inspection chamber and pipe gradients

[sm_jamieson]

I've set out the main part of my drainage, being old clay to new inspection chamber to rest bend and soil pipe etc, with the gradient at 1 in 40. Two other connections on the chamber are to connect to two roddable bottle gullies (one under outside tap, other for rain water runoff - combined sewer). If these gullies are connected to the chamber mainly with straight pipe, the gradient will be a lot steeper than 1 in 40. Is this OK, or do I need to use some kind of rest bend from the gully so that the main run of pipe from gully to chamber is about 1 in 40 ? Of course, if the roddable feature is to be any use, then run needs to basically be straight. Thanks, Simon.

[dennis]

Where do they still allow rain water to be connected into foul drains? You could be in serious trouble, you would be around here.

[Roger Mills]

Presumably everywhere where there is a combined sewer rather than separate sewers for foul and surface water.

[dennis]

Like I said where? AFAIK its been made illegal. They certainly should be as they overflow in storms and flood places with raw sewage.

[sm_jamieson]

I said its a combined sewer. Coventry. Never had any problems in storms. Most of the 1930s houses are like that. AFAIK, most houses with hoppers for bath water have combined sewers. Soakaways would be no good - there's a great thick layer of clay. There is no separate drain for us to use ! Connects straight to a public sewer running though the back gardens. Got me thinking though - the road drains going into the same sewer would seem a bit odd, but I guess they must do. Simon.

[Andrew Gabriel]

Just about every older dense urban area, where there's no separate rainwater drainage system and nowhere to put soakaways.

You can ask for permission anywhere. A friend of mine had no problem getting permission out in a rural setting, which did surpise me a bit.

[Roger Mills]

It may be illegal for new build - but the idea of having separate sewers is fairly recent (1960's?) and lots of places built prior to that have only a single, combined, sewer.

Regulations like this are not usually retrospective. Do you honestly think that the powers that be are going to make you build an additional sewer in existing densely populated areas? The implications of doing this - *and* of separating the two types of output from *each* property are horrendous.

[Phil L]

The '1 in 40' rule only applied to soil - rainwater can go at any angle, but even soil drains are now no longer subject to the '1 in 40' rule.....the idea was that shit, travelling at velocity, would splatter up the sides of inspection chambers and the like, then when it set, it would build up into a blockage, they now don't insist on this as slow moving turds cause blockages themselves.

[Chris J Dixon]

I thought the justification was that if the angle is too steep, the fluids drain too fast, leaving the solids stranded. A lower angle was thought to keep the solids afloat and moving.

Chris

[sm_jamieson]

Thats what I thought too. Anyway, this does not apply to water only, so I guess I can put in any angle I like. But I'll be prepared for the BCO to shout at me ! Cheers, Simon.

[Jim Alexander]

Coming in late but puzzled. You can only put in an angle accomodated by the inspection chamber socket and or the gulley outlet. So why not create the gradient to suit the inspection chamber socket by a short bend and pipe extension at the gully. Or am I missing something?

Jim A

[sm_jamieson]

The roddable gully has a side-exit socket at I guess 87.5 degrees. The inspection chamber has 20 degree adjustable angle inlets (flopast from screwfix), and you are allowed slight bends near roddable points (inspection chamber and roddable gully). You are correct, there will almost certainly be some slight bends to allow the main length of pipe between them to be straight. All this is a given.

The point was, if I use any more than a slight bend from the roddable gully, the roddable feature will be useless, since any tight bend just after the roddable gully would prevent rods entering the main pipe. In this case a nomal trap and separate rodding eye would be required.

The question was, (1) between slight bends at each end and the main run straight at a steeper angle, OR, (2) tighter bends at each end and the main run straight at a shallower angle.

If I create the gradient to suit the sockets, I will end up using scenario (2) above. Of course this is mitigated on the chamber end by the adjustable inlets !

Hope that clears things up ! Simon.

[Doctor Drivel]

Having solids move away too fast can drag the water out of a toilet, and other, water traps. Look at external stacks. The toilet goes outside, and an immediate near horizontal elbow and then tees into the drain stack. The toilet does no go directly into a tee on the stack. The elbow reduces flow.

[Jim Alexander]

if you value rodabilty ahead of gradient have a look at the Marley compact gully which has a 45deg outlet.

Jim A