Best sewer pipe system and slope

[MikeSharp01]

Am just about to commence digging the sewer trench for our new builds first phase and am getting bewildered  by the range of pipe systems I can use for the foul water and the drop I should adopt in readiness for the BCO. I am going for 1:60 drop that allows me to stay 600mm below the surface for the whole run which terminates in a connection to the existing foul drain running down behind the houses in the street. (1:40 brings me too close to the surface at the far end of the run and would put the pipe in the slab insulation.) This existing drain is 150mm (outer) cement / concrete pipe by the looks of it. This first run is a drop from the toilet and sink round a 90 deg bend and then a 19m run to the existing pipe. Should I use solvent or push fit and which of the massive range of systems has the best reputation as this pipe will run under the slab for 4.8m I don't want to dig it up! (I can put an access point at the edge of the slab if 19m is too long without access.)

 

Any thoughts.

 

[Crofter]

Solvent weld is the way to go, dead easy to use and pretty bombproof.

[MikeSharp01]

Sounds very sensible any thoughts on which system, or any that comply with BS4962?

[Declan52]

Check the depth of the pipe wall. Some are thicker than others. I always liked Brett Martin.

[Ferdinand]

I think the BRs relate fall to pipe size which you do not specify.

 

I have a bungalow with a slack drain and it is a PITA if anyone puts flushable medical wipes down it.

 

If it is just your family you may be OK with pushing the limits but I would avoid walking the line if I could. It is just unpleasant when it goes wrong.

 

Ferdinand

Edited October 27, 2016 by Ferdinand

[PeterW]

Don't go with the cheapest for underground UPVC - Brett Martin is good, as is Polypipe. I would always use longest possible pipes, preferably 6m single socket lengths that on the face of it seem a little more expensive but you will find that they are much easier to handle and get the falls correct.

[Oz07]

1:60 is fine with good workmanship on 110mm. I've just gone 1:80 on a job to keep it low as you say. I've never used solvent weld underground so couldn't comment. If you did ever have a leak though don't forget they repair them from inside the pipe this day and age!

[MikeSharp01]

1 hour ago, Ferdinand said:

I think the BRs relate fall to pipe size which you do not specify.

It will be 110mm as this will best match the concrete scheme it has to to connect to.

 

 

[Vijay]

When would you use 150mm?

[CC45]

I asked BC about falls when we did sewers - for 1:60 he advised 150mm pipe (less sag apparently). We stuck to 1:40.

 

CC

[ProDave]

If you lay a sewer pipe properly, there will be no sag. You are supposed to lay it on a bed of pea gravel and then infill around and over it with pea gravel,

 

Yes if you do what most builders do, support it on bricks in the trench, then just shovel the earth back on top, it is going to sag, but no self respecting self builder would do that would they?
 

[daiking]

1 hour ago, ProDave said:

If you lay a sewer pipe properly, there will be no sag. You are supposed to lay it on a bed of pea gravel and then infill around and over it with pea gravel,

 

Yes if you do what most builders do, support it on bricks in the trench, then just shovel the earth back on top, it is going to sag, but no self respecting self builder would do that would they?
 

 

If you discovered the pipe had been propped on bricks and backfilled with rubble strewn earth,

 

Would you dig it out and re-do it?

[Barney12]

1 hour ago, daiking said:

 

If you discovered the pipe had been propped on bricks and backfilled with rubble strewn earth,

 

Would you dig it out and re-do it?

 

If it had been there a long time without any issues AND the ground wasn't going to be disturbed by other works...........probably not.

[daiking]

1 hour ago, Barney12 said:

 

If it had been there a long time without any issues AND the ground wasn't going to be disturbed by other works...........probably not.

 

It hasn't been there long (12months) and could be disturbed with future garden groundworks...

[Declan52]

The problem happens more on new sites as the ground is disturbed that much so will take time to settle and sink. If the builder has used bricks under the pipe, complete madness in book, then when the ground sinks you end up with the brick indentations the pipe. This is where all the good stuff that gets flushed will settle and you end up with a blocked pipe. 

If I was going to dig up the area again I would take the bricks out and just keep an eye on it in the meantime.

[MikeSharp01]

On 27/10/2016 at 11:58, Ferdinand said:

I think the BRs relate fall to pipe size which you do not specify.

Sorry - got the wrong end of the stick - they do relate fall to pipe size I can have 110mm (100mm internal) because my flow rate is >1 l/s with just one WC. If I had more I might need 150mm but not until I have 5 WCs (the house itself has just 3) so 110mm shoudl be fine. Its table 6 in part H that shows the rules so I can have down to 1:80 as the shallowest slope, table 6 says minimum, it would be 1:40 if the flow rate was <1 l/s. Naturally it will be in pea shingle all round so sag won't be a problem.