Bath and basin waste combined on new build

[Mgrant]

Hi if combining a bath and basin waste on a new build should you really run 2 inch and reduce to 1.5 inch after the tee to the basin?

 

[stevetheplumber]

shouldnt realy be combining them but new builds dont seem to worry about it, yes to pipe sizesi would run it all in 2 inch and reduce close to bath and run 1.5 up to the basin reduce close to trap

 

[Staffy85]

you could run 2" , i would just use 1 1/2" then reduce to 1 1/4 on the elbow comming through the stud or what ever to basin, you might need an anti vac trap on basin,

 

[AWheating]

It's not ideal but sometimes builders put soils into stupid places and bossing 2 wastes out can be impossible. You can consider short boss in soil boxing and run up into floor? Either way stick to max lengths for each size.

 

[Mgrant]

Thanks what about combining a basin and shower waste as long as there's an anti vac trap on the basin is this usually ok?

 

[JCSPLUMBING]

I would really try to separate them if possible. It rarely works well, joined together. Always blocks up and loses trap seals

 

[Mgrant]

even if both have anti vac traps on?