Shower tray drain extension....

[dc1977uk]

Would the above work? I have an existing long run (about 4m) from the shower drain to soil stack (includes a ptrap and venting). But I want to run the initial waste under the floor boards so I don't have a box running down one side of a wall. Would the proposed drain be suitable in your opinion?
Couple of notes:
1) Drain pipe is currently 40mm diameter
2) The riser where the pipe comes through the floor again in my proposed solution would be accessible (and hidden) - will likely have a screwed top for access.
3) The drop is about 1 in 40.

Appreciate feedback and comments from more experienced plumbers and DIY members please.

 

[denso13]

Poor design, too much of the pipework will be full of water at all times.

 

[dc1977uk]

Thanks denso. Yes there will be some weight in that 40mm pipe, would this fill up with debris quickly, more so than a P trap? The flow is about 15 l/m. Supposing the pipe is properly supported what issues might occur?

 

[oldbutnotdead]

Don't do it, it'll drain very slowly and be prone to blocking in the underfloor section (I had a bathroom sink plumbed in exactly the same fashion. The new visible pipe is not that pleasing on the eye but it does drain properly).
EDIT If that pipe exits to an open hopper it'll be whiffy, if you're really unlucky the underfloor bit will freeze.

 

[denso13]

would this fill up with debris quickly, more so than a P trap

Yes, a shower waste is quite slow running, 2m full of water will block easily. And it is contrary to the regs.

 

[Hugh Jaleak]

Forget it. will constantly block, stink and cause more issues than it ever solves.

What is the issue with running the entire length under the floorboards? Also bear in mind, maximum permitted 40mm waste run under Building Regs is 3m, anything over that and ideally it needs upsizing to 50mm.

 

[dc1977uk]

Thanks all. I won't be going ahead with this and the pipe will remain boxed in. The whole pipe run is actually just over 3m in length but that doesn't change anything.
The weight, smell and prone to blockages is enough to not do this. DIYnot!