Critique my sewer plans

[Artrax]

Hi All,

I'm installing some new soil pipes as part of a new extension. I've attached my plans and I'm just wondering if I should change anything before I start installing it all and then arrange for my BCO to come and inspect. Fall will be 1:70 but this isn't really shown in the pictures.

The stack shown in the drawing will service: ground floor utility room, shower room with w/c; first floor bathroom with w/c. Gully 2 will service a kitchen only and the stack on the opposite side of the house (not shown) will be a first floor ensuite with w/c. Both gulley's are roddable, but not sure if I will require additional access points?

The first floor isn't in yet (loft conversion on a bungalow) so I haven't concerned myself with the detail of those connections to the stack just yet.

Thanks!

 

[John D v2.0]

Fall seems a bit tight given how low the invert in the inspection chamber is, can't you push it up to 1..40 to get more leeway?

 

[Artrax]

Thanks John D. Well if the fall is the only criticism, then I'll take it. I can work with that!

1:40 would be a steeper gradient, right? Sure I could do that. Surely a steeper gradient would mean tighter bends though, right? Or is the intention to give the waste more momentum?

 

[John D v2.0]

Oh I didn't go through the whole lot!
1.40 would be slightly more obtuse bends, but not that you'd notice. The standard bends are about 92.5 degrees although they are flexible enough for either.
Let time I checked, at least 1.40 was the recommendation in British standard whatever, but you can go lower if necessary if you do it accurately. It's very easy for 1.80 to end up going uphill in places.i just couldn't see a good reason in your case hence the comment.

 

[Artrax]

Thanks. I'll go for 1 in 40 then, plenty of depth to allow for it.

My main concern was that some of the connections might not be allowed without some additional access points.

Is gully 1 required? I'd like to do away with it, but figured it would be required for access?

 

[John D v2.0]

The whole thing seems a bit complicated, but basically you want to feel confident to clear all runs from either inside or outside, ideally going downstream.
Looking at the diagram you seem to have separate runs that could be combined (left hand room on the first drawing)
Other than that I can't really advise, I'm just a DIYer. I'm surprised no one else has posted, you could try the plumbing section?

 

[^woody^]

I was under the impression that back-drops were frowned upon nowadays. Can one even be formed in plastic riser rings?

Some of those bends look a bit tenuous, and difficult to access for rodding.

Agree its a bit complicated, too many individual pipe runs?

 

[Artrax]

I would have thought that more individual runs would be better than combined ones? Less impact if a blockage occurs?

If necessary I could combine the second gully with the pipe coming from the second stack, that would reduce the number of individual runs to the IC.

I could also add an access point at the first bend upstream of the first gully, that would give additional access for rodding.

Not sure about the backdrop, I got the idea from pavingexpert. I can ask my BCO when they come to inspect the first section as the backdrop won't be install until a bit later. I was just trying to avoid digging a 10m trench to the same depth as the IC.

Cheers

 

[jeds]

Is that a surface gully connected to the foul? Technically, you should rule out the possibility of a soakaway first, but I wouldn't worry unless the BCO mentions it.

 

[Artrax]

Thanks jeds. There are separate plans for a soakaway for the gutters/down pipes. I only added the gully's in to take the grey waste from the kitchen/utility/bath etc, but decided to bring these underground instead of through the wall and into the top of the gully.

 

[^woody^]

Generally, you would risk asses the likelihood of a run becoming blocked by virtue of its usage - frequency and what is going down it.

So infrequent solids or mainly liquid effluent would be deemed less likely to block so bends and access could be less stringent. Similarly, more connections to a single run would tend to keep it flowing.

Fewer runs, with fewer bends and connections is generally at less risk of having problems.