Help with Kitchen sink plumbing

[Danm1les]

Hoping someone might be able to help

Colleague has just moved into his first flat and has a problem with the kitchen sink, when running the dishwasher or washing machine the sink is backing up and then taking an age to drain. He said only one is run at a time and it looks like the pipe going backwards towards the wall after the trap has a slight incline.

Is there anything that can be done to remove the incline in the pipework? Something like this?

https://www.screwfix.com/p/mcalpine-t12a-2-bsp-str...

[Lotobear]

....first thing to do is check the trap for accumulated crud - there's usually stuff in there that resembles the primordial soup.

[craigthecoupe]

If its a new place I'd probably undo the u bend and check it's not blocked. when reinstalling, often, the fittings allow for some adjustment, I expect the pipe below the Y can be slid up a cm or two inside the other, then tightened up with the threaded clamp.

[Danm1les]

Lotobear said:

....first thing to do is check the trap for accumulated crud - there's usually stuff in there that resembles the primordial soup.

I mentioned that too him and he said he has had the trap off and its all clear.

[Danm1les]

craigthecoupe said:

If its a new place I'd probably undo the u bend and check it's not blocked. when reinstalling, often, the fittings allow for some adjustment, I expect the pipe below the Y can be slid up a cm or two inside the other, then tightened up with the threaded clamp.

I did think that as it looks like a 2 pipes slipped over the top of each other?

[craigthecoupe]

Danm1les said:

I did think that as it looks like a 2 pipes slipped over the top of each other?

looks that way, on the left of the u bend, the pipe slips over the other. looks like theres 10-15cm of adjustment. it doesn't need to be a steep fall, just not inclined ideally. that said, I'm still leaning towards a blockage somewhere..

[rodericb]

Chuck heaps of drain cleaner down it and some buckets of hot water. If you've ever watched drain cleaning videos on youtube they can get blocked up with grease and fat. If the previous occupants tipped oil down the sink and washed their clothes with cold water it could promote the creation of fatty sludge.

[shtu]

As above, it looks like the trap could be moved upwards a little to add some fall to that horizontal section. It also looks like turning the trap would allow that section to be several inches shorter, which should also help a bit.

Soda crystals and boiling water are a good combination to clear drains without too many nasty chemicals.

Edited by shtu on Monday 22 September 16:15

[craigthecoupe]

Yep, better to start with a couple of kettles of hot water down the sink, let that sit for 10 mins, then another one and plunge. Saves pouring more st into the water courses, no harm in trying that first.

[Russet Grange]

I'd check outside as well if accessible. Unless the pipe is solvent weld he should be able to disconnect and check that water flows freely down to the drain. Should be fine but a very easy thing to try.

[OutInTheShed]

I think those appliance hoses should loop higher above where they join the sink drain, to reduce one appliance filling the other.
Maybe loop them right up and cross them over?

If the sink drains slowly, there is gunge in the pipe work, end of !!!

Personally I would re-do the whole thing so the sink WM and DW don't (cannot!) drain into one another.
You've probably got a disgusting cocktail of food waste, soap crud and dishwasher chemicals swilling around.

A dose of thick bleach down the sink every day for a week often does the trick, but you want it going down the drain route not into the DW or WM.

You could disconnect the appliances, block those ports then give it what for with a good old sink plunger,

[TVR Sagaris]

Do the bathroom basin and bath drain OK?

[Djtemeka]

That incline will do bugggerall to stop the water as it’s such a short run then drops down.

Remove the whole u bend then clean out that bit of straight pipe.

Before doing this, that whole plumbing system probably holds 3/4l of water.

Run that amount of water down first. If the water only reaches the sink waste and then comes up AFTER that amount of water then the blockage is further down than the plumbing inside the cabinet.

[Djtemeka]

You may be able to plunge it but get a second pair of hands in to block off the overflow hole whilst you plunge it or the plunger won’t do anything.
You need suction on a closed system. The overflow hole negates that.