Soil pipe alignment tolerance?

[Malc]

Hi,

Is there a specified alignment tolerance for soil pipe. I've looked at various manufacturers sites but can't find anything. My problem is that I need a true 90deg bend for a horizontal run. Using a 87.5 deg bend gives me 1:23 so 2m run would be 87mm drift. I presume there must be a misalignment allowance in a fitting so I could lose some of the 2.5 deg in that but I can't find a figure for it.

Thanks.

 

[polesapart]

Never a good idea to run a soil branch dead horizontal.

 

[reds42]

I've found there is a bit of wiggle room on push fit fittings, but not realy on solvent fit.

As already mentioned you dont want a truley horizontal run, you need to meet minimum required fall to stop blockages.

 

[just pumps]

Hi,

Is there a specified alignment tolerance for soil pipe. I've looked at various manufacturers sites but can't find anything. My problem is that I need a true 90deg bend for a horizontal run. Using a 87.5 deg bend gives me 1:23 so 2m run would be 87mm drift. I presume there must be a misalignment allowance in a fitting so I could lose some of the 2.5 deg in that but I can't find a figure for it.

Thanks.

Show your calculation to explain?

 

[Malc]

Yes I meant horizontal with a fall. I'm aiming for 1:40 or 1.5deg.

Well I've got outside vertical stack, with a socket at 87.5 deg in the vertical. So from drain pipe comes up vertical, following wall. Then it turns 90deg and runs parallel to wall in plan view with a 2.5deg up slope (i.e. fall as this is going from drain). So far so good. The socket in the stack can rotate so horizontal pipe is parallel to wall. Now I want to turn 90deg and go through wall but the bend is 87.5 deg so I'm not going through wall at 90 deg. Inside I have about 1m run then I want to turn 90deg and have a 2m run to the WC (viewed looking down, will a fall of course).

2.5deg is 1:23 (1:40 is ~1.5deg). So 2m run is 87mm off square, i.e. 87mm away from wall at one end and touching at the other.

 

[reds42]

I'd think you would get away with that angle with pushfit stuff, particularily if the bend was pushfit at each end.

 

[just pumps]

Total length of run?

 

[Newboy]

3 elbows in the wet section is a bad idea

 

[Malc]

Length is about 4m to WC. Sink/bath/shower feed into soil too so only the first 1.5m is just WC hence the elbow shouldn't be a problem as lots of plain water flowing to wash stuff down, not just WC flushes.

 

[just pumps]

Length is about 4m to WC. Sink/bath/shower feed into soil too so only the first 1.5m is just WC hence the elbow shouldn't be a problem as lots of plain water flowing to wash stuff down, not just WC flushes.

Can`t remember the max run allowed, 4m/8m? sure somebody will know.
Plenty of water maybe but little oomph.

 

[Newboy]

6m max

 

[reds42]

So long as the overal length is no longer than previously stated it would probably work ok. Building control don't like many bends though.

I have a run about 4m with a couple of swept 90 bends (not quite 90 ) and a 45 to get a pipe running between joists, then dropping below them and running accross them to outside stack with no issue.

Edit: probably be good to put access point bend through wall so you can rod any blockages.

 

[Malc]

Building regs say nothing about bends, just length and fall. According to this the discharge rate for a full pipe, 10cm inside diameter, 25mm/m, is 13l/s. Full flush is 6l and takes about 3s I reckon. Peak flow say 3l/s so pipe is only quarter full at most. The important thing I reckon is to keep the fall not too much on a long run so as not to leave the solids behind. Bath/shower/sink water joins before the 1st horizontal bend so H bends are all well washed (there is a vertical bend at WC).

I did think about access bends but instead I went for splitting horizontal external pipe near bend and using a double coupler as a sliding coupler. That gave me more options and allows disassembly of stack, if it is even needed. Other option is to use a drain clearing tool (springy wire thing you turn, don't know what the proper name is). Those go round bends (and do 32mm and 40mm pipe). I could use that from outside or take the WC bowl out and go from inside.

 

[Malc]

I've tried some fittings and agree with reds42. Solvent weld have very little play but ring-seal have more. My MkI eyeball reckons that 1 ring seal joint can maybe allow a 87.5 deg bend to stretch to 90deg, certainly I reckon 2 seal (each end of the bend) would allow this.

 

[reds42]

There are 90 degree knuckle bends, but probably not the best to use mid run when you need to keep things flowing smoothly.