New Build Queries

[umiq88]

Hi going in to a new build and looking for some advice on drainage pipe in the ground works. 

 

Has anyone any useful technical publications or guides to design and fitting?

 

My current house uses S bends on all the sinks directly into an outside gulley (with air break) but the modern approach seems to be everything goes into 4" soil pipes and into the septic system. In this case I presume every trap needs to be P trap and vented?

 

I'll have block internal and external walls so in a bathroom with a sink up against a standard 4" wall how do people run the vent pipes? I could do block on flat and chase a 32mm pipe into the wall?

[ProDave]

To be clear are you building, or moving into a ready build new build?

 

S and P traps do the same thing, that's a matter of style, if on show a P trap often looks better or even a bottle trap.

[umiq88]

Sorry I'm starting a self build.

 

The way I've seen new builds done is a P-trap feeding into a T. Bottom goes to waste and the top is vented. This means you can't pull a vacuum and empty the trap. 

 

S trap is unvented. 

 

I'm just wondering how big a deal it is and if required how people run vents up in block walls.

 

 

[ProDave]

Normally if done properly there is no need to vent the small pipe from the sink / basin, it goes into the 110mm stack pipe which is vented or sometimes just vented with an AAV.

 

You only fit a local small AAV if you find the trap is getting sucked dry.

[Crunchynut]

I agree with @ProDave, however you can now get a P Trap with integral inlet vent for a tenner, and if that means you never hear a gurgle as your water goes don’t the plug hole then it’s worth doing in my book.

[S2D2]

On 13/09/2023 at 09:32, Crunchynut said:

I agree with @ProDave, however you can now get a P Trap with integral inlet vent for a tenner, and if that means you never hear a gurgle as your water goes don’t the plug hole then it’s worth doing in my book.

Thanks for the tip, couldn't find one of these at the time of install but swapped out the P trap of a SK1A with this and it's much quieter now.