Toilet problem that's baffling me

[caretaker]

...Went into work this morning and found the bowl in the middle toilet of three bone dry with dry toilet paper in the bottom although there was water in it on friday and no one has used the toilet or adjacent ones since. Strange I thought but not half as strange as when a few minutes later I went to another run of toilets about 20 yds away and found exactly the same in another toilet also in a run. So a few things that are baffling me. If there was a blockage in the system how come the toilets either side were not affected. If the problem was caused by such and a syphon effect induced into the system surely this would only draw the water through until the upper level of the water reached the upper part of the U bend at which point the seal would be broken allowing the remaining water to flow back into the bowl. Both systems enter different manholes outside as well!!

Any suggestions gratefully received

 

[stevetheplumber]

do you have a dog?

 

[caretaker]

yes...and I have asked her and she is none the wiser either, Quantum Physics is more her line.!

 

[dontknowitall]

I reckon this is a syphoning problem. I'm wondering if a vent pipe has become blocked somewhere?

 

[caretaker]

But surely if that was the case and water was being syponed into the main soil pipe, as soon as the level of the water reaches the top of the inside of the U bend 'if you see what I mean' the pressure will be equalised between that of the toilet bowl and the syphon thereby resulting in the water that was being syphoned running back into the bowl thereby leaving an inch or two in the bottom.

 

[stevetheplumber]

i agree it cant syphon every last drop out and i cant imagine it would evaporate what was left over night have you tried refilling and flushing all the toilets at once?

 

[tipintim]

Must be a hair line crack, then water seeping under floor covering.

 

[SimonG]

do you have a dog?

 

[caretaker]

Must be a hair line crack, then water seeping under floor covering.

As I said, it happened to two toilets about 20 yrs apart at the same time with each toilet being in the middle of a run. Definately no crack in either bowl.

 

[Deleted member 25704]

Its most likely due to hairs stranded together creating potential for caplilarity. It could be a piece of paper or towel snagged on the bend (caught on internal abrasion) but imersed to create siphonage.

I have come across two WCs in one house, bought from same retailer (bathroom store). The bottom of the WCs were porous, hence water just percolated through ceramic over night. We had the same with one basin, but less of a problem (made in China).

Other problems also mentioned such as vent problem - this might be more associated with 'waving out' as wind blows over vent, the pressures inside the stack change and particular wcs might lose their seal due to waving.

Also - induced siphonage if connected to other wcs (lack of sufficient ventialation in system). Mutiple appliances flushed at same time can also create problem - remember cinemas have the most beautiful fully ventilated sanitary systems.

Also compression, if connected to high rise and situated on ground floor.