Connecting sink drain to WC soil pipe

[Joe Kelleher]

I recently moved into my first home, which has a toilet but no sink in a small room downstairs at the front of the house. I want to add a sink to the downstairs toilet, but I'm unsure of where and how to connect the drain outlet. The soil pipe from the toilet does not go through the front wall, but rather turns downwards into a concrete floor. There is no drain pipe or vent outside at this point. Is it acceptable to feed the waste pipe from the sink directly into the outlet of the toilet somehow? The sink is only about 1 m from the toilet. Does anything need to be done to prevent backflow of sewage or foul vapour to the sink? Would it help if I installed a vent to the outside, which is presumably possible using small diameter pipe?

Thanks,

Joe

[OldBill]

You can get a clamp on boss that goes round the soil pipe. If the soil pipe is plastic its easy to drill the required hole in it, harder if its cast iron. Of course, this goes after the U bend of the toilet and you have a U trap or Hepworth valve in the basin waste pipe to stop smells. Modern soil systems are sealed so you don't want to add any venting/

[John Rumm]

You may be able to change the WC connector to one that includes a pipe connection point. Have a look at product number WC-CON8V on

example.