Empty Toilet Mystery

Yet another toilet thread, I'm afraid ...
Out downstairs loo was originally an outside lavatory but it's been turned round at some stage and the toilet now backs onto the outside wall.
The waste goes down into the concrete floor and under the wall and, presumably, somehow makes its way to the stack about 3m away. There is no access to it at all, so I hope I never have a serious problem!
For two or three days it has been emptying much more than usual. The water level doesn't quite reach the inside corner of the bend, but it's not far off.
We're having a slight thaw today and I noticed about half an hour ago that it seemed to flush normally, with the water level reinstated to the usual level. From this I presume that the freezing weather has some bearing on this but I can't puzzle out how or why.
What does the panel think?
--

Terry

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Terry Casey wrote:

There will be a blockage somewhere down the line causing a slight vaccuum, and it doesn't go to the stack, that is to say, this particular drain is unvented, because if it was, a vaccuum couldn't be formed. Ice probably had something to do with the blockage.
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Phil L
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Terry Casey pretended :

My guess would be that the vent is blocked thus allowing the suction of the water going down, to draw the trap water along with it. Is it one of those automatic type flaps at the top of the stack, which has perhaps frozen shut?
--
Regards,
Harry (M1BYT) (L)
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snipped-for-privacy@NOSPAM.tiscali.co.uk says...

Not as far as I'm aware - I think it is just open at the top. The house is about 105 years old and so, probably, is the stack!
The upstairs toilet, which definitely goes to the stack, is fine.
However, I've no idea where the drainage goes - there's nothing obvious in the street (loos and stack at rear) and a neighbour suggested recently that the sewer runs under the back gardens, so the downstairs toilet might be connected en route.
Does that help?
--

Terry

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On 21/12/2010 17:28, Terry Casey wrote:

Some houses in the fifties (and probably earlier) had a near ground level sewer vent fitted with (IIRC) a mica flap in a forlorn attempt to make the vent one way. If you have such a vent it could easily have been blocked by snow.
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Terry Casey wrote:

Like I said earlier, the outside toilet isn't connected to the stack - they never were - they used to have an 'interceptor', like a open drain with a small steel grate over it, and you could watch all the little jobbies making their way to the sewer, but these often got paved over, meaning the toilet is now directly connected to the sewers with no vent. Your upstairs one is also directly connected to the sewers, but it's vented via the stack, as are 99% of toilets these days.
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Phil L
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