advice please regarding WC

[adrianowlett]

We are refitting a very small bathroom and have an issue about installing the wc. The position of the new wc will be about one and a half yards from the original salt glazed downpipe. The floor is concrete and is not feasable to cut out a new position for the downpipe.

Is it possible/acceptable to use 100mm pipe FROM the horizontal stub on the new wc so that it flows at the appropriate angle direct to the old downpipe without using any supplemental pumping (macerator etc). Will the syphon pressure be enough to adequately discharge the waste without it "stopping" in the pipe.

I guess this is all pretty easy stuff to those in the know, but we don't, so can anyone help please??

 

[Softus]

Completely feasible. You just need to ensure that the fall between pan outlet and entry into the hole in the floor is correct.

"Correct", in this context, is 2.5 degrees, or, put another way, about 2.5 inches over a distance of 1.5 yards.

 

[adrianowlett]

Thanks for that. One further question if you can please. The angle of 2.5 degrees I assume is the minimum permissible and that a steeper angle would therefore be even "better". Is this correct?

 

[Softus]

Within reason, yes, but be aware that the angle is by design, and is such that solids would be washed away by fluids rather than the latter rushing past, so it would be possible for the angle to be too great.

I've just checked my figures (against ones supplied by Marley Plumbing & Drainage) on a 110mm branch soil pipe. For a flow rate of up to 2.5 litres/second their recommendation is 9mm/metre, so I've got something wrong somewhere.

Just rushing out, so will have to get back to you later...