Flexible Drainage Couplings...

[Mulberry View]

I've had to use Flexible Couplings in the drainage run either side of the point that it passes under the foundation, but they just don't make sense to me.

 

 

We aspire to make our drainage smooth and free of undulations, but here the flexible couplings will allow the joint to become misaligned and thus probably create a step or an edge that will undoubtedly catch stuff as it passes over.

 

Have I missed something here? Am I over-worrying?

 

I've done everything I can to ensure the joints are aligned, but by design, this can change if the ground were to move. It frustrates me because I don't actually think they were important in our situation, it's just that the SE suggested them and now the BCO has taken that and clung onto it.

 

Anyone got anything to say about these?

 

 

[SiBee]

Exact problem happens to me on one of our factories! 

I don’t think I have kept any photographs however, the layout of the drain is very, very similar.

About every six months I have to get the drain blasted as it doesn’t take much for stuff to hang on the lip and build up. 

On ours, the fall is very slight and the ground is susceptible to movement. Still not much of lip though but it’s obviously enough. Also, it’s a ladies toilet block in a factory so it sees a lot of “traffic”!!! Why do they use so much toilet roll??😀

Only happens on one of the flexi joints so maybe more of fall/lack of issue.

[Mulberry View]

20 minutes ago, SiBee said:

Exact problem happens to me on one of our factories! 

I don’t think I have kept any photographs however, the layout of the drain is very, very similar.

About every six months I have to get the drain blasted as it doesn’t take much for stuff to hang on the lip and build up. 

On ours, the fall is very slight and the ground is susceptible to movement. Still not much of lip though but it’s obviously enough. Also, it’s a ladies toilet block in a factory so it sees a lot of “traffic”!!! Why do they use so much toilet roll??😀

Only happens on one of the flexi joints so maybe more of fall/lack of issue.

 

I've got two of these, similar but slightly different. The one in the photo, luckily, is immediately adjacent to a rest bend and a vertical stack, taking flow from 2 upstairs bathrooms. The 'matter' will be passing through with some velocity.

 

The other one is slightly less so.

 

It feels like a flaw in the system from the outset.

 

The notion of differential movement in this case baffles me, the drainage is all in the chalk layer. In fact if you lifted the house and foundations away, the drainage would all remain. I don't really see how there will be differential movement in the same way there would possibly have been had I passed through the foundations or wall structure.

[Jenki]

@Mulberry ViewThey call this a rocker joint, the idea being that there is some flex as the pipe passes through the concrete to allow for settlement etc. I agree it doesn't make for a smooth drain. However I was watching a film on YouTube by Wavin, ( it actually had Tony Cottee as a presenter) 

Anyway they used a standard joint either side of the footing, which seems a better solution. Maybe ask BC if this would be acceptable to them?

Found it.

2min 39

 

Edited January 29, 2023 by Jenki
info added

[Mulberry View]

22 minutes ago, Jenki said:

@Mulberry ViewThey call this a rocker joint, the idea being that there is some flex as the pipe passes through the concrete to allow for settlement etc. I agree it doesn't make for a smooth drain. However I was watching a film on YouTube by Wavin, ( it actually had Tony Cottee as a presenter) 

Anyway they used a standard joint either side of the footing, which seems a better solution. Maybe ask BC if this would be acceptable to them?

Found it.

2min 39

 

 

Thanks for that. Very helpful.

 

After challenging the SE over the necessity for a 'rocker pipe' setup a couple of weeks ago, I ascertained that he didn't specifically need the 'full blown' solution and was happy with a flexible joint either side of the foundation in some logical fashion, but didn't need it to meet the 'by the book' spec of a rocker pipe. I asked him what a 'flexible joint' is, he specifically linked me to the rubber coupling I used, he did not mention a normal fitting either side. I am a little annoyed with him if this had been a possibility.

 

This is the view from upstream to downstream, so this is the lip that 'stuff' will have to pass over as it currently stands...

 

 

I say again, this run is contained within the solid chalk bed, beneath the foundation and does not pass through the concrete foundation in any way, so the idea of needing to make it flexible just isn't logical to me, well, here any more any than anywhere else. Why should there be any differential movement here that there wouldn't be under the drive for example? I understand it if the pipe is passing through a wall, but not in isolation completely underneath the foundation.

 

I have to make separate reinforcement over the top of the foundation to deal with any risk of the imposed loads from above irrespective of the above.

[Temp]

Why not rotate it like this or am I missing something..

[saveasteading]

The earth we walk on moves up and down seasonally, but we don't notice. To avoid this damaging buildings we take foundations down to a depth where this is minimal.

Let's look at clay which is most affected seasonally  especially where near trees. Foundations can be quite deep. 

Drains are usually nearer the surface so will rise in winter and fall in summer  more than the building with deeper foundations.

Hence the flexible joints to avoid breaking the pipes. This was more a historic issue, with clay or fibre pipes.

 

If the foundations are shallow then it shouldn't be an issue. The SE can advise and bco should  accept it.

 

I prefer normal pipes but with a flexible filler (eg polystyrene) around them through the wall or footing.

 

In summary, there is good reason for flexible joints but it isn't always the only or best solution.

 

[Mulberry View]

20 minutes ago, Temp said:

Why not rotate it like this or am I missing something..

 

I deliberately orientated the chamber like that, despite it not being my first thought because it it is more logical that way. The flexible connector branch comes in from the 2 upstairs bathrooms, hence it'll see flow from 2 toilets and a large bath/shower. I gave that the priority of the main gulley. The one that comes in from the bottom of the photo is a grey run from the Kitchen, so made sense to me for that to drop in from one of the side ports.

 

Does my logic stack up?!

[Temp]

I think having fewer bends to make rodding easier is more important.

[Jenki]

1 hour ago, Temp said:

Why not rotate it like this or am I missing something..

In my dealings with BC they like the main flow to be on the bottom so that it cleans any incoming from the branches. I don't see any issues with your suggestion, if anything it's removed some 45's so a good thing. It doesn't stop the s**t getting clogged in the joint though.

I tend to think when using the rubber couplers it's better to have a bigger gap between the two pipes i.e. don't try to butt them up. The space will afford some self cleaning.

[Mulberry View]

44 minutes ago, Jenki said:

In my dealings with BC they like the main flow to be on the bottom so that it cleans any incoming from the branches. I don't see any issues with your suggestion, if anything it's removed some 45's so a good thing. It doesn't stop the s**t getting clogged in the joint though.

I tend to think when using the rubber couplers it's better to have a bigger gap between the two pipes i.e. don't try to butt them up. The space will afford some self cleaning.

 

Yes. that I've considered and would be something I'd try to do as a minimum.

 

I notice that Flexseal make a connector similar to what I've used but with an additional metal band across the middle to keep the pipes in alignment, but it's contradictory because it takes the flexibility out of it as far I see.

 

I'm going to arrange an inspection with the BCO, even though my drainage isn't complete. I think to have them on site to discuss is the best way to reach a practical solution.

[Mr Punter]

I only use the band seal couplings on different pipe type and sizes, so plastic to clay, MDPE etc.

[Mulberry View]

On 30/01/2023 at 11:28, Mr Punter said:

I only use the band seal couplings on different pipe type and sizes, so plastic to clay, MDPE etc.

 

Turns out this was the correct answer. My SE specifically suggested the Flexseal type of fitting, but turns out that a normal coupling was actually the right thing to use.

 

So, out came the pea shingle, expanding foam and after a few hours of struggling, I'm much happier.

 

 

BCO came and gave me the green light, so we're all good. Thanks for your input everyone.

 

[Dave Jones]

use a smaller chamber it doesnt look that deep, remove the coupler attached to the pipe coming through the conc and you should have enough room to move/align the chamber and to lose all those bends.

 

If BC still want a rocker connection cut off some of the pipe and move the coupler closer to the conc.

 

you really dont want dogs leg immediately leaving the chamber, may as well do it properly.

[saveasteading]

That is much better. There is still some flexibility there if the chamber drops a tad.