40mm waste capacity

[razoray2006]

Hi Guys,

A month ago I installed installed a double power shower (2 showers in one enclosure). I have used 40mm waste pipe which is "T"d from the wash basin also 40mm from the trap. From where the waste joins the waste there is one 90degree elbow and then a straight run of 2.5-3m till the soil pipe.
The problem is when the showers are used the in coming water seems to be greater than the outgoing water hence the tray slowly fills up.

My question is this is the 40mm pipe adequate or should I have used something a little bigger or do you think the system needs flushing as there could be hair and gunk accumulating.

Thanks for any help
Ray

 

[Bahco]

I would try a 50 mm unshared waste pipe first. I would also check all the other pipes for any blockages too while you are at it.

 

[Richard C]

You could try flushing first but 3m is the limit for a 40mm unvented waste branch; although you may well find it’s venting through the basin tee by drawing the trap ! Add in the possibility of an insufficient fall gradient & that 90 degree elbow (bend is much better) on flow & that you could be dumping up to 14 litres/minute or more into the tray will give you an idea of what it’s trying to cope with. The type of trap you have fitted will also affect things.

A separate 40mm run with a good fall may just cope at 3m but I would go for 50mm as Bacho; again, use separate run to the stack to avoid problems.