replacing 6inch soil to 4inch soil

[mscg]

are there restictions when using 4in soil pipe I would like to reduce the diameter from the wc as I have to route the soil pipe under the bath and out through the wall - total run will be 5m with 1 90 bend

 

[JohnD]

what's the old pipe made of?

 

[mscg]

its just push fit plastic. Ive actually got to connect to a Giberit concealed pan and the giberet fittings are 4 inch away from the pan

 

[JohnD]

OK, I wondered if it was a clay collar, because the modern ones I've used are all 4-inch, so I was surprised you have a 6-inch.

What is the 6-inch part you have to connect to?

 

[mscg]

yes its going into a 6inch soil stack again plastic. so its 2metres under the bath through the external wall a 90 then 2 more metres before dropping into the stack. My concern is likelyhood of blocking or is 4 inch perfectlly acceptable? I presume I could reduce off the 6 inch stack to 4inch a the swept t

 

[mscg]

when I say 6 inch I mean 110mm and 4 inch 82mm !

 

[JohnD]

you've lost me now.

4" (110mm) is the normal size for UK soil pipe.

Have you got an American loo or something?

 

[mscg]

thanks for your help - I stick with the 110 mm - whats the 82mm used for then?

 

[JohnD]

might be for a rainwater downpipe?

 

[mscg]

ok thanks again

 

[Hugh Jaleak]

82mm is sometimes used for dry sections of a stack, i.e. vent. I was told at college pans are available with a 3" outlet, for connection to 82mm pipes, but have never seen it in practice. Soil pipe sizes are:

82mm=3"
110mm=4"
160mm=6"

 

[JohnD]

3" WCs are I understand used in the US, and occasionally appear on sale here, but I didn't know they were permitted on our plumbing system. I would have thought them more likely to block.

 

[Hugh Jaleak]

I think thats why they're not used! College was 20 years ago, legislation could well have changed since... I certainly wouldnt install a pan on a 3" pipe. Bad enough when 4" blocks!!!!

 

[Nige F]

I think thats why they're not used! College was 20 years ago, legislation could well have changed since... I certainly wouldnt install a pan on a 3" pipe. Bad enough when 4" blocks!!!!

I`ve seen 3" soil working fine @ an old house but it was lead and had vents etc. and done by craftsmen Was repairing a 2 1/2 gallon Cistern on the ancient syphonic WC - so asked about the small pipework ...Never had any bother . They didn`t like paying so maybe they were tight ar sed