Slight reflex angle in foul drain run.

[MikeSharp01]

I am just creating the ground works for our plot and we need an access point on the boundary. Problem is one of the flows will come in at 80° to the flow. I think that is called a reflex flow. I have to build the chamber based on existing run, see photo (white mark is chamber center). I was just going to slipper bend and flaunch it in but I could put a shallow bend a few mm back then slipper bend and flaunch it into the flow but this will mean my otherwise dead straight 12m run will no longer be straight. The slipper will turn it probably 45° which is about the angle of a standard plastic chamber. Any thoughts?

[PeterW]

What's the direction of flow ..??

[MikeSharp01]

Sorry along the black pipe right to left out of our property as you look at the photo. Lucky for us we are the end of the run so I can tinker a bit. 

[Mr Punter]

Come in at the side of a 5 inlet chamber and use an 11deg or adjustable to make up the difference

[MikeSharp01]

Thanks @Mr Punter but I am not sure I get a prefabricated chamber in as the invert drops on the angled entries in them are so high I won't get 1:80 to arrive at the existing pipe high enough, I have only 64mm diff at the end of the pipe at 1:80, so will have to cut into the pipe I think and flaunch it in with a sharp sand / cement mix then build the chamber around the whole pangangle and pop a rectangular lid on it! I think the workmanship should be OK but as the sewer run is common to several houses below us on the road I guess I have to work with BS EN 13598 / SFA7. The OSMA chamber has 60mm but the drop across the chamber is more than the exiting pipe so that also seems like a non starter. I will have a look at SFA7 if I can find a copy on-line.

[Oz07]

How deep is it? You can get level invert chamber based in the small ones (320? Dia)

[PeterW]

Are you first in the run then or is that a common sewer ..? First in and you can do what you want within the building regs as it's your pipework. 

 

Any way you can pull the rest of it up and move the chamber down the run slightly ..? Then the upvc intercept would be easier. 

 

I'm pretty sure that any built up chamber still needs a half pipe joint in the bottom and you can't build it up from sand and cement but would need to check. 

[MikeSharp01]

Have had a look at SFA7 and as you @PeterW says we are the end of the run so the pipe up to our boundary is our responsibility alone. (see this link Southern water - our area but looks like a national thing.) Phew... I say as I have already been working elsewhere on the run blocking - I did check we were the end of the run first, it off etc as part of the demolition work. I will need around 800mm depth @Oz07on the chamber to the finished path surface its sits along. If I measure with extreme care I can just get the 450mm OSMA chamber in with 1mm clearance looking at the CAD drawing of the part. If I form my own chamber its all about using a slipper bend on the end of the run and forming it into the existing pipe. There will be two further runs but they come in directly along the line of the exiting pipe and at 25deg (below the black pipe in the photo) to it so although one will be easy the other will need a bend at the end of it to match to the 45deg inlet.  I guess the chamber will be simpler but it does mean I will have a step change in diameter, the black pipe is 135mm external / 115mm internal, this looses me another few mm of height which to my mind makes the OSMA option very marginal or won't a coupel of mm here or there make any difference given the rush of 'stuff' for want of a better word is falling through 60mm+ as it enters the main run. As one of my neighbours said the other day, 'you are spending too much time thinking about it' - helpful soul!

[PeterW]

2 minutes ago, MikeSharp01 said:

. I will need around 800mm depth @Oz07on the chamber to the finished path surface its sits along. If I measure with extreme care I can just get the 450mm OSMA chamber in with 1mm clearance looking at the CAD drawing of the part.

 

Confused...? Where are you measuring the clearance..? Vertically..?

[MikeSharp01]

Yes, sorry vertical heights. The run invert will arrive at the black pipe 64mm, at 1:80 from the chamber 13m away (it passes through a small chamber halfway sop as no to breach the 12m rule on length of run without access), above the invert of the black pipe at the white marker on the black pipe. So I have just 64mm to play with. The OSMA invert change from the main run to the 90deg inlet is 60mm but the difference in pipe diameters between 110 (outer) and 115 (inner) is means .... I will draw a picture!

[MikeSharp01]

Picture as promised: (I think my fixation with mm and fractions thereof is not helping )

 

Edited June 14, 2017 by MikeSharp01
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