Plumbing washing machine waste to bath

[proftanda]

Hello,

I'm hoping to turn the cupboard next to my bathroom into a utility room for my washing machine.

The basin in the bathroom is mounted on the far wall from the cupboard with a pretty chrome bottle trap so I was hoping to plumb the waste from the washing machine to the bath instead - the bath is along the wall adjacent to the cupboard and the waste pipe is hidden behind a bath panel.

Would it be possible to just run a waste hose to the bath waste using a y connector to fit it before the bath trap? I've read in one place that the trap needs to be above the level of the washing machine drum.

Thanks!

Nick

 

[Hugh Jaleak]

Drain hose for the machine must be above the level of the drum or the machine will never retain any water! Dropping the hose below the level of the drum allows the water to drain from the machine by gravity, this is the emergency procedure for when the machine has broken down and you've got a drum full of water and wet clothes!

You'll need to hook the drain hose into a standpipe with a trap, and take the waste from this to a suitable point. I suspect it would be better run independently to the drain, connecting to the bath may result in the water pumped out the machine reappearing in the bath before draining away....

Basin waste is too small to connect a washing machine, basins use 32mm diameter waste, a washing machine needs a 40mm diameter waste.

 

[longdogs]

If possible, fit a 40mm non return valve between the bath trap and the new connection

 

[proftanda]

Hi Hugh. Thanks for your reply.

A standpipe and trap next to the washing machine should be fine as there's plenty of room.

However, I live upstairs in a block of flats and neither the cupboard or bathroom have an external wall so running to a separate drain would be tricky.

The bath waste goes through the wall to void between me and my neighbours flat. I think this is where the common waste pipe for all the flats goes down through the building. There's no access to this from my flat.

Is there a way to check whether the waste from the washing machine would back up into the bath without actually cutting into the bath waste? Or a way of connecting it to minimise this?

It's also a hefty copper (imperial?) pipe - see pic. What would I need to connect a plastic waste?

Thanks again!

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[Madrab]

Pic link not quite right, here you go

- View media item 90287

 

[proftanda]

If possible, fit a 40mm non return valve between the bath trap and the new connection

Hi squeaky - is this to stop back flow into the bath?

 

[Hugh Jaleak]

Hmmm, that might be 1 1/4" (32mm)dia, not ideal as washing machine needs 1 1/2" (40mm) diameter waste, but given circumstances you have limited options. You can connect to it using compression waste of the appropriate size, and you ideally could do with a non return valve between the washing machine connection and the bath as squeaky suggests, otherwise I can see the discharge from the washing machine erupting in the bath....

However, room is going to be limited, and you may not get a NRV in the gap left, and also with the machine emptying into the smaller pipe, allow the bath to fill slightly when the machine empties, (for a few seconds until the water finds its own level again). Although far from ideal, would be infinitely better than an overflow elsewhere if the machine is discharging faster than the water can drain away.....

 

[Madrab]

The other thing you may need to watch for, if that pipe isn't wide enough (=>1 1/2"), then you may get syphoning of the bath trap when the machine empties, an in-line AAV may be needed if you find that happens.

 

[proftanda]

Thanks all for your help!

Yes - I've measured the bath waste and it's only 32mm.

I guess step 1 will be just to try it without the non-return valve to the bath and see if it flows back to the bath.

Fingers crossed!

 

[Madrab]

If you're going to use that as the drain then keep a loop or as much of the WM drain pipe up as high as possible to try to minimise induced syphonage, as others have mentioned.