solvent weld pipe fall?

[Fred]

Hi,

My kitchen refurb continues slowly. I have finished plastering and will post about that soon.

I ripped out all the old pipe work when I started so rightly or wrongly, now have to re plumb the dishwasher. If you remember I was asking about using solvent weld pipe.

I read the wiki:

and there is a paragraph about halfway down that says "New pipe work should have a fall of 18-90 mm/metre to comply with building dregs part H. Pipe work outside these figures has increased tendency to deposit solids, increasing risk of blockage. "

The range 18mm to 90mm is a big one; is it better to be nearer 18mm or

90mm fall per metre? Why aren't the regs more specific!?

I am unsure how to achieve these levels of fall. Fittings will only accept pipes at one angle. I thought they were at 92 degrees? Perhaps there is a slight margin in push fit and compression fittings but even so the wriggle room will not be that generous. How would you fit a pipe falling 90mm/m into a tee?

It doesn't help that the drain in my kitchen is offset, halfway between the sink and the dishwasher, so my plan was to use a tee to split it to the dishwasher on the one side and the sink on the other side. It is only 40mm but to upgrade it would involve digging down through a concrete floor, so if it's not broke, I figure don't fix it. I haven't had problems before with sink and dishwasher draining at the same time.

Can I also tee the boiler condensate drain into the same pipework or do I risk siphoning the trap in the boiler every time I empty the sink?

TIA

[Tim Watts]

On Sunday 02 June 2013 22:54 Fred wrote in uk.d-i-y:

As steep as possible. Faster flow is usally better with kitchen wastes. I have less than that with my bath waste (starts low down and travels a long way) but that does not suffer solidifying fats. I mae sure the kitchen waste that runs parallel has a much steeper slope - but then it starts much higher than a bath trap so that was easy.

You can engineer the fall with a bend in the X-Y plane (rotate it) but if for some reason, that is not possible, the best bet would be to include a universal coupler which will have usually enough slop to do the job.

Or you can heat the pipe with a hot air gun and very gently put a slight bend in it.

That's not a good design if you mean:

Dishwasher---------======-----------Sink || ||

. If you look at a waste tee, they are profiled to take flow from one end and side out the other end. The scheme above will see poor flows and lots of side to side overshooting. This would work:

=---------------Sink || Dish-------------==== || | |

Top is a 90 degree swept bend.

40mm is sufficient. 50mm is nicer if you have the luxury of a new install, but most houses use 40mm for such matters,

Pass - but it's possible an air admittence valve (small one, you can get

40-50mm universals ones - check Floplast) might be a good idea regardless - as the dishwasher trap may fight the sink trap WRT suction effects.

[Andrew Gabriel]

Dishwasher can probably pump around to the sink, and then enter the sink trap. (I use 21mm solvent-weld overflow pipe to carry it under the units in my kitchen, around to the sink trap.) One advantage of this is the hot detergent discharged by a dishwasher is excellent for keeping waste pipes clean.

I do that with a bathroom basin, but I use a U-trap with AAV on the basin, to ensure it doesn't suck the condensate trap dry.

[Fred]

Hello. You are quite right; the top arrangement is what was there previously but lie you, I was concerned about the tee being the wrong way round and I could not see how to get a slope into either end of it, which meant there was no/little fall towards it. I am installing using the second arrangement but cannot slope the pipes as much as I would like because the tee will only accept them at a certain angle and I think a 135 degree tee would be too steep. Your idea about the hot air gun sounds good. The wiki says non-compliant pipe work often works in practice but it would have to be compliant on new builds, so I wonder how they achieve this? Perhaps by not using tees in the first place!

[Fred]

I hadn't thought of that. Overflow pipe is no smaller than the outlet hose of the dishwasher so there shouldn't be any problems with that. How do you join them; with a jubilee clip?

That's what I will use if there is a problem. I suppose I might need two AAV; one on the sink trap and one on the dishwasher trap.

[Tim Watts]

On Friday 07 June 2013 09:47 Fred wrote in uk.d-i-y:

You don't need any significant slope on those short sections - virtually horizontal is good enough ove a few feet as the flow will be frequent and vigorous.

It's the main long run to the final drain connection or gulley that needs a slight slope as that's where crap tends to have time to settle out and the water cools, depositing fat solids.

HTH

Tim

[Phil]

There are tundishs (basically an air gap) for condensate drains.

[Andrew Gabriel]

Yes. I think the outlet hose's rubber end slid over the overflow pipe OK, secured by a jubilee clip.

Since then, I've done something similar with a washing machine, but discharging though 15mm copper. I soldered a 15-22mm adapter on the end, and the outlet hose's rubber end slid over that. (Actually, I removed the 15mm pipe-stop shoulder from the fitting, and soldered it on the pipe end the wrong way round, so I had the

15-22mm sloping shoulder to push the rubber end over.)

You only need one on the same side the condensate trap is teed in. It will work for both sides.

[Rick Hughes]

I have always set to 20mm per M, but many don't worry and as long as there is a fall then that is good enough. Toilet pan connection would be more critical, but angle there is set by connector normally.

Depends if there is a lot of curry eaten, if so there will be no solids problem

On condensate drain I think these have to be an open connection ... i.e a drop to a drain on over a tundish ... to prevent back siphon ? That is way I have always put them in .... with a fall, any fall :-)