stubborn toilet block with unusual symptoms

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I am dealing with a toilet with a stubborn partial blockage (i.e. very slow draining) which easily becomes a full blockage with too much waste.

However, it has a curious characteristic in that, when allowed time to drain, the water in the bowl empties almost completely, i.e. goes much lower than it would during normal unblocked operation.

How is that happening, some kind of strange siphoning effect?

I plunged the absolutel #!&% out of it on a number of occasions and am still not getting the whooshing unblock event that I hope for.

Any ideas? Is it possible that it's backed up further down, into the drains? I've unblocked toilets a bunch of times before and normally, if the over-fill-the-bowl trick doesn't work, one quick plunge will do it. But this is just solid, won't clear.

Any ideas appreciated. I guess I may have to take the pan connector off and go in that way...
 
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Follow your soil pipe up to see where it goes, so far as I am aware - they can be inside or out, installed at the top of the pipe. The only way it can syphon, is if the pan contents being flushed, can draw the entire contents out. The idea of the AAV is to allow air in to prevent syphoning. If it lacks an AAV, it will just be an open vented pipe sticking up above your roof eaves, perhaps that has become obstructed?

Does the water in the washbasin/bath U bend get sucked out as well?
 
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Had plenty of wc pans that have done that (no aav either), usually just a direct drain connection with a blockage. Obviously something is pulling the trap. Have you tried lifting external manhole covers to locate blockage? If it ain't going with a plunge it's going to be something more stubborn like wipes, grease, roots etc.
 
If plunging hasn't cleared it, then its highly unlikely the blockage is in the pan. Whereabouts is the WC located for a start? Ground floor or 1st floor. If on ground floor, does it connect into a stack, or straight into the drain? First port of call would now be to trace the run to outside, and check any chambers for signs of an issue.

Any AAV will usually be internal, and either boxed in or in the loft space. If an AAV is fitted it should be opening to let air in, rather than the WC trap syphoning.
 
Thanks for the replies, guys. To answer some questions - the toilet is ground floor (in a SS extension to rear) and I believe it goes directly into the drains, but there is also some kind of vent-like pipe (rising just above the roof of the SS extension), that comes out of the ground outside near the relevant wall.

The extension is built OVER the manhole cover, but when I renovated the bathroom I built a wooden trap door over the cover, a rim around it, and then flooded the levelling compound around it all to the same height. Lino/vinyl stuff over the top. Perfectly flat and should be possible for me to roll the vinyl back and get at it! What a chore, though. Would there be any merit it taking off the pan connector first, as a simpler step before going into the manhole cover?

Cheers, I'll see what's in there.
 
What is at the top of the vent pipe, any chance of a photo?

If it get to looking at the drain, you certainly will be better lifting the vinyl and cover.
 
What is at the top of the vent pipe, any chance of a photo?

If it get to looking at the drain, you certainly will be better lifting the vinyl and cover.

I'm away from home currently, so no photo until Monday - but iirc it's just an open-topped pipe with a metal grill on top, like a chimney protector kind of thing.
 
Might be worth checking a neighbouring manhole if that’s more accessible? Also depending on your run/connection the blockage could be after your manhole anyway.
 
I doubt removing the pan will achieve anything, other than needing you to replace the pan connector, as it's guaranteed to leak if you try to reuse it... You may be able to get rods down there and shift any blockage, but if that doesn't work, you'll need to lift the manhole anyway, although, if there is one downstream outside the footprint of the building, I would check that first to rule it out.


Does anyone use wipes, sanitary products, anything like that and flush them down the toilet? All are liable to cause a blockage.
 
SOLVED

It turns out there was a blockage in one of the manholes about eight houses away (I am the start of the run). I and a few neighbours had a good old poke around in there and did manage to loose it, and we got it moving into the next manhole. The story might not quite be over just yet, though, but that was definitely the issue!

Thanks, everyone.
 

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