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## Nestor_Kelebay (Jun 17, 2008)

Has it always done that or did you only notice the bowl doing this in the winter?

If it only happens in the winter, I'd suspect the culprit might be that the vent stack on your roof is clogged with frost.

In winter, the vent stack in your house can act like a chimney with warm moist air from the city sewer rising out of that vent stack 24/7. As it approaches the top of the vent stack where it's cold, it can form frost on the inside of the vent stack. If enough frost forms, and gets covered by snow, you can have a clogged vent stack.

Then if you drain a bathtub or the clothes washer spins, you get a lot of water added to the drain piping in your house in a short time. If your drain line isn't clogged, that water can flow away just as quickly. However, if the main drain line from your house is partially clogged, that water can back up in your drain piping. And, as the water in that drain piping drains away through that partially clogged line, the suction it creates in the drain piping could suck water out of the toilet bowl.

If that's what's happening, you should also see water being sucked out of the p-traps under your sinks, too.

Get a garden hose or clear vinyl hose and push it into the exit hole of the toilet bowl while twisting the hose to get it in as far as it will go. (Don't use a short hose; you want to be sure that the hose doesn't accidentally go down that bowl.) Then blow into the hose hard to eject any water in it into the toilet's drain pipe. With that empty hose in place, any pressure in the vent stack can escape through the hose, and any suction in the vent stack will be quenched by air coming in through it.

Keep the door to that bathroom closed to prevent sewer gas coming into the rest of your house.

If that seems to solve the problem, I'd probably get your main drain line cleared by a plumber.

It can be dangerous to walk on a snow or ice covered roof in winter. However, if there's a taller building around you can see your roof from, or if you can see your vent stack from the ground or from a ladder placed against the evestrough, maybe see if the vent stack is covered with snow. Normally, the snow will fall harmlessly into the vent stack leaving a hole in the snow cover over the roof.

The only other things I can think of are evaporation and a cracked toilet bowl. A cracked toilet bowl would explain it, but I don't know how quickly the bowl empties to know whether evaporation is a feasible possibility. And, of course, the dog theory.


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## Jend (Mar 5, 2008)

Thanks for the info. I noticed it last night after I took a shower in another bathroom upstairs. I flushed it and it seemed fine. This morning I checked and flushed it and it seems ok. I take my shower at night so I will see what happens. If it does it again then it may be clogged.

(No dog in home either) :wink:


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## boman47k (Aug 25, 2006)

Nestor? Are you talking about a siphoning action? If so, I can't really see how the water can be siphoned from the bottom of the toilet. I mean how does it get sucked out and over the hump in the drain channel of the toilet? Not disagreeing, just don't understand.


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## DUDE! (May 3, 2008)

that sucker has to have a crack in it somewhere, that would be my guess, could be following the pipe down to the basement.


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## krazni (Jan 6, 2009)

Does the toilet bowl empty completely, or just mostly, leaving standing water in the bottom inch or so?


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## Nestor_Kelebay (Jun 17, 2008)

boman47k said:


> Nestor? Are you talking about a siphoning action? If so, I can't really see how the water can be siphoned from the bottom of the toilet. I mean how does it get sucked out and over the hump in the drain channel of the toilet? Not disagreeing, just don't understand.


Well, if there's enough of a vaccuum created in the vent stack as the water in the main drain line drains away, I'm thinking it could suck enough water into the discharge channel to leave it looking like the water level is low. It might even initiate a flush if the suction is strong enough.

The idea of a clogged vent AND a partially clogged main drain line is the only thing I could think of to explain the lowering water level in the bowl (besides a cracked bowl and the dog theory). A cracked bowl would seem to be more likely on the surface, but a cracked bowl would leak all the time, not just in winter. There's no dog, so we can't chaulk it up to Fido.

And, I guess we can rule out the possibility of thirsty burglars taking a sip out of the bowl...


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## leedawg77 (May 26, 2012)

nap said:


> do you have a dog?


I am very embarrassed to admit it, but your answer actually answered my issue. A certain 4-legged house member has been "siphoning" water out of our bowl. I was looking for cracks, checking the vent stacks, etc. Wow.


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## M3 Pete (May 10, 2011)

leedawg77 said:


> I am very embarrassed to admit it, but your answer actually answered my issue. A certain 4-legged house member has been "siphoning" water out of our bowl. I was looking for cracks, checking the vent stacks, etc. Wow.


Thanks for joining the forum to share your embarrassment.


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## boman47k (Aug 25, 2006)

leedawg77 said:


> I am very embarrassed to admit it, but your answer actually answered my issue. A certain 4-legged house member has been "siphoning" water out of our bowl. I was looking for cracks, checking the vent stacks, etc. Wow.


Heheh, good call Nap!
Sometimes the answer is right in front of us..or behind us...., or under our feet. :laughing:


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