1 1/4" or 40mm waste

[merseyscouse]

Have just ripped my bath out to fit a shower cubicle, i would like to connect up to the existing waste which is 1" 1/4" (one and a quarter inch)
Bartol, will this be sufficient to drain the tray??
...to size up to 40mm is difficult because the pipes run to an internal stack... but if needs must!!

I was told by a friend that if the waste goes straight into a waste stack then a normal shallow shower waste should not be used...is he correct and if so what trap do i need??

 

[AdamW]

A shallow trap should only be used for a waste going into a gulley. The reason being there is the possibility of water being sucked through from the trap and removing the airlock. Thus leaving you prone to stinky (and possibly explosive) gas in your bathroom.

However, I have a low-profile shallow trap on my bath, going into a 1m length of 40mm waste pipe into a soil stack and have not had any problems with it. No marsh gas leaking into my bathroom yet.

Yes, I would have preferred to have a deep-seal but my bathroom floor is concrete and I had the choice of either jacking my bath up an extra couple of inches or taking a drill to the floor. Neither of which was acceptable.

If the connection between the trap and the stack is dedicated to the shower, i.e. not shared with a bidet that could produce a venturi effect, then you would be OK I think.

 

[AdamW]

Although I have to admit, I have only seen 40mm shower traps so perhaps a 1 1/4" waste is too narrow to sufficiently drain a power shower on full blast.

 

[merseyscouse]

the pipe goes around and under units in the bathroom, it is a wooden floor, can a trap be put 'inline' away from the shower, the waste is only for the shower.

 

[Bahco]

Shallow traps can be used where it is to drain a large surface area such as a shower tray or bath as there is little chance of losing trap seal.
Use 40 mm waste pipe.

 

[merseyscouse]

40mm it is then but will it be ok to reduce to 32mm just before it goes into the soil pipe or would i need to get a some kind of 40mm connector for the soil pipe...space is very tight!!

 

[AdamW]

You might be in luck... if the waste pipe fits onto the soil stack with a push-fit boss.

With such a boss, there is one sized hole whether you are going for 32 or 40mm pipe. Into that hole goes a big rubber bung, the hole in the centre of the bung is sized accordingly for your waste pipe. You can replace the 32mm one with a 40mm one in that instance.

A picture might help. This is the "boss adaptor" (rubber bung)

This is a strap-on boss

Note the hole in the side. It doesn't need to be a strap-on boss to have such a hole.

Anyway, if you have this arrangement you can just whip out the old adaptor and put the new one in.

 

[merseyscouse]

looking at where it enters the stack there appears to be a large knurled nut which i dont want to open yet!!

You might be in luck...

only for bad luck i'd have no luck...LOL