Long waste trap to relocate washing machine

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Hi all, I'm a long time reader, first time poster. I've looked all over for a definitive answer on this but can't seem to find one.

I'm moving a washing machine from its current location near the soil stack on the ground floor to the other side of the room. The wall at the new location is separated from the wall where the soil stack is by doors, so I can't run a waste pipe all the way around and I'll have to go under the suspended wooden floor.

My question is, does anyone think it is acceptable to run a waste pipe from the new location under the floor for about 2m and then back up to join the old waste pipe that falls into the soil stack? The top of the pipe where the washing machine waste enters would be about 400mm above where the pipe would rejoin the old waste. I could optionally put a traditional trap above the floor before it goes under the floorboards, but it wouldn't be necessary and I probably won't. I'd use solvent weld joints and I reckon the trap created by this arrangement of pipes wouldn't hold more than 4kg of water in total (I'd support it at 0.5m intervals).

The new location isn't near any external drains so I can't drain it that way. The other option is to create a new falling waste under the floor over about 4m and cut into the soil stack below the floor. I have contacted the BCO and they said it would be fine for me to go ahead and make the new soil stack connection under the floor. However I'd rather not do that as it will make this connection very hard to access in the future. The long trap I'm suggesting will be accessible with only a few floorboards lifted.

I've added a diagram of the situation below. Any comments will be greatly appreciated.

View media item 14578
 
I love Plan A. It won't work, but full marks for originality.

A 50mm pipe under the floor into the soil is Plan B, and a lot more practical.
 
kevplumb: Thanks. Any idea where I can get a slow bend from? Is that a metallic connection you've shown or plastic like the rest of the waste pipe? Would a 92.5 degree connection be good enough? I'm guessing that a flexible connector isn't recommended.

Does anyone think that the strap on soil boss with a rubber insert is going to be a problem for connecting under the floor like this? Is there a solvent weld version that I could use instead, and would that be better?
 
you can get slow bends at any plumbers merchant yes plastic same as the pipe

they where just the first pics i found :wink:

personally id go for a strap boss

bit more support :idea:
 
Plumbcenter if you have one handy sell them as bends or elbows.

The reason is it will fill up with sludge and shi? and block up in a few weeks of use.
 
I'll seek out the slow bend, I think I know a local supplier who will stock it.

Referring to the strap on boss joint (where the waste pipe meets the strap on part, not where the strap on part meets the soil stack), are there two types of these: one where a rubber insert makes the seal and another where it is solvent welded like everywhere else? Or is there only the rubber insert type? I'm really looking for the most reliable thing I can get when I'm going to floor over it.

Thanks for your help everyone.
 
SP 318 from screwfix will do the job,although it requires a rubber insert reducer, (not sure if you can get a solvent insert from screwfix) better to get something similar from plumbers merchant in solvent to 40mm
 

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