Soil Pipe Design

[flappy8]

https://dl.dropboxusercontent.com/u/4720725/bathroom soil.jpg

Hi All,

Following lots of conversations between the builder's plumber and building control a design for a bathroom in the centre of the house has been agreed. I've attached a sketch above.

Given that the pipe from the pan running past the basin, shower and bath connections only has a slight falls will the velocity be slow enough not to pull any of the those traps?

Unfortunately its only possible to have this branch on a Durgo.

The 'horizontal' runs are just under 2.5 m each

Any thoughts/comments/criticism appreciated!

 

[oz-plumber]

I would be more concerned about the fall of the waste pipe from pan than anything else.

If you can't get the recommended minimum fall for that section of pipe, then I wouldn't be too concerned about much else.

Reasoning: One day you might be standing in the shower - the drain is blocked due to not enough fall from the pan - and all of a sudden you are standing in **it.

Yours and everyone else who has used the bog recently.

 

[Best]

You have shown an AAV on end of soil pipe before the pan. This should help stop any suction of other things beyond that - shower & basin traps etc.

 

[Reg Man]

Minimum fall for soil stack 18mm per metre length. Part H Building Regulations.

 

[flappy8]

Oz - I can achieve the min shown in the regs as Reg-man details. Indeed I could probably achieve a greater gradient although I did read that if you go too far the liquid goes to fast and leaves the solid.....

Generally do people go for greater than 18mm/m if they can?

 

[Reg Man]

Not greater than 90mm per metre though.

 

[Best]

Oz - I can achieve the min shown in the regs as Reg-man details. Indeed I could probably achieve a greater gradient although I did read that if you go too far the liquid goes to fast and leaves the solid.....

Generally do people go for greater than 18mm/m if they can?

Too much fall will not help with flushing away solids.
No need to fall more than the 18mm/m.
110mm "90 degree" bends are not actually that - they are 87.5 degrees to allow for proper fall, as is the centre of the junctions (tees).
Truth is if the soil pipe is just falling in a short distance of 1 or 2 metres, but properly clipped or supported, it will be fine.

 

[Ermintrude]

Run bogs and sanitary goods separately! Aav has a minimum opening pressure also I hate gurgling !

 

[flappy8]

Run bogs and sanitary goods separately! Aav has a minimum opening pressure also I hate gurgling !

I was hoping that the slow fall and AAV would prevent gurgling. Unfortunately making this open-vent just isn't possible.

 

[Ermintrude]

Aav is fine just don't tie bog into shower and sink run.

 

[Ermintrude]

And run bath separately

 

[flappy8]

Aav is fine just don't tie bog into shower and sink run.

Do you mean not connect them to the stack until it's vertical?

 

[Ermintrude]

Yep. U could even route a 50mm solvent across ceiling dropping down to each appliance , so instead of an elbow out of wall u have a tee. With the top part being a free vent back to stack.

 

[chris watkins]

It will be absolutely fine as drawn flappy8 the AAV will never operate.
Run bath & shower in 50mm & basin in at least 40mm reducing at the traps.

Although AD part H state 18mm/m minimum the reality is with a well installed plastic soil pipe with a vertical drop from the pan to start with you could get away with less.

Head of run should always be vented if at all possible, did you consider a loop anti at high level back to the vent ??

 

[flappy8]

........

Head of run should always be vented if at all possible, did you consider a loop anti at high level back to the vent ??

You mean throwing the AAV and extending to the open vent pipe? Not practical because the roof is hipped all the way round

 

[flappy8]

Yep. U could even route a 50mm solvent across ceiling dropping down to each appliance , so instead of an elbow out of wall u have a tee. With the top part being a free vent back to stack.

I see where you're going - unfortunately practically that would be a nightmare!

 

[Ermintrude]

But it would work like a dreAm!