Re-arranging kitchen sink P-trap to obtain more clearance in undersink cupboard

[bevanweiss]

Hi,

I've recently bought a new apartment, and the undersink drainage layout is currently quite obtrusive.

I'm hoping that there might be some ideas of how I could (get this) re-arranged to free up some more available space in the front of the cabinet.

The main obstruction is the location of the P-trap, and how far forward it is.  I would ideally like to have a 90deg bend immediately after the sink to at least push this back further.  Is this possible?

The standpipe in the back I believe is for the AC drain. The pipe section extending behind the sink is just a capped length (unsure what purpose it serves).

I'd be very interested to know what the most compact arrangement for these services could be (if the AC, sink and outgoing drain still remain where they are).

Thanks for any ideas / advise.  I'm pretty sure it will require a licenced plumber to perform the actual work, but I'd like to have an idea of what's possible, and get some good ideas before engaging one.

Bevan

[TedBear]

Yes, it is possible to move the P trap to the back. I have a unit from Ikea which has drawers immediately under the sink, so there is no room for a P trap there. The sink came with pipes that do exactly as you suggest.... there is a right angle attachment to the sink outlet which directs the water to the back of the cabinet and the P trap is back there out of the way.   And it all works fine. 

I think the "standard" connection, as you have, is only done because plumbers don't care about the end user's situation, (an almost useless cupboard) just their own quick and easy installation.

Because the connection into the drainage system already exists, you could do the changes to the pipe arrangements yourself, as long as you end up with the same ends ... i.e. a P trap to stop smells rising up, the water running away quickly (correct size pipes) and no leaks (connectors, adapters and glue).

(I am curious about the pipes at the back that don't appear to even have a P trap..?  But that's another issue.)

[bevanweiss]

The pipe at the back on the left for the AC drain uses a 'waterless valve'/self-sealing valve (https://www.hep2o.com.au/hepvo/) which does seem specifically intended for such installations on condensate drains.  It seems like it would be nice to use on the normal drain also, but I suspect this isn't allowed (if someone could advise which clause prevents its use for the kitchen sink/dishwasher drain it would be ideal.. I've looked through AS3500.2 but can't see where it would be disallowed).

The drain pipe that continues up on the right I believe possibly goes to an AAV (air acceptance valve) as a group vent (I haven't put my head all the way back there yet, I did feel around with my hand, and it just felt like a plain cap.. I'll check it tomorrow for sure).

Perhaps someone is much better at tetris than me, and can visualise a significantly better layout that would really optimise the remaining space?  I'm wanting to put the Ikea slide out rubbish/recycling bin unit in the front, and in an ideal world would also love to fit a water filter and Zip/Billi chilled water / sparkling water unit in their also..

EDIT: Ahh, I see the reason that the self-sealing valve couldn't be used elsewhere.  It can only handle low temperatures (<80degC) and can't accept drain cleaning fluids (or likely many other non-water fluids).

[EricL]

Hello @bevanweiss,

Welcome to the Bunnings Workshop community. Thank you for joining us and sharing your plumbing question.

I totally agree with @ TedBear it is possible to move the waste all the way to the back. It is an involved task and there are many components to be changed.

In these situations, I suggest considering what you want to put into the cabinet. Do you want to put a slide-out bin, some new shelves, or a pull-out basket? These items require a certain amount of space for them to fit in.

Once you've decided what you want to put in, you can then draw a plan of how you want the parts to be moved. Drawing sketches will flesh out your idea and give the plumber a possible course of action. I suggest visiting your local store to see the parts and get more ideas of how you can move your plumbing. 

If you need more information please let us know.

Eric

[bevanweiss]

Any recommendations for a good 3d layout software package for this kind of thing?

Being able to just drag/drop the various items around in virtual space would be nice.

Otherwise I guess I'll just model something up in Blender.

[EricL]

Hi @bevanweiss,

I personally use Sketchup but it has no pre-existing models to just drag and drop. My colleague MitchellMc uses Tinkercad for his illustrations and they have existing basic shapes that you could modify to use. I'm old school and usually use pen and paper when I generate my ideas before I commit them to Sketchup. I've not used Blender myself but I know it is a powerful tool for generating 3D diagrams.

If you need more information please let me know.

Eric