Shower Waste - cutting it down?

[Craka]

The old bathroom had a shower with a acrylic base that fed into this waste pipe.
I'm not putting a base in and will be screeding a shower floor. Can I trim this waste down where the red line is to fit puddle flange lower then where this current waste height sits?

[r3nov8or]

If cut down that far, test that you have enough clearance within the pipe bend to take the puddle flange. My other concern would be if there is any give in the PVC pipe and the very thin screed over it, may lead to the screed cracking and the waterproofing being compromised

[droog]

Main concern would be potential for water backed up in the pipe or even splash coming out between the puddle flange and the pipe.
You may be better to chase the pipe down at the next bend and drop the whole thing down.

Agree with comment above about floor thickness above the pipe, but depends on what your puddle flange is and its depth.

Better to do it now while its all open than have problems later and have to rip up the finished floor.

[Craka]

I see what you mean as far as cutting that lower with potential water come back up and out. Trying to avoid cutting into the slab, if I screed to the height is now would that be viable option with leaving a thick enough screen over the pvc pipe?

[r3nov8or]

Just dawned on me. What's the size of the pipe? Looks bigger than required. If so, a little work where it rises from the slab and it could be reduced to 50mm for a suitable puddle flange, and gives you heaps of room over it for the screed. And you may choose to move it's final position, even directly over the slab riser.

[r3nov8or]

I see what you mean as far as cutting that lower with potential water come back up and out. Trying to avoid cutting into the slab, if I screed to the height is now would that be viable option with leaving a thick enough screen over the pvc pipe?

If you leave everything as is and work to the current height I think that'll be enough for a stable screed. A mesh reinforcement would give more peace of mind