Soil/waste pipe routing options

[wookey]

Not particularly green building, but as a side-effect of new (reasonably green) extension I need to move soil pipe and re-plumb bathroom wastes. I've drawn up a couple of possibilities. 'Option1' with one hole through the wall, and the bath+sink plumbed ino the WC waste, and 'Option2' with two holes: one for WC, one for bath+sink. In the former case I'm not sure how bad an idea a branch right by the back of the loo is - will it be prone to bunging up? Will flushing the loo syphon out my basin/bath traps? Is an 87 degree branch better than a 45 degree one? (I assume not, and I'm not sure it will fit). If I go for keeping the branch waste separate all the way to the soil stack what do I do about the fact that it arrives too high for a strap-on boss into the stack? Wiggle round the side, just make it steeper than recommended, put in a couple of bends to drop lower? (It's all much easier when the stack is on the wall _behind_ the loo/basin/bath).

Another consideration is that external wall insulation is planned for the front of the house, which will hopefully go over the outside of the soil pipe. Does an enclosed pipe have to be done in solvent-weld, rather than push-fit? I saw that claimed on-line but can't find any evidence in Approved doc H or BS 12065 (gravity drainage).

Suggestions on how best to do this very welcome, as I'll probably have no plumbing later this week.

Option1:
http://wookware.org/extension/builders/pdf-drawings/soilwaste_opt1.pdf

Option2:
http://wookware.org/extension/builders/pdf-drawings/soilwaste_opt2.pdf

[Heinz]

I'd think option 1 will suck the water out of the bath/sink traps.
Why not drop the soil pipe height in option 2 to the height of option 1 and get the bath/sink connections at the correct height? Why not drop it a smidgen further and 'lose' the waste pipe within the joist height?
I used push fit for all my internal 40mm waste pipes, some of it exposed and some in the walls/floor. Brilliant stuff with absolutely no leakage problems, unlike the carp brittle solvent weld stuff which I removed...  Mr Planning Man was quite happy with it.

Heinz

[Brandon]

wookey, a dergo (sp?) air admittance valve will stop the toilet sucking on the traps, just put in on a tee as the first fitting on the 40mm.

[titan]

You could fit Hep V0 valves in place of the traps.  http://hepworth.wavin.com/master/master.jsp?products=products&middleTemplateName=oc_middle_system_detail_I&FOLDER%3C%3Efolder_id=2534374305482315

[tony.]

Mineis fitted likeoption 1


I had a soil connector for the toilet that has a built in 40 mm connection so that helps reduce joins. Etc and it also ensures a further clean of the pipes after the toilet is flushed, that the tap water further cleans the soil pipe.


I have had no problems in over 5 years

[tz0c0s]

Hi Wookey,

http://www.screwfix.com/prods/42968/Plumbing/Solvent-Weld-Waste/FloPlast-Air-Admittance-Valve-32-x-40-x-50mm
is a small cheap air admittance (durgo) valve.

I would run each waste pipe separately.

Would this be of any help ?
http://www.screwfix.com/prods/22367/Plumbing/Soil-Vent/Waste-Manifold-Grey-SP588

Don't forget the maximum recommended length of run in 32mm pipe is 1.7M & 40mm is 3M

Also as you are discharging into a stack, you need a trap on the bath with a 75mm seal. Not a shallow bath trap.

Regards Andy

[ericw]

When I did my soil pipe several years ago now, similar to #2 there was a minimum spacing requirement from the toilet branch to a lower waste branch which forced me to use 2 bends to step down.

[wookey]

Heinz - dropping the soil pipe would make option 2 back into option1 as the waste pipe is inline with the soil pipe, unless I add horizontal bends to make it run alongside. In general fewer bends is better, right? But yes I suppose it could work, with a sharp bend into the boss on the side of the branch conector on the stack. The boxing in the bathroom would have to get wider, or steal some insulation space. It was thinking about this that made me think that inlining all three things made for a rather neater install (and one fewer thermal bridge) in the first place.

Tony - where did you find a toilet soil connector with a 40mm boss in it? I failed to find such a thing. Although actually, assuming the boss is at the toilet spigot level, that won't help because the bath/basin waste pipe can't join that high (unless I put the bath on a 200mm pedestal.

tz0c0s. I'm within the 1.7 and 3m pipe limits(this is an english bathroom :-), and those are only for unventilated branch lines. Adding a durgo valve makes it ventilated (I think?) so then they could be longer. Good point on the bath trap depth, It looks like a shallow trap currently. Mind you it's also discharging into a stack now and it's working fine, so that's clearly an 'it depends' in practice.

And the advantage of the HepV0 valves is that, being dry, there can't be a problem with siphonage. I have seen it suggested that they are a bit more prone to blockage? Do we think that's true (Normal traps get blocked from time to time anyway)? OK, so we have multiple solutions to the potential siphonage issue: durgo valve and/or HepV0 valves. Pros/cons? One durgo does both bath and basin.

I think I'm still favouring option1. Any opinions on relative merits of 45 degree branch vs 87.5 degree branch? Strangely you only seem to be able to get these in brown (intended for underground use) if you don't want bosses on the side. I can mix brown 'underground' 110mm pipe with grey above-ground if I want, right? So far as I can tell they are the same moulds these days, but you never know. I remember finding that there were two different sizes of '40mm' waste pipe some years back...

Now I just have to worry about making it all actually fit. There isn't much space to spare behind bog.

[JohnS]

The brown stuff is not UV protected, but I guess that is not a problem in the bathroom.

John

[tony.]

Mcalpine plumbing products.
Wc bp1

Cant figure out this ipad for cut copy paste.

Tony

[Eco Andrew]

Tony said, "Cant figure out this ipad for cut copy paste."
My wife says, "Hold your finger on the bit you want to copy."

Hope that helps

[Heinz]

Heinz - dropping the soil pipe would make option 2 back into option1 as the waste pipe is inline with the soil pipe, unless I add horizontal bends to make it run alongside. In general fewer bends is better, right? But yes I suppose it could work, with a sharp bend into the boss on the side of the branch conector on the stack. The boxing in the bathroom would have to get wider, or steal some insulation space. It was thinking about this that made me think that inlining all three things made for a rather neater install (and one fewer thermal bridge) in the first place.

No, The problem with option 1 is that the bath/sink pipe is not vented. By dropping the soil pipe down and connecting the 40mm at the outside T, (there's normally a boss on the side of the soil T for this purpose) both the WC pipe and the 40mm bath/sink pipes are vented.
I suppose you don't need to drop the soil pipe down, but it would mean you can use the boss on the T rather than needing an extra fitting to connect the 40mm to the soil pipe.

Heinz

[KLD]

Tony - where did you find a toilet soil connector with a 40mm boss in it? I failed to find such a thing. Although actually, assuming the boss is at the toilet spigot level, that won't help because the bath/basin waste pipe can't join that high (unless I put the bath on a 200mm pedestal.

Well, once you put a bath in like this here,
http://www.fotosearch.com/DGT089/42-17196456/
then a pan connector like that there might do:
http://www.drainageonline.co.uk/Pan-Connectors/Straight-Pan-Connector.htm ?

K