New kitchen sink in slightly different location

[OldKettle]

Hi,
I need to replace a kitchen sink. The new sink needs to be re-sited slightly (so that the drain is about 100mm to the left). I also need to add a new fitting to accept a dishwasher, so had planned to use something like this.

I'm just wondering what is the easiest way to work around the fact that I need to move the drain. The old hole in the wall, that can be seen in the pictures is about 180mm to the left of the current pipe, centre to centre). Should I just use a flexible waste connector, something like this, or is there a better way?

Any thoughts would be much appreciated.

 

[Newboy]

Replace the lot with solvent weld fittings. Don't use the flexible connector - it will end up full of sludge.

 

[OldKettle]

Replace the lot with solvent weld fittings. Don't use the flexible connector - it will end up full of sludge.

Thanks. Would that include replacing the metal exit pipe, or is there a way to retain that? Can I just cut the metal pipe shorter and then two PVC elbows and a straight bit of PVC?

 

[Newboy]

If you're doing the job then it's worth doing it all. If you don't feel like replacing the old copper waste then a compression fitting will probably seal your new PVC/ABS waste pipework to the internal stub of copper.

 

[Madrab]

Use a compression elbow to attach to the copper pipe as it comes through the wall to turn the run left, then a small length of pipe to bring it inline with the new sink waste position, then into a solvent weld elbow to turn it left again to bring the pipe out towards the sink waste and then another small piece of pipe to the location of the new sink trap.

Ensure the copper is nice and clean before fitting into the compression elbow and ensure it's a nice tight fit.

 

[Hugh Jaleak]

You may find that copper waste pipe is 1 1/4", which isn't really big enough for a sink and dishwasher discharge, ideally needs to be 40mm or 1 1/2" diameter. It does look like there was a previous waste pipe going through the wall to the left of the current waste in the internal photo. If this hole is in a better position for the new installation, use a hammer and small chisel, and you'll soon remove that mortar filling from the outside. Inside looks to be stuffed with paper. Remove old waste and make good the old hole, and round the new waste with some mortar.


Alternatively if you'd rather keep the current pipework through the wall, Polypipe push fit waste will go onto copper pipe. Make sure the end of the copper is chamfered to remove any sharp burrs, the Polypipe fittings will be a tight fit but do go on.

 

[OldKettle]

Thanks for all of the advice.

If I am going to re-pipe everything, is it better to install a separate appliance trap, just something like this

Would that give a better result than one of the combined appliance/sink traps?

 

[John D v2.0]

Yes a separate trap will be better if you can fit it in. Less noisy and less chance of sink waste entering the dishwasher.

 

[OldKettle]

Thanks for all of the previous advice. It turns out that I need to move the sink further than originally anticipated, so I plan to drill a new 52mm hole and install a 40mm pipe.

I am also planning to install a sink S trap (in line with the new hole) and a separate appliance trap (such as the one I posted above), to the right.

I'll run some extra pipe to drop down from the sink S trap, meeting the appliance trap output at a tee just before it exits through the wall.

As the appliance trap outlet pipes seem to be installed lower, I intend to drill the new hole in the location marked with the duck tape in the picture below. The second picture shows where it will come out and run to the drain (as marked with the tape).

Do that all look ok? Any thought would be much appreciated, before I go ahead and start drilling

Apologies for the terrible drawing

 

[John D v2.0]

Looks good to me. Just make sure the open end of the pipe discharges properly into the gulley. Ideally below the grid to avoid leaves blocking it up but the main thing is not to splash around

 

[OldKettle]

Looks good to me. Just make sure the open end of the pipe discharges properly into the gulley. Ideally below the grid to avoid leaves blocking it up but the main thing is not to splash around

Thanks. Will do.

I read somewhere else that a P trap would be better than an S trap, due to the S trap being considered unvented. I thought that an S was a good idea as it lends itself to the vertical drop down to the tee.

Is an S ok or would it be better to have a P trap with a longer initial vertical drop and then just joining horizontally direct to the tee?

 

[John D v2.0]

Yes p traps are better because vertical pipes can fill 100% with water and siphon out the trap. I did wonder if emptying a sink load could pull the washing machine trap due to the fall on the pipe being too great, but it's a short run anyway. It's 32mm basin pipes that are bad for gurgling, the ensiute basin i just fitted i dropped directly into a50mm stack to avoid issues

 

[Madrab]

No Need for an S trap, just use a P trap off the sink and then ABS solvent weld, straight back to an elbow to drop down .... as suggested, less liable to self syphon.

 

[OldKettle]

No Need for an S trap, just use a P trap off the sink and then ABS solvent weld, straight back to an elbow to drop down .... as suggested, less liable to self syphon.

Thanks. Just to check my understanding, do you mean like this?

 

[Madrab]

Yep, that's the one.