Best way of running kitchen waste pipes?

Looking for some advice on re-routing the kitchen waste pipes.

Piccy here:

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the sink, dishwasher and washing machine all disappear under the floorboards individually (the DW and WM via upstands) and merge under the floorboards somewhere into one 40mm pipe that emerges outside just above the drain. Not sure what sort of connection has been used but periodically we do get a nice stink of drains.

I was planning to connect the DW to the sink trap via a spigot. The WM is staying where it is as I can't see an alternative to running this pipe under the floorboards as the back door is between it and the drain.

But what would be the preferred solution for running the pipe from the sink to the drain? Is it better to have three meters of pipe on the exterior wall (unsightly but easier access, decent slope), or behind the units (hidden but inaccessible, decent slope) or under the floorboards (hidden, inaccessible, shallower slope)?

How best to connect the sink and WM runs? And do they need additional venting?

I've always used push fit in the past but is solvent weld a better option? And do I need to increase the size of the pipe to 50mm?

Thanks in advance for any advice.

Reply to
mike
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Sounds like you have not got traps on all the pipes...

(its better to have one trap per appliance rather than a shared one later on since there is less chance of overloading the trap, and you don't have too many feet of open pipe to potentially smell.

Never been keen on them - or at least the type that empty above the sink trap - you tend to get a rushing water noise out of the sink plug hole.

OK, but add a trap at the bottom of its stand pipe before it vanishes into the floor.

The last one does not sound particularly attractive. The first is easier to maintain but less pretty. You choose! ;-)

No additional venting is required since both are vented at the origin. One would usually join the other via a swept tee.

Either are fine. Push fit allows easier disassembly should you need it, but you need to be a little careful clearing blockages with rods etc on unaccessable push fit, since you don't want to pop a fitting off where it would be hard to get at. Personally I use solvent weld mostly these days for anything that will become inaccessible - but include rodding eyes at strategic locations just in case.

Reply to
John Rumm

We had exactly the same situation, several pipes (dishwasher, washing machine, sink) joined under the floor and then existed at the front of the house. We got a smell of drains from time to time. Eventually I looked under the floor (not easy) and found one joint had come apart slightly and large lake had formed on the concrete under the house. There was a fine layer of fluffy hairy stuff growing all over it :-(

Robert

Reply to
RobertL

Not quite the scenario I had in mind... I was just talking about the lack of a water trap on a dishwasher pipe means you have an open pipe between the back of the machine, and the air space a couple of inches above a drain gully.

(but what you describe is one reason for using solvent weld when out of sight!)

Reply to
John Rumm

John,

Thanks for the reply.

Is there a recommended slope for this kind of pipework and is there any need to upgrade to 50mm?

Reply to
mike

Great. I'm looking forward to finding something like that. ;-)

Reply to
mike

IIRC something like 1 in 40 - its in the building regs doc on drainage...

Not really. I have used two stand pipes and a sink all merging into one

40mm outlet and not had a problem.
Reply to
John Rumm

Thanks. Thought it would be too trivial to be part of bulding regs and would just be a matter of convention. Guess I should have know better...

Reply to
mike

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