This is just some information that most plumbers will be aware of but maybe not many DIYers.
I live in a bungalow and this morning I found that the bowls of both toilets stayed half full after being flushed. Thinking both toilet waste pipes combined before entering the external manhole and that there was probably a blockage where the waste pipes joined I lifted the manhole cover. To my surprise I found separate pipes from the toilets but the manhole was half full of liquid etc.
The next manhole, about 4 yards downstream was also half full but I managed to poke around with rods in the second manhole to locate the outlet pipe entrance. On rodding the outlet pipe I cleared a blockage and the manholes and toilets quickly drained much to my relief.
My point in relating this episode is to show that if a toilet bowl will not clear the problem may well be, but occasionally may not be, due to a U bend blockage.
I can only surmise that if the manhole, into which the toilet drains, does not itself drain then air pressure inside the manhole will build up and stop toilet bowls from draining. If what I surmise is true I personally am surprised as I am sure the manhole cover is not air tight. Whether this would happen in a house where the toilets are at first floor level I do not know. It may be that the manhole would fill first and leak onto the surrounding ground before the toilets were affected.
I live in a bungalow and this morning I found that the bowls of both toilets stayed half full after being flushed. Thinking both toilet waste pipes combined before entering the external manhole and that there was probably a blockage where the waste pipes joined I lifted the manhole cover. To my surprise I found separate pipes from the toilets but the manhole was half full of liquid etc.
The next manhole, about 4 yards downstream was also half full but I managed to poke around with rods in the second manhole to locate the outlet pipe entrance. On rodding the outlet pipe I cleared a blockage and the manholes and toilets quickly drained much to my relief.
My point in relating this episode is to show that if a toilet bowl will not clear the problem may well be, but occasionally may not be, due to a U bend blockage.
I can only surmise that if the manhole, into which the toilet drains, does not itself drain then air pressure inside the manhole will build up and stop toilet bowls from draining. If what I surmise is true I personally am surprised as I am sure the manhole cover is not air tight. Whether this would happen in a house where the toilets are at first floor level I do not know. It may be that the manhole would fill first and leak onto the surrounding ground before the toilets were affected.
