Our downstairs toilet seems to half-empty itself after flushing. I am sure it never did this before. You can flush it, it seems normal, and half an hour later the level in the bowl has dropped by a few centimetres.
What could be going on? There's nowhere for it to go other than escaping by climbing over the U-bend, and no sign of any leak. I am pretty sure that no-one in the household is siphoning it away or drinking it.
Daniele
A change in behaviour (if it didn't always do this) can be caused by a blocked sewer. Levels changing in the sewer can suck U-traps whereas they would normally be better vented when the system isn't full of you-know-what.
Usually means its about to block. Now is the time to use some checmicals to dissolve some of the blockage - much harder to do once it has blocked.
Caustic soda Sulphuric acid but not together!
NT
,
There are three possibilities I know of: a leak, trap sucking and wind.
A hairline crack in the ceramic below the water level might well be hard to spot, especially if it's round the back and the floorcovering allows the water to disappear under the fitting rather than appearing in front. Moving the floor covering and getting right down there with a mirror if neccessary is unpleasant but could be worth it.
Andrew's description of a blocked sewer shouldn't be able to cause the effect as there is supposed to be either an Automatic Air Vent or an open pipe to allow plenty of air into the sewer. Now in the real world things don't always go to plan and Andrew is of course correct that a blockage could be sucking out the trap.
If it's particularly windy where you are you might find that air flowing over the top of the open vent pipe can cause this - sort of a special case of the trap being sucked out. In our house it only ever happens if there's a gale blowing from the north.
Good luck, Calvin
The level in our downstairs toilet took to falling to normal when flushed with a slow rise to a little above normal over the following minutes. All in slow motion (sorry, couldn't resist!).
The manhole outside, some 4 feet deep, was full almost to the top with 'stuff' of quite a viscous consistency. The 'slurp' as it went was quite satisfying.
You may wish to investigate with this in mind whilst holding a long pole and with the wind to your back!
Your drains are partially blocked, or it's windy.
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