Waste pipe diameter

[Richard Knight]

I'm in the process of installing new water supply and waste for a washing machine. All done except that I've discovered I need to run a new pipe through the wall to connect to an existing waste pipe. Not a problem until you realise the wall is 60cm / 2ft thick and made of stone. There is an existing hole I could take advantage of but that would mean running a narrower pipe than I 've run from the washing machine to this hole. Currently I'm using 40mm. Is there any reason why I couldn't simply use the next size down (whatever that is) to run through this existing hole and make my life a whole lot easier than either a) enlarging the hole or b) drilling a new one?

Thanks
Richard

 

[fido]

In UK the next size down would be 32mm but I don't know about France. This is still bigger than the drain hose coming from the machine so it should not be a problem. If you do have it overflowing from a standpipe arrangement you could plumb in a cone adapter onto which you would then plug the machine waste hose.

 

[bathjobby]

This is still bigger than the drain hose coming from the machine so it should not be a problem

Except that the machine is pumping it through the narrower pipe and once out of that your relying on gravity i.e. 15mm pumped vs 32mm gravity.
So a cone connector maybe better as that would let the machine pump into the 32mm, providing there isn't any other open low point in this pipe work were the water would surface before having chance to drain away.