Help with drainage locations - slab being poured next week

[MG-Wales]

It looks like next week the groundworkers will be laying the below ground drainage pipes before pouring the ground bearing slab.

 

This is to be done based on the plans I've drafted (see some screenshots attached of substructure plan/GF plan/FF plan, vertical drains are highlighted in yellow), however I have not a great deal of experience with plumbing and drainage (I mostly deal with them in apartment type buildings, etc.) so there was some degree of educated guessing involved.

For the past weeks I've tried to discuss the drainage arrangement with a couple of plumbers but I've only got as far as sending them the drawings and struggled to get hold of them afterwards.

Hopefully one of them will have looked at the plans by Monday and can assist, but I thought just in case I'll ask the forum and any plumbers in here if what I've shown on the plans makes sense.

 

My main questions:

 

- Sink in the utility: can it connect to the nearby toilet soil pipe, together with shower and bathroom sink, or does it need its own waste water drain going all the way to the outside ?

 

- Are 2 SVPs to serve the 3 bathrooms upstairs about the right amount? Or should it be 3? Or 1 would be enough? There is potential for a future 3rd toilet in the attic, so I thought 2 should be about the right amount?

 

- Do MVHR or Cylinder/Buffer tank require a connection to the drains? If so, can it be one of the SVP nearby?

 

Note: my first floor is to be 253mm deep Metal Web Joists, and I've got the option of dropping the ceiling level over the kitchen/diner to let the plumbing across to the service shaft. So I'm not too concerned about the upstairs bathroom connecting to the drains I've shown.

 

Any suggestions are much appreciated!

[nod]

On our previous build and our current build My wife couldn’t decide on the location of either Or most of the kitchen Telling me that we have ages and can always move drains 

I put one either side of the kitchen and utility Your only talking a small amount of work and Pennie’s 

[Temp]

16 hours ago, MG-Wales said:

Sink in the utility: can it connect to the nearby toilet soil pipe, together with shower and bathroom sink, or does it need its own waste water drain going all the way to the outside ?

 

I would put an inspection chamber at the top of the drawing between house and road. Connect 110mm pipe from that to rest bends at the bottom of each stack. Also run 110mm pipe up through the floor under the utility sink. Below the sink use adaptors down to suit the sink waste pipe.

 

16 hours ago, MG-Wales said:

Are 2 SVPs to serve the 3 bathrooms upstairs about the right amount? Or should it be 3? Or 1 would be enough? There is potential for a future 3rd toilet in the attic, so I thought 2 should be about the right amount?

 

How thick are your floors? You appear to have/need to run 110mm pipe from the main bathroom backwards in the floor under the corridor to one of these the 2 stacks. Might be better to have a stack in the bathroom? But you have dining room below?

 

You also have 110mm from one of the ensuites going under the door of the other to get to a stack. Drilling 110mm holes in joists might be possible but can be difficult to get enough fall as well.

 

16 hours ago, MG-Wales said:

Do MVHR or Cylinder/Buffer tank require a connection to the drains? If so, can it be one of the SVP nearby?

 

Yes and I think that's OK.  MVHR has a condensation outlet which is small bore. Pressurised heating system have a pressure relief valve and I think that can go to a svp via a tun dish.

 

[MG-Wales]

19 hours ago, Temp said:

I would put an inspection chamber at the top of the drawing between house and road. Connect 110mm pipe from that to rest bends at the bottom of each stack. Also run 110mm pipe up through the floor under the utility sink. Below the sink use adaptors down to suit the sink waste pipe.

 

Thanks for your reply, that's what we're planning to do. I think it may be wise to add the additional drain under the utility sink as you suggest, this can also be an alternative drain for the toilet shower if it is unpractical to connect to the toilet svp. The cost of adding a drain run to the inspection chamber at this stage should be around £200 and it's not worth risking having issues with connections later on.

 

19 hours ago, Temp said:

How thick are your floors? You appear to have/need to run 110mm pipe from the main bathroom backwards in the floor under the corridor to one of these the 2 stacks. Might be better to have a stack in the bathroom? But you have dining room below?

 

You also have 110mm from one of the ensuites going under the door of the other to get to a stack. Drilling 110mm holes in joists might be possible but can be difficult to get enough fall as well.

 

The floor is going to be 253mm deep metal web joists (159mm space in between the flanges). Taking in consideration the span and spacing of the joists, I've modelled the drains and it should be ok to connect WC and bath in the family bathroom to the nearest SVP across the corridor. If this is not possible for unforeseen reasons, there is the option of dropping the ceiling over the kitchen and part of the dining, but I hope this will not be needed.

 

The WC (and everything else) in the ensuite on the left hand side could also connect to a continuation of the SVP from the downstairs tolilet. This would be located roughly where the wall between the 2 ensuites is, which is non loadbearing. I think this may be a more practical solution than running the pipe all the way to the SVP in the vertical shaft.

 

[Dave Jones]

move your toilets to stud walls to avoid the unsightly boxing in, lose the pipework in the stud.

[Temp]

7 hours ago, Dave Jones said:

move your toilets to stud walls to avoid the unsightly boxing in, lose the pipework in the stud.

 

or failing that false walls look better than boxing if you dont mind losing the space.

 

Personally we quite like wall mounted taps and spouts as they stay cleaner longer and false walls make that lot easier.