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Why is it that if you want a slim stone resin shower tray (under 50mm) you can have a 90mm fast waste, but if you buy a "standard" deep stone tray say 80-100mm deep you can only get a 50mm waste?

 

Is there any solution to prevent me paddling (deep) or letting the water almost overflow the tray (slimline)?

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Firstly, why would you consider a deep tray? They’re not exactly ‘beautiful’.....

The litres per minute discharge rate is what usually dictates the size of the waste. A slimline tray is deemed more likely to need efficient means of discharge, hence the larger diameter, but the deeper trays can use a bit more gravity to get rid of water.
Suds are the nightmare so cause most issues, but make sure the traps regularly cleared out and you should be fine. 
To be honest, if the waste pipe work is in 50mm instead of 40mm ( 2” instead of 1.5” ) then that will pay huge dividends. 50mm gives a decent air break ( air can travel back up the pipe over the discharged water travelling down it giving relief from any vacuum happening ) and is something I practice without exception.

Taking the chrome cap off the shower waste will also show how badly the suds stop natural discharge. 

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Some 50mm traps have better flow rate than some 90mm traps...

 

McAlpine have 90mm traps rated 24, 34, 26, 42, 50 L/min and 50mm traps rated at 40, 50, 54, and 56 L/min

 

Yes I do have that the right way around!

 

https://mcalpineplumbing.com/traps/shower-traps-accessories

 

One issue is that many traps have a small Euro spec pipe coming out (38mm?) and a 45 degree adapter to suit UK pipe sizes (approx 40 or 50mm). So there is an inherent restriction compared to others.

 

Note that (no?) 50mm traps are top access so you need a plinth with 50mm traps. 

Edited by Temp

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I approached this by measuring the shower flow rate at our old house, which we were happy with, deciding to use the same for the new house, and then looked at the waste size needed for that and concluded that even 24l/m was a massive overkill.  I fitted a 90mm McAlpine top access trap, that had a 40mm outlet, so I used a straight ~2m run of 40mm pipe to the top of the soil pipe stack.  In practice, the biggest flow restriction seems to be around the periphery of the lid bit.  Doesn't take much in the way of soapy stuff to slow down the flow around that narrow slot.  The 40mm pipe easily copes with our ~10l/m shower.  Biggest nuisance is cleaning the lift out top bit, which is a bit of a fiddly job.

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I just fitted a wall drain it came with a 50mm outlet.

 

Nick said 50mm waste from there on.

 

Job done! 👍

 

Nothing will impede the waste flow like having two women in the house with long hair. Wish I'd married Sigourney Weaver. 

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I realise that different things can be done to try overcome the problem, it just seems bizarre that the 90mm waste is only on the slimline trays.

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Perhaps the rational is that people who buy tall trays don't care about height so don't need top access traps.

 

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There are loads if top access 50mm traps, so not sure it can be that

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On 22/02/2020 at 16:48, Temp said:

Note that (no?) 50mm traps are top access so you need a plinth with 50mm traps. 

I’ve never seen a shower trap that isn’t top access 🤔. The grille on the top usually needs a tool, like a crotchet hook, to remove that part but they have bucket sieves inside in most cases where that catches the worst of the hair / other. 
FWIW, some don’t appear to be serviceable, but are.

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Could you drill a deep shower tray and fit a 90mm waste?

 

Don't knock a deep shower tray. In our house the upstairs ensuite tray served as a defacto mini bath when the youngest was very small. (Cos we had no bath for a short while 😉  )

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Guess I was wrong about 50mm traps. I didn't think you could remove the water seal tube through the top on those.

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Hi, I  hope it's ok to add to this thread.

 

I've been reading this forum for a while now and trying to learn and remember things to help with my barn conversion build. 

 

It's often advised to install 50mm pipe, and Mcalpine traps are recommended. I've installed the 50mm pipe but am now struggling to find a 90mm top access trap with 2" outlet, they all seems to be for 1.5" pipe. Could anyone link to one please?

 

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I assumed that having 1.5" outlet on the trap would remove the advantages of fitting 50mm pipework. Is this not the case?

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19 minutes ago, Jenni said:

I assumed that having 1.5" outlet on the trap would remove the advantages of fitting 50mm pipework. Is this not the case?


Not at all - it may be slightly slower but will clear much quicker once into the 50mm section. 

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