Washing machine waste - size issue

[Pickup]

Hi,

I'm trying to plumb in a washing machine however because of the kitchen layout we have I am restricted for space.

The installation instructions for the washing machine indicate that the flexible hose (part of the washing machine) should not be extended and must be min 600mm above foor level.

The washing machine hose will reach a space where I can fit an 32mm upstand(?) and 32mm trap and from the trap run (about 1 metre of) 40mm waste pipe to connect to the existing 110mm soil pipe.

Searching through the forums I can see that 40mm is the recommended size for a washing machine waste but given the hose is only about 25mm diameter will 32mm be too small?

Thanks

Fraser

 

[imroberts]

The term you were looking for is "standpipe"

You'll find most standpipes are 40mm throughout and this would be recommended over a 32mm waste.

The reason as I understand it is that the waste is pumped out of the washing machine under quite a pressure, hence it doesn't need a huge pipe. When it reaches your standpipe and trap however, the flow will be comparatively limited as you're relying basically on gravity to drive away the water and therefore a much larger pipe is needed to prevent water backing up and out of the top of the standpipe.

I'd definitely stick with 40mm. You can pick up standpipes fairly cheaply from the likes of Screwfix:

http://www.screwfix.com/prods/18640/Plumbing/Wastes-and-Traps/Washing-Machine-Trap-40mm