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As part of a bathroom refurbishment I'm installing a new low profile shower tray and a 90mm waste. I'm looking to use a McAlpine 1.5" hi flow shower trap, which gives 42 l/m flow.

There are various flanges available, but the one that would appear to give the best flow is the ST90CB10-HP2:

1581946298981.png

However, the flange on this looks to be proud of the shower tray and so isn't ideal if positioned where someone might be standing, therefore I would prefer the ST90CPB-S-HP2, which has a slotted flange that looks like it will fit flush with the shower tray:

1581946399186.png

Does the flange type make any difference to the flow rate?

I would be interested to know which of these models is the most commonly used/installed by you guys.

Thanks.
 

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I can understand why the ST90CB10-HP2 version isn't load bearing as this sits above the shower tray. I guess it would be uncomfortable to stand on it.

However, the other is a chrome plated brass flange that sits on top and flush with the shower tray as far as I can see, so I wouldn't think that would be a problem to stand on. The shower tray would take most of a persons weight anyway.
 

rpm

Esteemed
Plumber
However, the other is a chrome plated brass flange that sits on top and flush with the shower tray as far as I can see, so I wouldn't think that would be a problem to stand on. The shower tray would take most of a persons weight anyway.
Sounds like you have a clear winner then.
 
Sounds like you have a clear winner then.
Not really, as this doesn't answer the question about flow rates!

I also contacted McApline and received the following reply, which confirms my understanding of the slotted flange fitting flush to the shower tray, but I'm surprised they don't know what the flow rate is of their own flange:

"With reference to the undernoted we confirm that the flange on the ST90CPB-S-HP2 will fit flush with the shower tray but we do not have available the flow rate for this particular flange but obviously it will be greater than 26 litres per minute which is the standard.

We are not sure that you are concerned about someone standing on the ST90CB10-HP2 is warranted as the trap is usually in the corner of a shower tray and people are unlikely to stand on the flange.
"

On their webpage for this shower trap they only mention a flow rate of 42 l/m. It does surprise me they don't include flow rates for the alternative flanges if they are different to this!

As much as I prefer the look and fit of the slotted flange, I'm purchasing this particular shower trap for the flow rate and don't want to compromise on this, so still a little confused.

Does anyone have experience of installing these shower traps that may be able to offer some advice?
 
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Just how many L p/m does the shower kick out then!
The digital shower has two heads (fixed and slider) and is capable of producing 16 l/m at 1 bar.

It's a good point as I'm probably worrying about nothing with even 26 l/m as seems to be the "standard" according to McAlpine.

I just want to be sure as once it's installed, it's not coming out again and it will be difficult to test both shower heads without soaking the immediate area.
 

Stigster

Esteemed
Plumber
I have done a calculation based upon a 42mm waste pipe, 1.7 metres long with a 20mm fall. Assuming that the grate on the waste pipe has an open area equal to or greater than the pipe, I get a flow rate of 54.4 litres per minute.

I think you'll be fine with it.
 
I have done a calculation based upon a 42mm waste pipe, 1.7 metres long with a 20mm fall. Assuming that the grate on the waste pipe has an open area equal to or greater than the pipe, I get a flow rate of 54.4 litres per minute.

I think you'll be fine with it.
Thank you Stigster, that is good to know.

The waste pipe connects to a soil pipe about 2 metres from the point at which it pops out of the wall.

McAlpine have confirmed that the flange used on these traps doesn't make any difference to their flow rates, so I will be going for the slotted version.
 

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