Subfloor pipework

[BurstPipe]

Good afternoon all,

I have commenced an extension to my house and as part of this includes the main bathroom.
The proposed floor construction make up is 150mm type 1, DPM, 150mm concrete, 150mm Insulation, and 70mm Screed.

I plan to have all the subfloor pipework popups in-situ prior to pouring the concrete slab.

However, I have a few questions which I would be grateful for some advice:

1. What level should I run the sub floor pipework at? Within the type1 layer for the WC, sink, shower & bath? Surrounding the pipework in pea gravel.

2. Should I install 110mm underground pop ups to all fixtures & common them below ground to a main 110mm line? I had then just planned to install adaptors within the installation layer for the sink, bath & shower popups proposed to use 50mm for each.

The common 110mm would just go through foundations blockwork walls before discharging into a new external inspection chamber.

I plan to install a vent pipe upstream of this manhole to ensure the drain is ventilated.

Thanks in advance,

 

[BurstPipe]

Here is the plan layout as approved by BC although my wife is considering shuffling the fixtures about a tad:

 

[Chalked]

Main thing get right is your toilet drain. That needs to go in before any build up. The wastes, hot and cold, can be run in the insulation layer.

 

[BurstPipe]

Main thing get right is your toilet drain. That needs to go in before any build up. The wastes, hot and cold, can be run in the insulation layer.

Thanks chalked.

Is there a standard dimension to the centreline of the WC popup off the finished wall?

 

[BurstPipe]

I've seen online that this is typically 12" in the US just wasn't sure if UK had typical standard? Or is this toilet specific?

 

[Chalked]

Are you in the uk?
If so, 5 inch to centre of block wall will cover most uk toilets.

 

[BurstPipe]

Yeah in Scotland!
Thanks for that info! [emoji106]

 

[BurstPipe]

Plan above is poor quality so have reposted....

 

[BurstPipe]

This is what I sketched up yesterday when trying to plan the subfloor pipework based on wife's preferred fixture layout...any advice / comments appreciated..

 

[lame plumber]

you seem to be adding vents all over, you may wish to take advice from a professional on site and adopt the standards we tend to use now, ie 4 inch soil stack vented at one end with the wastes following into the main stack. if you use an architect their plans should have the basics right but use a good plumber who has done his training and time to ensure the regs are being followed for the best results, to avoid simple errors that you will have to live with thereafter. After all, you have no recourse against a forum, but you do against your contractor if he plans the system for you.

 

[BurstPipe]

Hi lame, the problem I have is the sub floor pipework as I have drawn will not achieve greater than 450mm from invert of soil stack to invert of sub floor pipework as per Building regs. This is the reason I considered combining all connections and discharging these into an IC. I then planned to install a vent stack at the head of the run to ventilate the main drain.
I was unsure if this would achieve adequate venting therefore I questioned the need for additional venting at the head of the combined connections.

 

[lame plumber]

Hi lame, the problem I have is the sub floor pipework as I have drawn will not achieve greater than 450mm from invert of soil stack to invert of sub floor pipework as per Building regs. This is the reason I considered combining all connections and discharging these into an IC. I then planned to install a vent stack at the head of the run to ventilate the main drain.
I was unsure if this would achieve adequate venting therefore I questioned the need for additional venting at the head of the combined connections.

best get someone on site with your architects drawings to get an answer.

 

[BurstPipe]

best get someone on site with your architects drawings to get an answer.

The extract shown above is from the approved architect drawings. These however are rather vague, hence the reason I was seeking further guidance on here.

 

[AWheating]

run 110mm to all positions using 110mm to waste size at screed level, maybe fit a vent pipe in corner by toilet to be boxed in with a aav or through roof for open vent. your building control officer should be able to advise you further.

 

[BurstPipe]

Thanks AWheating! My original sketch was rather 'sketchy'....so
I will resketch and repost to see if I have interpreted you correctly.

 

[BurstPipe]

Downloaded sketchup & knocked the below up to try and explain better.

Proposing W/C directly into inspection chamber in 110mm. The sink, shower & bath increasing to 110mm at screed finished level and the communing the three up in 110mm under concrete slab and connecting into the Soil Vent Pipe before discharging into main drain heading towards inspection chamber.

Reading the regulations I am still unsure if I require additional venting of the combined branch or will lengths of pipework & the oversize pipe eliminate the need??

The bathroom is only 2.3mx3.1m.

Thanks in advance,

Cal

 

[oz-plumber]

Is your budget that tight that you can't afford 4 hours for a Plumber to come and do the drains?

As for venting - need to know whether the main drain outside is vented.
There is a distance you can run an unvented branch drain. It depends on length of drain, size of drain and amount of fixtures the drain is picking up.

I would hazard a guess that the whole bathroom doesn't need a vent at all, and all the drains could be combined.

But what would I know - only been Plumbing for 25 years.

 

[BurstPipe]

Is your budget that tight that you can't afford 4 hours for a Plumber to come and do the drains?

As for venting - need to know whether the main drain outside is vented.
There is a distance you can run an unvented branch drain. It depends on length of drain, size of drain and amount of fixtures the drain is picking up.

I would hazard a guess that the whole bathroom doesn't need a vent at all, and all the drains could be combined.

But what would I know - only been Plumbing for 25 years.

Hi Oz,

I had a plumber/GSR engineer round this week servicing my boiler & @ the same time did asked if he did underground slab pipework works. Unfortunate he said it was was typically left for the ground workers to do.

You local?!? I'm south of Glasgow. Happy to employ the services of a plumber to assist in giving me some guidance.

Cheers.

 

[brum]

That can be totally simplified if it was a new build there would be one four inch pipe leaving building only with everything else branched off it but don't forget access boss ...brum

 

[brum]

Having a better look at drawing 4inch pipe from basins etc needs,to terminate in IC to allow testing for building control..brum

 

[BurstPipe]

Cheers Brum. Have dropped you an email.