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Discuss Low profile shower trays and flow rates in the DIY Bathroom Remodelling Advice area at PlumbersForums.net

I’m considering the JT40 shower tray, along with the matching JT90 trap. Their blurb states it can shift 48 litres / min.

Looking at the flow rate for a Grohe bar shower, for example, it’s quoted at 26 litres / min at 3-bar and this is approximate to what my pressure is and my flow rate is above what the shower can output and so no issue there.

So, if i understand correctly, i should have no issue with drainage (i.e. pooling / overflowing), as the tray / trap exceeds the output of the shower!? Am i missing anything obvious?

i’m just slightly wary of low profile trays and whether i am asking for trouble by installing one? The previos tray was much deeper, but only had a 50mm trap. What are people’s experiences of such trays or specifically, the JT40?

TIA
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I forgot to add, but I spoke to JT today about this and they recommended their JT40 for higher flow rates, over the Merlin / Ultracast range. I assume this is because whilst the other trays are much deeper, they only have a 50 mm trap.
 
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Ben-gee

Esteemed
Plumber
Look, 95% of trays installed now are low profile- if done properly there will be no problem. I know we are not ‘engineers’ but do you really think an entire industry would produce and regularly install something that didn’t work?

Ok, no one mention push button toilets!!!!!!!!!!!
 
Look, 95% of trays installed now are low profile- if done properly there will be no problem. I know we are not ‘engineers’ but do you really think an entire industry would produce and regularly install something that didn’t work?

Ok, no one mention push button toilets!!!!!!!!!!!
I wasn’t suggesting that they don’t work, but questioning how well they work.
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I wasn’t suggesting that they don’t work, but questioning how well they work.
Thanks for your input
Post automatically merged:

I wasn’t suggesting that they don’t work, but questioning how well they work.
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Thanks for your input
...and primarily whether my logic is correct?
 

snowhead

Esteemed
Plumber
I've no experience of that tray and trap but the logic is correct.
The flow rate of the trap exceeds the flow rate of the shower so there should be no build up in the tray.

BUT,,
The flow rate of the trap is only as good as the pipework leading away from it.
Avoid Flexible pipes in the waste and too many fittings and 90 deg knuckle elbows (use slow bends).
If it's going any distance, increase the size of pipe.

More bends and length of pipe = more resistance and less flow.
 
I've no experience of that tray and trap but the logic is correct.
The flow rate of the trap exceeds the flow rate of the shower so there should be no build up in the tray.

BUT,,
The flow rate of the trap is only as good as the pipework leading away from it.
Avoid Flexible pipes in the waste and too many fittings and 90 deg knuckle elbows (use slow bends).
If it's going any distance, increase the size of pipe.

More bends and length of pipe = more resistance and less flow.
Thanks @snowhead for confirming my logic and i take your point about what goes on beyond the trap.

I’m always wary of manufacturer claims, which rarely live up to expectations in the real world. Would hate to find out the hard way, upon first use! I take BG’s point though about their widespread use.
 

Ben-gee

Esteemed
Plumber
The jt4o is as good as any other, should be at that price.
In my experience they are fine, do a drainage test before you tile. All of these trays benefit from clearing out the trap frequently, I do ours weekly, luckily the design makes this very easy to do - and they look so much smarter than the deep trays.
 
The jt4o is as good as any other, should be at that price.
In my experience they are fine, do a drainage test before you tile. All of these trays benefit from clearing out the trap frequently, I do ours weekly, luckily the design makes this very easy to do - and they look so much smarter than the deep trays.
It certainly ain’t cheap, but i’ve seen a lot of positive reviews about them and they are stocked at my local Wolseley. As such so i won’t have to pay postage and if there are any problems, it’ll be an easy return.
i agree they look considerably better than the chunky monkey such as the Merlin / Ultracast.
Cheers
 
For a cheaper reliable alternative look at MX Elements, nowt wrong with them.
Thanks for the suggestion and i have looked at them already, but the problem is that i need either left or right corner for the trap and they are all centred on the long edge. I’d have to then go through a joist and also break into the wall downstairs to drop the height if the soil pipe. :-/
 
K, i’ve spent time today checking straightness of walls in the recess where the tray will reside, along with pipe positioning. Whilst all less than ideal, i can make it work.
My issue and hence question, relates to the positioning of the trap. Ideally i need the trap on the left-front side, but most trays (900 x 800) have them on the right and some in the centre; centre is a no-goer. What i’m not sure about therefore, is how difficult it will be to fit the trap and make it watertight, if it is (essentially) againt the back wall i.e. opposite side to the front access (riser) panel?
i’ve seen many comments about the fun that can be had trying to seal these things and i imagine it is doubly difficult when done at arm’s length, with limited access. Having never fitted one, i don’t know what to expect i.e. is it a doddle, or a serious PITA?
Not finished searching for trays yet, but another option maybe to drop to a 900 x 760 tray, if it is inadvisable to have the trap on the far side; the assumption being that i may find one with a trap on the RHS.
Any advice will be much appreciated.
 
Don’t worry, if you have everything lined up, it’s a piece of pi55.
Thanks for confirming. So, should i mount the trap on the pipework, drop-in the tray and then draw the trap onto the underside of the tray with the aid of the trap cap? As you would do if it was a floor-mounted tray? Can’t imagine i’ll be able to manipulate the pipework into the trap once the tray is down, even with a riser kit (with trap on RHS).
I note that the manufacturers usually state not to use any sealant on the underside of the traps and yet many forum comments say the opposite. Is the best approach to start with no sealant and it if doesn’t seal, add some?
Cheers
 

Ben-gee

Esteemed
Plumber
Everyone I know that does this for a living would use silicone on the rubber seal, despite what some manufacturers may say.
You should be able to add this once the tray is in position, as access is possible through the 90mm trap hole.
(Tip, run a thin bead of sealant on the underside of the trap seal to hold it in place so you don’t knock it off and lose it under the floor as you manoeuvre the tray into place.)
 

WC1

Gas Engineer
I dislike low profile trays especially in rented properties, tenants (bless 'em) just don't notice the water filling the tray and leaking out. They are in my mind a proper example of form over function (except where there are disability / elderly residents)
It's so hard to find a good range of "proper" height trays.
 
I dislike low profile trays especially in rented properties, tenants (bless 'em) just don't notice the water filling the tray and leaking out. They are in my mind a proper example of form over function (except where there are disability / elderly residents)
It's so hard to find a good range of "proper" height trays.
Thanks for your comment.
Why would they fill-up though if the output of the shower is less than the tray / trap can shift, unless the trap has not been cleaned?
 

Ben-gee

Esteemed
Plumber
That is what he means, the tenants don’t keep the trap clear- then they fill up and overflow.
As I say I clear mine most weeks as it gets a lot of use (often six/seven showers a day)
 

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