Shower not draining properly

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I've just installed a shower with a shallow trap, and I used the wrong gradient for the waste pipe. It's about 2.5m with a couple of bends, 40mm pipe. I incorrectly thought that 1:40-1:80 would be ok but this is the wrong waste gradient!

In order to achieve 18-90mm per metre I'd have to go throught the external wall and round the corner of the house. This would mean 4 turns rather than the current two, is it worth doing? Also, would using two 135° bends as a pair rather than a single 90° help flow?

Thanks,


Mark
 
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If the shower is not evacuating water sufficiently, of course it is worth doing, if the 135 bends are on the external wall it will run proud of the wall, so best to keep to the 90s.
 
A fall of 1:80 would be okay for a guttering with a small roof, but 1:40 tends to be more normal for most water removal situations. On 2.5mtrs of waste pipe, this would mean a drop of 62.5mm, or about 2.5 inches on the total run, and even 90 degree bends shouldn't cause a problem on this sort of length or drop, so either you've got a very large amount of water being used per minute, or the shallow waste you're using is causing a restriction. I'd be inclined to cut the waste pipe shortly after it comes out of the wall, and see what the flows like - you can join it with a straight coupling afterwards - if it's a slow flow, then look for a different trap that'll handle a high flow rate, and is easily maintainable; if the flows good, then increase the gradient to 1:30, but I suspect it's the trap that's causing the restriction.
 
It may not be pertinent here, but we've had fairly regular problems with the shower, and toilet, not draining properly - it happened last on Christmas day, believe it or not! I should mention that the shower drains into the foul drain from the toilet to outside.

From experience, I have discovered that these blockages probably occur due to there being a 180 degree (yes, really!) bend just after the drain exits the wall of the house. It is underground - under concrete, in fact - and must have been put in place by a cowboy.

Fortunately, I find that if I go outside, remove the vent pipe and push a plunger down the drain a few times, the blockage is shifted. Much easier and cheaper than breaking up the concrete and repositioning the drain.
 
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Um, you can't get a 180 degree bend, that's a straight line. Apart from that, it sounds as though you might have a blockage causing a positive pressure; does the water flow improve after you've cleared the blockage in the drain. If it does, then that's your problem.
 
Um, you can't get a 180 degree bend, that's a straight line. Apart from that, it sounds as though you might have a blockage causing a positive pressure; does the water flow improve after you've cleared the blockage in the drain. If it does, then that's your problem.
You're right, of course. I understood that a 90 degree bend would be a right angle turn in the pipe so, logically, another 90 degrees (=180 degrees) would mean the pipe turns back on itself! Perhaps it's my warped imagination, but wouldn't a 360 degree bend, by the same token, suggest that the pipe does a complete loop and carry on in the original direction? :ROFLMAO:

Anyway, I think we both know what I mean and, as far as I'm aware, doing such a thing is one example of the work being done by a complete idiot. I hasten to add that I didn't do it!

Yes, in answer to your question, the blockage is easily cleared with a few thrusts (ooer!) and the water then flows perfectly. Obviously, something builds up at the (180/360 degree!) bend and, apart from the obvious, I can't think what else could be causing it as my first wife assures me that she never flushes anything naughty down the toilet.
 
I suspect that in your heart of hearts you know where the problem is, but you'e hoping for something a little easier. If the water flows from the shower after you've cleared the blockage, then that's where the problem is. If they've turned the drain back on itself, then you're never going to get a good run, and waste will build up at the end of the run rather than continue round it. it is possible that there's a problem at the return, but only a camera inspection will tell - I assume that there's no inspection chamber above the return to let you watch the flow,

At the end of the day, I reckon you're going to have to bite the bullet, and get the drain redone. You could hire a Kango, and dig out the cement, get a builder in to lay the drains correctly, then fill back in again yourself. Drains aren't difficult, just hard work.
 
Yes, I know where the problem lies and I'm not hoping for an easy fix. I realise that the ideal would be to dig it up and replace it properly, but the 'easy option' is just to leave it and plunge it when necessary. This has happened several times now, but seems to be only once a year or even less often. It was literally a five minute job to clear it, so I'm not really bothered about it. I was just wondering what could be causing the blockages, but it looks like it must be just common or garden poo!
 
I find that 1" per yard is enough. You do not say what yours is or how its distributed. One thing to remember is that foamy water drains a lot slower then clear water.


from this thread :- //www.diynot.com/diy/threads/waste-pipes-gradient-length-and-connection-to-soil-stack.107986/

iirc the Bldg Regs say between 9 and 90mm per metre for falls. Suggest you stick to about 1 in 40 = 25mm/metre = approx 1.5º for soil pipes.

Ensure even gradients, suport to prevent sagging.

Don't drill joists for waste pipes, on the whole.

Take em all outside before joining, wherever practical.

NB shower traps need a 50mm seal, the 19mm ones everyone uses are illegal afaik.
Courtesy of ChrisR
Frank
 
Update to the OP: it turns out that the reason it was not draining properly is because the hopper that the first floor waste pipes go out into was full up as the pipe below it was blocked! I think that the end of the waste pipe being under water (in the hopper) maybe caused an airblock that stopped it draining correctly. It's draining really well now.

On another note, I wonder if the 180 degree bend referred to above is two 90 degree bends together making a kind of dog-leg junction?
 
On another note, I wonder if the 180 degree bend referred to above is two 90 degree bends together making a kind of dog-leg junction?
I'm not sure if you're referring to my query, and I suppose I shouldn't really have interposed on someone else's thread. For that, I apologise.

Anyway, if so, I don't know. All I know is that there is a complete 'half turn' (if that's a better description!), or so said the chap who came to sort it when the problem first occurred. It wouldn't surprise me if it is two 90 degree fittings right next to each other, as I can't imagine that anyone would make a 180 degree fitting anyway, bearing in mind the likelihood of blockages.

I know! Now someone's going to come up with an advert for such a fitting! :LOL:
 
I suppose I could call it a U-bend, but what do I know? ;)
 
pipe size and length is important, fall isn't as critical, also using proper cutters and not having great puddles of glue inside the fitting is important.
 

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