Drainage problem

[MickBrown]

Went to a house where there is a problem with the toilet in the bathroom constantly blocking up. The soil stack is in the corner of the room and the toilet about 5ft away with a 110mm soil pipe under the floor, in between the soil stack and the toilet is the basin which also drains in to the 110mm pipe. The customer says when the toilet blocks he runs the basin taps, air comes up in the toilet pan and then after a short while there is a 'whoosh' and everything clears. My theory is that soil pipe may not have a fall on it, maybe even a negative fall. The waste does not flush out of the pipe and builds up, when the basin tap runs it forces any air in the pipe back up through the toilet until the pipe is full and then the weight of water then forces everything down the soil stack and the blockage is clear for a while. Unfortunately the problem did not occur whilst I was there and so only have the customers description.
I need to go back and take up the bathroom floor to have a look but any other ideas to take with me would be appreciated.

 

[petercj]

First question I would ask is whether it's always done this, and if not, what's changed to cause the issue?

If it's a recent problem, have they put anything down the toilet that might have created the tendency to block, such as dental floss, which might be caught up and stopping a smooth flow when the pan is heavily loaded. Presumably the cistern hasn't been changed or altered, thus reducing the capacity of the flush?

 

[tamz]

Check if the basin waste connected by a rubber boss adaptor. If it is the basin waste is probably inserted past the boss into the pipe.

 

[MickBrown]

Thanks Peter, the customer has not done anything to it since he moved in and it has done this all the time, however I suspect that the previous owner has made alterations unless the toilet was fitted badly by the builder. The toilet pan connector goes 90 deg down, however the soil pipe is too far away from the wall and it has a slight angle on it to allow the pan connector to fit. Even then the wall has been built out behind the cistern about 25mm to enable the pan connector to fit at all. The bathroom is big enough to be designed much better than this and so I think a previous owner has moved the toilet, if it looks a bit of a bodge job above the floor then what could lie beneath! Fortunately the floor has sticky vinyl tiles that come up quite easily so I should be able to access the pipe okay. If the floor underneath looks like it has been taken up after the house was built then I will know that changes have been made.
If originally the toilet was closer to the soil stack then the branch connector may have been quite high in the void under the floor, okay for a nearby toilet but would need lowering to get a fall for a toilet further away. Of course for a DIY job this may be too difficult so they just added 5ft of pipe with no fall or like I said even a negative fall.
I'll find out in a couple of days when I go back. Thanks about the floss, didn't think of that although I planned to check for any blockages or lips on bad joints.

 

[MickBrown]

You were almost right tamz. I had actually thought of that and already checked it, today I went back and took the toilet out and the floor up. Sure enough there was no fall on the 110mm pipe but I did not think that would cause constant blockages. Looked down the pipe with a mirror and could see a blockage about 5ft along, when I eventually cleared the blockage I could see the waste pipe for the shower protruding in to the 110mm pipe almost the full depth. This was what everything was getting caught up on. Above that end of the 110mm soil pipe is the back of the shower which had been built out about 20cm to allow for pipework for the shower and at the far end of this boxed section is the main soil stack. The side of this boxed section was tiled, the current owner had done this and told me that he had screwed a length of hardibacker board up the side before he tiled it. I took the tiles off till I reached a join in the board and then took off the board and I then had access behind this built out section and to the waste. I pulled the waste out and cut off nearly 4 inches of the pipe and reinserted. I chocked the horizontal soil pipe so it now had the correct fall (there was enough space to do this). Checked everything, all flowed fine now. The customer was well happy as all he was left with just a small section of the boxing to retile and half a days pay to me, other plumbers had suggested he remodel the bathroom moving the toilet next to the soil stack and the shower to where the toilet is which would have cost quite a bit. Although the customer had done the tiling a local plumber had done the pipework and waste for the shower.

 

[chris watkins]

Strap-on bosses with rubber adaptors ------- YUK !!!!! Give me a S/W boss pipe every day:smile5:.
Well done Mick & Tamz, sorted.

 

[johnnyplumb]

Strap-on bosses with rubber adaptors ------- YUK !!!!! Give me a S/W boss pipe every day:smile5:.
Well done Mick & Tamz, sorted.

not the arrows that's the problem, it's the indian.

mark the depth of the slip on the pipe, insert the pipe to this mark only,
secure the pipe properly and it aint moving.

 

[chris watkins]

not the arrows that's the problem, it's the indian.

mark the depth of the slip on the pipe, insert the pipe to this mark only,
secure the pipe properly and it aint moving.

um still not convinced, far to many dangers, rubber bosses poping out under pressure etc etc
There is a horse tied up outside do you think it belongs to the arrows ???