falling water level in toilet bowl

As it's happening on two loos, there is a common factor, which must be something pulling a vacuum on the sewer. Dynorod?
 
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did it make any difference when you tried propping the nearby cover open to prevent any suction?
 
Hiya,

No, didn't seem to make a difference, the water level is still dropping even with the drain lid raised.

To answer another question, yes we have a toilet upstairs. This is fine though, water level is sitting in the same place it always has.

Someone else mentioned it may be a venting problem caused by the upstairs toilet... would it be worth testing the pipes with a smoke pellet?
 
what is the floor made of that this magic WC sits on?
 
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Hey,

The toilet is sat on a concrete floor, around that is just some wood laminate. Toilet basically runs straight down into the sewer system, I can't see any vents or anything.

I've had a good look all around the toilet and there are no cracks anywhere, the seals are all still well in place and when you flush you can see the water running clearly and fast down into past the manhole cover.

It's a real mystery, the guys from South East Water had a good look round as well, they said the toilet is fine and the pipes are fine, it's just one of those things and nothing to worry about..... but I can't see how it can be just one of those things when I don't know what that thing is. I mean toilets don't just empty themselves for no good reason, there has to be a reason.

So my quest continues... just not sure where?
 
it sometimes happens round here under strong winds/coastal gales. Anything like that?
 
How far is the coast? Tsunami on the beach in Berkshire???? :LOL: :LOL:
 
How far is the coast? Tsunami on the beach in Berkshire???? :LOL: :LOL:
Diabetic Labrador?
 
Surely, this has to be a process of elimination.

1. take the toilet out, fill with water and watch the level.
2. Stuff drain rods down it, and ensure its not blocked.
if all ok, its not a problem with that specific leg of the drain.

3. if you cracked the lid of the nearby manhole, then its not suction being caused down stream.

4. It must be suction being caused by something else drianing into the same drain from up stream.

so i would hazard a guess as a blockage in the soil vent pipe, something like a bird nest or dead bird..

Its the only possible thing left.
 
My son aged about three came out of the bathroom with a mug of water. He couldn't reach any of the taps...
 
Surely, this has to be a process of elimination.

1. take the toilet out, fill with water and watch the level.
2. Stuff drain rods down it, and ensure its not blocked.
if all ok, its not a problem with that specific leg of the drain.

3. if you cracked the lid of the nearby manhole, then its not suction being caused down stream.

4. It must be suction being caused by something else drianing into the same drain from up stream.

so i would hazard a guess as a blockage in the soil vent pipe, something like a bird nest or dead bird..

Its the only possible thing left.
5. put a piece of hose round the trap so that it vents the drain beyond :idea: then leave for the hour that " things happen " :eek:
 
Have this problem in the upstairs toilet and not the down. During strong winds as the air blows over the top of the stack it will create a vortex with the relativly warmer air from your poo pipe. I have taken the time to connect a manometer to the stack itself and can see as the wind blowns a negative presure of -5 mbar. Thats a fair bit of suction consdering a boiler fan opperates at around -3 to -5mbar. The water also moves in relation to the manometer. Solution fitted auto air admitance valve (dago) to top of stack.
 
I'm with TonyW2 ... it's the dog. Solution - keep the lid closed.
 
As the pan is flushing and running OK to the manhole, yet the water level is still dropping with the manhole cover open, then it would have to be a hell of a suction source, as the drain from WC to manhole is open to atmosphere.

Have we ruled out a double trap syphonic suite?
 

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