New washing machine plumbing

[AnotherGreg]

Hi

I am in the middle of planning new plumbing into the conservatory where I'd like to put my washing machine.

The house has got switchback stairs with a downstairs WC underneath the taller part of the stairs. Under the rest of the stairs including the middle landing is just a waste of space which you can only access by lifting part of that landing.

Under the stairs, you can see the back wall of the downstairs WC - just a bit of plasterboard - and the toilet is against this wall. I have cut through part of the plasterboard and can see the cold water to the cistern and the waste pipe (this is all boxed in in the bathroom, so there isn't now a big hole in the wall!).

I will hopefully put a tee in the cistern feed and branch off, under the stairs and out the back wall (less than a 2m length). My problem, however, is the waste.

The waste comes out the back of the toilet, 90° horizontal turn, a short horizontal length and another 90° turn and then about 2m horizontal pipe into the main waste (it's all boxed in). Can I... boss into the toilet waste that I can see through the section of plasterboard I have cut away and connect the washing machine waste into that? Is that allowable, or will washing machine waste start to come up through the toilet?!

Sorry this is long - I hope I have been able to paint a reasonable picture in your mind! Thank you in advance for all your help.

 

[longdogs]

Is it not possible to connect to the 'main' waste pipe?

 

[AnotherGreg]

Hi Squeaky, thanks for your reply. I suppose I'm just trying to save myself some time and having to unbox the pipework in the bathroom to get to the main pipe.

And then the waste length would be over the 3m branch limit - for 40mm pipe anyway. So not sure how to go about that.

 

[longdogs]

Can't really see a problem with going into the horizontal part of the pipe (into the top of the pipe) using a strap on boss, perhaps as far away as possible from the wc. Hopefully the 'fall' in the pipe would prevent any water travelling back into the toilet pan. Obviously you would need a trap in the w/m waste and maybe worth fit a non-return valve in the w/m waste to prevent toilet waste going up it if the drains ever get blocked

 

[AnotherGreg]

Thank you so much for your good advice, Squeaky. Your time in reading my question and answering is much appreciated.

 

[Nige F]

Can't really see a problem with going into the horizontal part of the pipe (into the top of the pipe) using a strap on boss, perhaps as far away as possible from the wc. Hopefully the 'fall' in the pipe would prevent any water travelling back into the toilet pan. Obviously you would need a trap in the w/m waste and maybe worth fit a non-return valve in the w/m waste to prevent toilet waste going up it if the drains ever get blocked

Use a Hep V O waste valve instead of trap