I want to fill the toilet bowl with water as high as I can and let the water sit without draining for up to 24 hours. Why? To let some (gentle) cleansers do their work. I've tried shutting off the water at the wall and refilling the bowl from a pitcher, but inevitably the water starts draining too soon. Ideas?

  • The only think I can think of is Bernoulli. If it's windy outside, the wind over the top of the vent stack can create a Bernoulli effect and partially empty the toilet bowl. I cannot think of anything else that could cause the bowl to empty except a crack in the bowl itself, which would be pretty obvious. – BillDOe Nov 20 '17 at 22:28
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    It drains because there's nothing actually holding it in - just the curve of the pipe which makes up the 'trap'. You'd have to physically block it somehow to keep the level above its normal 'finished flushing' level. – brhans Nov 20 '17 at 22:43
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    Use a toilet plunger fit the plunger and fill if it is a good seal the bowl will stay full. I have had a young child flush a balloon that got stuck in the trap took a while to figure that one out, finally popped it with a drain auger but if the right size the balloon will make a good seal if the plunger won't seal tight. – Ed Beal Nov 20 '17 at 22:59
  • Use gel cleaner and you won't have to keep the bowl filled. – bobflux Nov 5 '20 at 13:25

The toilet bowl can only hold water as high as the top of the porcelain inside of chamber 5 in the picture below, unless you do something to stop it:

Toilet cutaway

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    Not sure why this answer has so many votes. It explains why the toilet flushes itself, but it doesn't answer the question of how to prevent the self-flush. – FreeMan Nov 5 '20 at 12:29

Fill small plastic bag with one quart of water, remove excess air from bag and tie off. Place in toilet bowl. Dispose of bag when finished in trash receptacle.

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    I'd go further - secure a cord to the bag somehow, or use a very large bag not a small bag. Don't want it going down accidentally. – Criggie May 18 '20 at 7:28

Wad up a large trash bag and stuff it into the bowl, about as far as it will go. If it's not large enough, place a few crumpled paper towels into the bag and re-wad. It should be large enough to clog most toilets, it's easy to remove, and won't seep like a towel or rag would.

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    +1 but I will add that you need to be real careful that you don't flush that bag down when you fill the bowl with water, could make for a bad day. – Jimmy Fix-it Nov 22 '17 at 5:48
  • you can always tie the drawstings around the toilet rim to be sure ;) – dandavis Nov 22 '17 at 6:46

I would try a child's balloon. You'll have to wedge it in tight so it doesn't float up. If you can't wedge it....try a water balloon.

In either case, with a string on the balloon tied to the flush handle or toilet seat.


Here's a completely different solution - to stop the water leaving, stop the air getting in. It will be fiddly but significantly reduces the risk of getting something stuck half way down.

  • Cut a sheet of heavy plastic sheet that fits tidily over the top of the open toilet.
  • Tape the edges all round smoothly and evenly with duct tape, leaving the front flapped back and having more tape ready.
  • Fill through the opening.
  • Flap down the front and tape.

If you can make it airtight the level will stay high indefinitely. More likely a tiny bit of air will get in but it will still hold for a few hours. Use clear plastic sheet and you'll be able to keep an eye on it. Untape carefully starting at the front, and you'll be able to stick it back down if the first treatment wasn't enough.

  • This is good, outside-the-box thinking! I've got to ask if you've tried this. I've poured water directly into the bowl, and it flushes pretty darn quickly. I'd imagine it would be difficult to fill the bowl then close & seal the flap before physics took over and emptied the bowl again. However, I'd be more than happy to be shown wrong on this one. – FreeMan Nov 5 '20 at 12:31
  • @FreeMan I've done it with other things, and a toilet that was draining very slowly, to get cleaner soaking in the bend. Though a toilet drains faster than a sink, the flush allows fast (at least partial) filling. In fact filling using the flush will push air out so a small flap could be left shut but not taped right down. The key is to add the cleaner and any extra water both quickly and through a small gap. Taping around a funnel may also help. Funnels can be made to self seal by putting a floating ball (bigger than the outlet) in the bowl. – Chris H Nov 5 '20 at 12:47
  • ... I'd consider experimenting, but I got rid of some bits of suitable sheet in this morning's rubbish collection and don't think I've got any more – Chris H Nov 5 '20 at 12:48

I got it done but it is not as easy as one might think. Most of the time there remain some gaps water uses to drain out, and after a couple of minutes, water level is back to normal. So it is required to apply some kind of pressure all around the toilet bowl.

The best solution I have come up with involves using a garbage bag and a plunger.

  • Fill the garbage bag with water at 25% and stick it down the hole.
  • Put the plunger inside the bag so the bag adheres to the bowl, as depicted below.
    • If you press hard enough, it should be sealed tight enough.

Even with this technique, water level only holds for 1 or 2 hours, which is barely enough for cleansers to do their job.

bag and plunger


i hate to just plug a product but on tv flex tape looks like it may work. he literally takes a piece and pluggs up a above ground pool by taking a piece of the tape and literally plugging it from the inside of the pool. so the tape can get wet and still stick. enough pieces, im sure would make a perfect seal. and then just peel once done.

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