Ready to hire?

Post your job in minutes, browse real reviews and choose who to speak to.Post a job

Need some tips or advice?

Plumbing

2 Toilets connected to one horizontal waste pipe

Anonymous user 30/05/2025 - 1.02 PM

We are renovating the family bathroom and have changed the layout. In the new design, the toilet position has been relocated, and we connected it to the existing soil pipe using a Tee fitting in the elbow to extend the pipe. T position is sideways as it is directly connected to the elbow and existing toilet. Although we haven't installed the new toilet yet, we tested the setup by flushing coloured water through the new toilet pipe. I discovered that this water flows back into the existing toilet through its built-in S trap. Can someone suggest how we can resolve this issue?

Are you a tradesperson and able to answer this question?

1 Answer

WK Handyman Services

No reviews yet

Doncaster

Instead of a regular tee, try using a swept tee instead to direct the flow towards the soil stack. Using a regular tee could well be splitting off and running too the other toilet. Soil and waste pipes rely on gravity to work correctly, another issue could be the slope on the pipe is not quite enough causing waste to run upstream. There are other options too explore such as adding in one way valves although not recommended for long term use. Also bear in mind the slope on the soil pipe should measure at a minimum of 1:40 for gravity flow. If none of the above work calling out a plumber would be an ideal option as there could be other things to consider such as ventilation etc that a licensed plumber could easily deal with for you.

Answered2 June 2025