help with bathroom waste

[marko65]

I will be starting my bathroom refit next week - would like some views on how to run the waste - have tried to draw a plan showing how waste will run (not brilliantly to scale ) - what I need to know is:

- How should I run the wastes for the basin and shower once they exit the wall - should I join them externally on the run back to the stack ( the basin waste exits the wall at a higher level than the shower waste) or should they join the stack individually.

- Where is the best place for any rodding eyes.

- Can the bath waste join to the toilet waste internally ?

- Someone has suggested that I run the shower waste in 50mm and the basin in 40mm - is this a good idea?

My shower waste is a 90mm high flow shower waste.

I'm putting a new stack in by the way .

Thanks for any help.

 

[Richard C]

Separate connections to the stack are always best to avoid siphoning traps ever time the loo is flushed or the bath/shower is used. I would make separate stack connections for the loo/bath/shower & possibly tee the basin waste into the shower, fitting a small air inlet valve or Hepv0 trap to the basin.

Pipe sizes; you may just get away with 40mm for the shower length but 50mmm is a good idea if you have a high output power shower. Maximum for unvented branch waste runs is 3m for 40mm waste; 4m for 50mm waste; 1.7m for 32mm (or 4m for 40mm basin waste) so I would agree with 40mm for the basin.

I assume you’re running between the joists!

 

[marko65]

thanks for your help richard - looks like I'll be running 40mm from basin, 50mm from shower and joining them on outside wall. I'm now looking at toilet waste running under the floor as well but there is a joist running 80mm from wall so don't know if I can get waste past it - have picked up the pan today and grabbed a swan neck pan connector so I'll see if it will fit later. Am looking at a straight through trap for the sink - I've seen mcalpine ones with or without anti syphon (is anti sypho the same as anti vac?) - is this what I need ? Thanks for any help.

 

[Richard C]

An anti siphon trap is what you need.

 

[marko65]

thanks again richard - my shower waste has a 40mm compression joint - a what point do I change to 50mm ? and once my sink and shower waste meet outside do I then reduce to 40mm on the final bit of run to the stack?

 

[Richard C]

When increasing from either 40-50mm or 32-40mm due to length of pipe runs you should do this as soon a possible after the trap. Run right through to the stack in the same size, don’t reduce back down again or you’ll defeat the whole object of increasing it in the first place.