So, I'm fitting Jen's new kitchen, which is something I've never done before, and I've got a question.

I've got to fit the sink. Now, I'm happy with cutting the hole in the worktop, and the plumber was kind enough to leave me with enough hot and cold copper pipe sticking up that I can just attach the taps with some bendy connectors (the ones with the steel braid over them that screw into the bottom of the tap fitting).

I've got a question about the waste pipe. Again, the plumber left me a suitable place to connect to the waste pipe in the building trunk, but I've got to get there from the sink.

When I attach the waste trap (it's a bottle-shaped one) to the bottom of the sink, the waste port is going to be about 6 to 9 inches above the pipe that I've got to connect to, so I can't just run a piece of horizontal pipe. I need to cover about 30 inches horizontally, as well.

So, can I simply add a section of pipe between the sink and the waste trap, to lower the trap to the right level, and then run straight across (forming a right-angle)?

Or should I fit the trap directly to the sink and then use a pair of 45-degree joins so as to run the waste pipe down at a more leisurely angle?

Or something else?

This is all working in 40mm plastic pipe, BTW.

Greetings!

UGH! You never want to have flat horizontal runs or 90 degree angles. That will be horrible to maintain, because you need a slight pitch to help the water drain. Something that level will get stuff clogged in it very quickly.

Do you need to put an S or P trap in there? A P trap might give you the right distance, and you can set it an enough of an angle to have it drain properly. Either that, or a 45 at the sink, a 45 at the waste pipe, and a straight run between the two. I think you are better off with a trap, though, unless there is one that you can clean / access at the sink itself.

Electricity, I know, but when faced with a plumbing situation like yours, I zoom down to B&Q and stalk round 'till I see one of those older employees they are so rightly proud of and pounce: Those old guys know everything - one of them slashed the cost of my study work surface by two thirds with the one piece of lateral thinking.
To quote Harry Enfield: You don't want to do that, you want to do this! and they're generally right.

- I assure you that I have no connection with B & Q -

You might find something here, if you can't get to the store!

No technical reason that i can think of for not dropping the waste trap other then taking up loads of room

perfect solution is to take the waste pipe along the wall if possible with out a clearer picture it is hard to say.

If putting up Wall units a good way is to put a batten along the wall at the hieght of the bottom of the wall units and then sit them on that and then fix them back to the wall Rather then some of the crappy solutions that come with sme wall units.

I zoom down to B&Q

Yeah, I'm probably their best customer this week.

Do you need to put an S or P trap in there?

I don't believe so. The sink kit requires a bottle trap

This forms a right-angle under the sink, but I've then got to drop that horizontal pipe down to another horizontal pipe.

or a 45 at the sink, a 45 at the waste pipe, and a straight run between the two.

That's probably what I'll opt for.

with out a clearer picture it is hard to say.

I've put a photo on my website.

You can see where the taps are going to be connected using the flexible hose (the two vertical copper pipes). The bottom of the sink will be about here (maybe a little higher and to the right). The bottle trap will sit about here.

On the right of the picture, you can see the waste pipe. It's got the waste hose for the washing machine on a non-return valve coming out of the top.

The short tube with the plastic bags stuffed into it is just to cap the waste pipe until I've connected it to the sink.

The blue and red hoses coming off the uprights are going to the washing machine (out of shot on the right).

Underneath the pipes on the right is the gas meter, which is one of the things making this kitchen so tricky to fit.

If putting up Wall units a good way is to put a batten along the wall at the hieght of the bottom of the wall units and then sit them on that and then fix them back to the wall

Yeah, that's what we've done with the wall units that are currently up. My stepdad and I did those at the weekend. (Picture in the same place)

With North American plumbing standards, your "horizontal" pipe must slope towards the drain at a rate of 0.25" vertical per 12" of horizontal. Any more, or any less, is unacceptable (for different reasons). The total vertical drop during the horizontal run must be less than the inside diameter of the pipe used, so that there is always an air escape route above the flowing liquid, to keep it from sucking the drain trap dry via vacuum.

A vertical drop from the sink to the trap is fine for short distances. Dunno what "short" is defined as, but 10-20cm should be no issue.

Cheers

The trap has always to be immediately under the sink, I'm reliably told by my normal drinking circle (Kronenberg, Woodpecker, Red Stripe, Extra Cold x 2, Diet Coke), the extension can then be as you suggest.
You'll have to wait until 1.00p.m. tomorrow for the definitive boiler answer- no, wait a minute, it's eat as much as you like, curry buffet day, tomorrow.