2 pipe waste system

[Stephen Rice]

Hi,

I wonder if I could call upon the expertise of the group?

I have a tall house with a two pipe waste system. The bath and basin upstairs drain to a hopper which then goes down a 68mm plastic pipe down 2 (and a bit) floors (about 20 foot) to just below ground level where it doglegs through the wall of the cellar and then discharges into another hopper in the cellar and then continues from this hopper in 68mm plastic pipe to a drain in the floor of the cellar. The waste from a shower and basin also drain to this second hopper.

For many reasons, I would prefer not to have the second hopper: It is ugly where it is (ok the cellar isn't great but...); It gives off a certain not-that-pleasant smell; The cellar is dry and used for storage etc and I am worried that if a bath and shower all go empty at once that it might overflow.

Can I remove the second hopper and just join the lower shower output (from

40mm pipe) straight to the pipe as one would with a single pipe system?

If so what is the best way of connecting the 40mm pipe to the 68mm? (It doesn't seem to be a standard part! :)

Thanks very much in advance

Stephen

[Andy]

The only problem I can see is that if you empty out the upstairs bath or basin, that water might have a siphon effect on the downstairs shower and basin, i.e. the water from their u-bends might be sucked away when you use the upstairs bath/basin. This would allow smells to come up the plugholes of the downstairs shower/basin.

Of course it might not. I defer to more experienced hands. Onething to remember is that ater clings to the wall of a draipipe, so if siphoning did occur it might be possible to avoid it by careful arrangement of the shower/basin wastes as they feed ito the drainpipe.

I have no idea what the regulations say.

Andy.