Plumbing in a sink waste to a soil stack

[str]

I have a downstairs W.C. without a wash hand basin so am looking to remedy this situation.

The existing W.C. is to be replaced with something more modern, so it looks as though the plastic soli pipe will need altered before it joins the main cast iron soil pipe from the upstairs bathroom.

Is it okay to to tie in the sink waste into the soil pipe for the W.C. before the soil pipe is tied into the main stack?

cheers

 

[swidders]

It has been done - but care needs to be taken to ensure that flushing the WC doesn't cause the sink trap to empty due to negative pressure.

 

[badgerchief]

It has been done - but care needs to be taken to ensure that flushing the WC doesn't cause the sink trap to empty due to negative pressure.

if you have the problem of negetive pressure as i have done in the past fitting an air admittance valve will solve the problem however the valve to my knowledge needs to be fitted inside the property available from screwfix.co.uk quote 42968

 

[swidders]

the valve to my knowledge needs to be fitted inside the property available from screwfix.co.uk quote 42968

looks about right

 

[longdogs]

Fit a 32mm non return valve in the basin waste pipe work close to the soil pipe. This will prevent any s**t travelling back up the pipe if there is a blockage.

 

[str]

thanks for the prompt responses

Is this a job a reasonably compentent diyer can do? I will have a plumber on site doing other jobs soon so may try and get a steer if he has a look at the current setup

 

[swidders]

It's all pretty basic plastic pipework so should be within your comfort zone

 

[str]

I thought that it should be within my skill base

my only concern was that the main soil pipe from upstairs is cast, but it already has plastic tied into it, so I guess I should be able to reuse that connection?