Is the kitchen waste outlet pipe too high?

Luke watson · 3 Aug 2020

Hi,
I've just moved onto a new place and the wager drainage is very slow. Underneath the sink, it looks like the water has to push a lot of water above it to get out. It goes down from the sink, then into a u bend before going upwards through a flexible pipe to the outside. Is this too far to travel against gravity...?
Thanks
Luke

oldbuffer · 4 Aug 2020

1. It isn't right. As you say, the water has an uphill struggle to get away.
2. However, the base of the sink and its outlet are above the through the wall drain pipe. Assuming that pipe then runs downhill, the sink should drain.
3. However, with all the connections, wrong direction and flexible pipe, it may well be partly blocked, and, even if clear, slow to drain.
4. I'd recommend you replace it all with McAlpine components, re-drilling the wall if necessary to get the correct falls.

oldbutnotdead · 4 Aug 2020

Whats connected to the waste pipe coming in top left of the pic?
That whole setup looks like it was chucked in on a Friday afternoon using whatever was on the van...it will be slowing the drainage and if it isn't blocked it soon will be. Take it all apart and redo it as simply as possibe

Madrab · 4 Aug 2020

All that pipework, up to the outflow will be left full of water, it will drain but it certainly isn't correct. It isn't designed to hold water like that and the seals and connections may leak over time. It will also start to smell. That's a really bad DIY job ( I hope)

The outflow through the wall needs dropped and then the trap arrangement sorted properly.

Luke watson · 4 Aug 2020

Thanks everyone, hugely helpful. I bought a McAlpine kit this afternoon so will look to clean it up over the weekend.

oldbutnotdead, the pipe in the top left of the pic is coming from the half bowl of the one and a half bowl sink.

PS I don't think it was a DIY job, but I might be wrong.

oldbutnotdead · 5 Aug 2020

Arr. Toolstation do a telescopic twin bowl sink drain thing (not sure if McAlpine do) with a shallow trap and a spigot for dishwasher/whatever.

Madrab · 5 Aug 2020

Luke watson said:
I bought a McAlpine ki

The one you have is a McAlpine double bowl kit (SSK2) by the looks of it. I must say though that I don't think it's the trap kit that's the issue.

By the looks of it the sink setup has changed from an old higher single sink setup with a straight P trap to a modern 11/2 (2) bowl sink and the multi waste. The arrangement and height would be completely different and therefore the outflow is now too high.

Without seeing more if it, it's hard to be sure but it looks like the only way it's going to work properly is to cut a new waste outflow through the wall.

Luke watson · 5 Aug 2020

Indeed, thay seems to be the case. I have installed the Mcalpine, but you're right, it hasn't done much to the height difference. At least the pipes are clean for the time being (they were very gunked up), but the waste pipe will need lowering in due course.

I'm surprised there isn't a trap that works from an old single sink set up to a modern one. Maybe there is, I just haven't found it. The trap could be beneath the lower main sink with the half sink feeding into it. It would need the tube from the half sink going straight into the U bend pipe rather than above, but maybe that is a bad idea for other reasons.

Madrab · 5 Aug 2020

Luke watson said:
I'm surprised there isn't a trap that works from an old single sink set up to a modern one

All depends on what was in before really. The outlfow through the wall would have been cut to take the original waste setup. Invariably the old sink were in purpose built kitchen units and tended to be higher, that and the trap setup was different.

Modern 11/2 bowl sinks and their wastes tend to be lower/deeper, ergo it doesn't work. That why I suggest it was DIY, that and the uphill flexi, probably the worst way it could be setup TBH. Usual would be to cut a new hole for the outflow and use the core to fill the old hole and just remake the waste run.

Madrab · 5 Aug 2020

In saying that, looking at the pic I must say I've seen worse but the trap and associated pipework will be full of water up to the level of the outflow, not good and needs sorted.

oldbutnotdead · 5 Aug 2020

You've got it much neater than it was but there'll still be alot of standing water in there above the trap which might hum a bit.
Can't find the one i used, this looks like the closest match https://www.toolstation.com/espace-extra-flat-sink-trap-1-12/p54424

Madrab · 6 Aug 2020

If I'm totally honest I wouldn't ever recommend using any other trap than a P trap under a sink. Some of the larger bottle traps can be used but they need regularly serviced to keep them clean. Anything else and it's just a blockage waiting to happen IMO.

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Is the kitchen waste outlet pipe too high?

Luke watson

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