Best flow option for shower tray and waste?

[imsparticus]

I'm looking into installing a new shower which is on a long run to the stack. I would like to go for a belt and braces approach as much as possible and was wondering what the best options were for the tray/waste and waste pipe diameter etc. To get the required drop on the run I have no option but to raise the tray on a plinth.

I have noticed that all the shower trays seem to have a 40mm outlet/trap if they are deep ones and 90mm outlet/traps on the shallow ones.

I am planning on using 50mm waste pipe from the trap to the stack but would it benefit from an aav and if so where would this be best placed? How much better are the 90mm traps compared to the 40mm taking into account the deep trays would give me a better chance to turn off the shower before flooding the bathroom if there is reduced flow due to the trap needing cleaning etc.

Many thanks.

 

[Dodgemonkey]

What's the length of the waste run? On 50mm you'll need a fall of min 18mm/m. There's a theoretical max run of 3m using 40mm waste, and I'm assuming that it won't be any more than that using 50mm. I don't know for sure, but could the trap itself be supplied with an incorporated air admittance device? I've seen the very same thing on bath traps...
Good luck with it,

Mike

 

[imsparticus]

Thanks for the reply Mike. The run is around 6 meters, so from what I’ve read I will need to install an aav. Had a quick look for a trap with an aav built in but as you say these seem available for bath wastes but I'm yet to find one for a shower waste. I'm happy enough to use one of the smaller aav's i.e. 50mm and run it up behind a stud wall into the loft if that’s what it would need.

But the question remains what type and size of outlet on the tray would flow the most taking into account the shallow trays would be much quicker to overflow if there is a blockage. Ideally I would go for a deep tray with a 90mm trap but I can’t seem to find any.

 

[Dodgemonkey]

Wow, that's a long run, and would call for over 4" of fall to drain effectively. Probably not unheard of before though. I wish I could help further, but my knowledge is fairly limited in this area.
As for traps, just looked up a 90mm - "Typhoon Vortex", sounds like it works extremely well. Claims to drain as much as 36 litres..?? per min.

With the length of run I'd be inclined to give what extra help I could, so your plan to run an air admittance device upwards discreetly sounds good.

Hope it works out ok.

Mike