Bathroom waste layout

[flemish4]

Hi!

I'm currently planning a new bathroom and have a few questions, hopefully someone can help 🙂
All of the coloured lines on the diagram are waste pipes.

1. The red waste from the shower will be around 5 metres to the stack which is too much to meet regulations (3m for 40mm and 4m for 50mm) although this is actually already present. I am planning to put in a false wall next to the shower and a half wall next to the bath to hide the plumbing so there is space to put in an air admittance valve next to the bath which will be accessible. Is this a reasonable solution?
2. The bath waste in green is new, from what I have read it is advisable to run a separate waste all the way to the stack? Or is it possible to tee in to the red shower waste? Would connecting up to the air admittance valve help?
3. The blue vanity waste will have a AAV trap and will then drop into the wc waste pipe. Does that sound okay?
4. The soil stack diagram to the right is what would be needed if a separate bath waste is advisable. They would all need to be quite close together but I think because they aren't opposing this is acceptable?

Thanks for any advice!

 

[flemish4]

I have just thought, is it possible to join green and red at 2 and make it a 100mm pipe, I think that would satisfy the length regulations and will simplify the connections to the soil stack to just two.
Does that also remove the need for a AAV?

 

[ShaunCorbs]

Yep best to install an aav when more than one appliance is tees into the same waste

yes that’s fine if you can connect it on the top of the 110mm waste

50mm pipe will be more than enough From point 2

 

[flemish4]

Thanks.
Small follow-up, building regs seem to say that baths and showers must have a 50mm depth of seal, so why are so many traps less than this? And is it common to use less?

 

[ShaunCorbs]

You can get shallow seal traps but I would only use one when your limited on height

normally use a 75mm seal trap eg

75mm Seal Bath Trap | McAlpine Plumbing

Optimize your bath drainage with the 75mm Seal Bath Trap, providing a secure and efficient solution for water disposal.

mcalpineplumbing.com

 

[Ben-gee]

You can use the shallow seal traps if the waste goes to a hopper or gully trap, but shouldn’t if going into a foul stack.

 

[flemish4]

Another followup...

I'm looking at using a strap on boss for the 50mm pipe e.g.
FloPlast SP319BL Strap Boss Black - https://www.NoLinkingToThis/p/floplast-sp319bl-strap-boss-black/82795 or Polypipe Black 110mm Strap Boss Side Fixing Clip SG70 - https://www.tradingdepot.co.uk/polypipe-black-110mm-strap-boss-side-fixing-clip-sg70

All of the 50mm waste pipe seems to be solvent weld, but most of the boss adaptors seem to be push fit. It looks like the 32/40mm rubber adaptors might have enough give to accept the slightly larger solvent weld pipe?
But that doesn't look to be the case with the 50mm rubber: FloPlast Rubber Boss Adaptor 50mm - https://www.NoLinkingToThis/p/floplast-rubber-boss-adaptor-50mm/53507?_requestid=491049#product_additional_details_container

So if I was to use a solvent weld boss adaptor ( Polypipe Grey 50mm Soil Solvent Boss Adaptor SW82 - https://www.tradingdepot.co.uk/polypipe-grey-50mm-soil-solvent-boss-adaptor-sw82 ) I don't really understand how this works because it will be trying to weld to uPVC on one side and ABS on the other side! Am I misunderstanding something here? Or perhaps the adaptor is magic plastic that bonds to ABS and uPVC...

And if the existing soil stack (not sure what is there yet - new house) is ABS, it looks like all the strap on bosses are uPVC...

 

[Ben-gee]

You’ll get it in the floplast 50mm rubber, it’ll be tight but that’s what you want.