Basin waste drop

[davidjhope]

I've done a quick search and nothing seems to answer my question.
I'm installing a new basin and the waste will be joining behind the toilet into an existing boss. The length of the run is 700mm to a 90 degree bend then a short 200mm run.
What drop should I do? And would this affect the 90 degree bend going up to the bottle trap.
Thank you

 

[Hugh Jaleak]

Only need a couple of degrees, as long is its pointing slight downhill in the right direction, it'll be fine.

 

[davidjhope]

That's the answer I wanted to hear. Thank you for your prompt reply and reassurance.
David

 

[Doggit]

1 in 40 drop means about an inch per metre; simple rule.

 

[davidjhope]

Thanks doggit.
With a 1 in 40 drop that would affect the angle at the end to go up to the bottle trap. How do you overcome this discrepancy?
Sorry if this is a stupid question.
David

 

[Doggit]

It's just a slight twist on the pipe, so there should be enough give on the joint out of the bottle trap to handle it.

 

[Nige F]

Go with Hugh, and don't use a 90 degree- Use a 92.5 swept bend. Then it'll look like a plumber did it. and soap+hair won't snag up on the inside of the 90. ( poxy useless things)

 

[picasso]

1 in 40 drop means about an inch per metre; simple rule.

Good to see metric and imperial being used together.

 

[Nige F]

That's 6.0 of 1 and half a dozen of the other

 

[Doggit]

I think it's one of life little niceties; a metre is 39 1/2 inches, so makes a very nice 1" drop over a metre. 25mm doesn't work so well for me.

Actually, 1 in 40 is 1.4 degrees, so a couple of degrees drop would be more than required.

 

[Madrab]

1 in 40 drop means about an inch per metre; simple rule.

An inch per metre? metric and imperial D, sitting on the fence? You heathen

OP ... REGS ask for between 18 and 90mm per/m run to allow for self cleaning, minimising trap pull and minimising noise, anything from 25 > 45mm per/m is optimum IMO.

 

[Doggit]

I like to think "flexible" is a better description of my way of thinking, but you could be right. But as to 18-90mm per m run, 90mm would guarantee trap pull without a shadow of a doubt. 25mm is 1:40, but 45mm would give 1:22 which is way below anything I've ever seen recommended. I've seen 1:80 for gutters, and sometimes for horizontal soil pipe runs, (which I'm also suspicious of)

 

[John D v2.0]

You can get away with flatter and steeper falls if you have plenty of toilets attached to flush everything through. For sinks and showers you have to be more strict though.