Any plumbers who know about drain flow rates?

19
Found 8th Jan
I have a problem with a linear shower drain I've just installed, they have quoted a drainage flow rate of 45l/m but it appears it's nowhere near that.

Although the pipe diameter of the drain is 50mm reducing to a 40mm pipe - would this affect the water flow much?

I now have the issue where every time I have a shower I end up with a swimming pool, the water does drain, but not fast enough even if I turn the shower flow down.

So I'm going to have to replace the base of my shower which wont be cheap, thinking of taking the drain manufacturers to court to pay as it doesn't do what it says it's supposed to do.
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I'm not a plumber, but surely any bends and turns in the pipe work could alter the flow rate?
Ok. Drain glow rates address as much to do with gradient/fall as much as bore of the pipe. When I did my bricklaying class, we were told that the minimum fall was 10%. If the pipe is not falling fast enough the water will not flew fast enough.
people.wku.edu/tom…tml

If the drain has a 50mm exit and it has been reduced to 40 mm, you have reduced the area of the pipe from 1963 to 1257 mm2 or nearly half.

Add in turbulence at the junction and you have probably reduced the available surface area to less than half.

Unless bald, add in shedding hair and you may well be down further
As mrty says it's down to the fall in your waste pipe - what is it and where does it discharge to? I very much doubt it will be the linear drain.
The drain will be tested with zero external pipework I guess.

assuming that you get 45l/min out and disregarding pipework just looking at a drop in diameter the flow rate would drop from 45l/min to 28.8l/min. May give you an idea if it’s the reduction or pipework bends and drop.
Van19732 h, 39 m ago

As mrty says it's down to the fall in your waste pipe - what is it and …As mrty says it's down to the fall in your waste pipe - what is it and where does it discharge to? I very much doubt it will be the linear drain.


Zero fall - the out from the drain is a fixed straight pipe, which makes it difficult to put any drop in and the pipe that it's connecting to was already 25cm off the ground.
See this link to see what the drain looks like, so if I was to add a drop, the floor of my shower would be a rather large step up(currently 31cm), and I would have to put it in the middle of the shower or at the opposite end for the connecting pipe to drop any amount.

You have to add the height of the drain from the base of the out pipe to the top to get the level that you would walk on.
Bigfootpete12 m ago

Zero fall - the out from the drain is a fixed straight pipe, which makes …Zero fall - the out from the drain is a fixed straight pipe, which makes it difficult to put any drop in and the pipe that it's connecting to was already 25cm off the ground.See this link to see what the drain looks like, so if I was to add a drop, the floor of my shower would be a rather large step up(currently 31cm), and I would have to put it in the middle of the shower or at the opposite end for the connecting pipe to drop any amount.You have to add the height of the drain from the base of the out pipe to the top to get the level that you would walk on.


Unfortunately I think you have therefore answered your own question.

You need to create a fall to get this to drain faster - you will have to redo your shower floor and either (1) raise the shower base or (2) somehow lower the existing drain outlet. Or live with the slow drain!
It’s not the manufacturers fault , you need to do all the prep work before hand and put the correct falls in and then connect the shower outlet .
yozzman123424 m ago

It’s not the manufacturers fault , you need to do all the prep work before …It’s not the manufacturers fault , you need to do all the prep work before hand and put the correct falls in and then connect the shower outlet .


It's not easy when the pipe comes out straight, there's never going to be a drop when it's made like that, even with an elbow (which I do have going down to the drain pipe).
Bigfootpete50 m ago

It's not easy when the pipe comes out straight, there's never going to be …It's not easy when the pipe comes out straight, there's never going to be a drop when it's made like that, even with an elbow (which I do have going down to the drain pipe).



You have to go below the floor boards then. Lowering the pipework
Other option is to put in a sump under the floorboards and a pump/ macerator (you don't want to be lifting the floorboards every 6 months because of a hair and soap ball).
Edited by: "mrty" 8th Jan
mrty1 h, 9 m ago

Other option is to put in a sump under the floorboards and a pump/ …Other option is to put in a sump under the floorboards and a pump/ macerator (you don't want to be lifting the floorboards every 6 months because of a hair and soap ball).



Not sure I’d want to be messing round getting power to the pump etc and replacing that when it fails for the sake of a few floorboards. Much easier to chuck some chemical unblocking solution to save lifting the floor boards.
Bigfootpete7 h, 35 m ago

Zero fall - the out from the drain is a fixed straight pipe, which makes …Zero fall - the out from the drain is a fixed straight pipe, which makes it difficult to put any drop in and the pipe that it's connecting to was already 25cm off the ground.See this link to see what the drain looks like, so if I was to add a drop, the floor of my shower would be a rather large step up(currently 31cm), and I would have to put it in the middle of the shower or at the opposite end for the connecting pipe to drop any amount.You have to add the height of the drain from the base of the out pipe to the top to get the level that you would walk on.



25cm off the ground? nearly 10 inch already is a big step up,
these guys are talking about the fall of the drain pipe this drain attaches to, running the 3-4 inch straight won't make much diff if it falls away neatly after that. obvs any curves/elbows horizontally in the run will cause slowdowns as well.
Is the Soil (big vertical) pipe outside the house? Can you go through the wall and create the drop? If so, maybe you can get rid of the platform the tray sits on. Even if its inside, can you go down into the room below and box in the 2" pipework?
Dannyrobbo17 h, 40 m ago

You have to go below the floor boards then. Lowering the pipework


I'm on the ground floor - so solid concrete underneath.

ccnp2 h, 35 m ago

Is the Soil (big vertical) pipe outside the house? Can you go through the …Is the Soil (big vertical) pipe outside the house? Can you go through the wall and create the drop? If so, maybe you can get rid of the platform the tray sits on. Even if its inside, can you go down into the room below and box in the 2" pipework?



No - soil pipe is inside, I considered replacing the pipe with a 50mm one, most likely will require removing the bottom porcelain tile that is right next to where the pipe goes into the wall where the soil pipe is (that could be tricky removing that without damaging surrounding tiles).
I'm going to get a plumber in to see what they can suggest.
Bigfootpete12 m ago

I'm on the ground floor - so solid concrete underneath.No - soil pipe is …I'm on the ground floor - so solid concrete underneath.No - soil pipe is inside, I considered replacing the pipe with a 50mm one, most likely will require removing the bottom porcelain tile that is right next to where the pipe goes into the wall where the soil pipe is (that could be tricky removing that without damaging surrounding tiles).


Bigfootpete12 m ago

I'm on the ground floor - so solid concrete underneath.No - soil pipe is …I'm on the ground floor - so solid concrete underneath.No - soil pipe is inside, I considered replacing the pipe with a 50mm one, most likely will require removing the bottom porcelain tile that is right next to where the pipe goes into the wall where the soil pipe is (that could be tricky removing that without damaging surrounding tiles).



Well then you must raise the shower platform then. That’s all your plumber will suggest I imagine
Dannyrobbo9th Jan

Well then you must raise the shower platform then. That’s all your p …Well then you must raise the shower platform then. That’s all your plumber will suggest I imagine


I'm 6'3" - I've a got a rainfall showerhead - I wouldn't be able to fit underneath it.
Bigfootpete1 h, 0 m ago

I'm 6'3" - I've a got a rainfall showerhead - I wouldn't be able to fit …I'm 6'3" - I've a got a rainfall showerhead - I wouldn't be able to fit underneath it.



Your Height is irrelevant you need water to be drained, we are not talking raising it a foot but just enough to . You either need to raise the shower because you can’t gravity drain properly with a level pipe Or you pump it away.
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