Slight backfall on short 32mm waste stub into bottle trap

[john2k]

I have a 32 mm waste pipe solvent welded inside a stud wall, with a short stub (about 15–16 cm) projecting out via a solvent to compression adaptor. Everything inside the wall has correct fall, but I’m slightly concerned the short projection may be level or very slightly falling back toward the trap.

The bottle trap sits lower anyway, so worst case any water would just sit in or return to the trap. The compression joint will be accessible. Is this acceptable in practice, or worth worrying about?

 

[terryplumb]

A slight difference in height isn't great ,but unlikely to cause much grief

 

[john2k]

A slight difference in height isn't great ,but unlikely to cause much grief

I tested it by running water through a temporary hose with a funnel into the stub. Water only came back when I stopped pouring and withdrew the hose, not while it was flowing. From visually checking it again, the short stub looks dead level or at most very slightly back toward the trap. I will measure it or use laser level to try and see if it’s dead straight or if it’s falling back towards the trap.

I’m thinking to make a short elbow piece with a spare solvent elbow I have and fit it with the rubber compression ring and pour water down the temporary vertical run that elbows to the compression wall fitting and then about 10mins later remove the fitting and see if water comes out? Or is it not needed?

 

[foxhole]

Is the basin is draining? Then as they say , if it ain’t broke don’t fix it.