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                                                                                                                                                                 Last updated 7 January, 2014 > site map > drainage bends                                                    

Drainage Bends

Simply enough these are the changes of direction on a drainage system which are usually available from 11 ¼ to 90 degree in most materials, long and short radius bends are available and they can be plain ended as shown below left (clay) or single or double socket (underground plastic).There are also adjustable bends available in plastic that allow you to achieve 0 to 30 degrees of turn.

They are just as prone to defects such as root ingress or damage due to vehicular movement as any other part of a drainage system, they are however more prone to internal damage from over zealous rodding or jetting particularly the sharper bends are constructed from clay.

www.draindomain.com_drainage bends drain junctions and bends

You tend to find that the older clay systems were made up of 30, 45 and 90 degree bends with anything less being accomplished by opening up the joints slightly on straight sections of pipe work, because the joints were sealed with sand and cement it was easy enough to slightly off set each pipe and still maintain a water tight joint. As a result when you excavate and remove an old clay system you can be left with a conundrum when trying to match up your angles, particularly in a small and confined dig.

Another favourite trick used on the old clay systems would be to use a junction instead of a bend with the unused upstream collar being capped off with a piece of slate and a mortar plug as shown in the image above right, often used where a 100mm branch line meets a 150mm main line as it not only saved using a bend it also saved the additional cost of using a 100mm to 150mm adaptor pipe

Drainage Building Regulations

Modern building regulation require that the entire drainage system to be accessible for cleaning and maintenance and this often requires an access point at the point of a sharp change in direction, the preformed plastic manhole basis are available with 90 degree channel bends as well as 45, 30 and 15 degree channels.

Rest Bends

A rest bend is in affect a 90 (or 87.5) degree bend usually situated at the base of a soil vent pipe, a drop shaft or beneath a downstairs toilet, the main difference from a standard 90 degree or quarter bend as they are also known is that they are long radius and they have a foot or support fin on their base. This is to help absorb the force of the flushed water as it hits the base of the bend and they would usually be installed on a bed of haunched concrete. In reality most rest bends are just a plain 90 degree bend with no special attention given with regard to the impact of the flushed water or for the additional support required beneath the bend itself, occasionally we will find a concrete base or a couple of bricks offered as a token gesture.

Rest Bend Problems
drainage rest bend

These bends are prone to root ingress mainly because they extend up to ground level, shallow root systems will work their way through disturbed ground such as a driveway sub-base before entering the system and growing down into the main line drainage.

The collar at the point that the clay drainage meets the cast iron vent pipe is also a weak point as it can often be just above ground level and open to impact and frost damage, many of these collars are broken when the original cast iron soil vent pipe has been replaced in plastic and we have found many a broken bend the result of over vigorous rodding from a DIYer.

As already mentioned these bends do take a pounding with the steady and constant flow of water passing through them and as a result there will usually be water loss from at least one joint, this water loss into the sub-soil then undermines the bend or the half brick supporting it causing further movement and more water loss, and so it goes on until the lot collapses.

Even if the guy who installed your system went belt and braces and installed a proper rest bend bedded on a concrete pad we still find that the first pipe downstream of the bend can settle and snap adjacent to the rigid construction of the rest bend, this is usually due to vehicle movement or simply because there was no specification for pipe bedding on the rest of the clay drainage system downstream of the soil vent pipe.

The problems these defects bring include blockages as paper and solids snag in the system, the water loss can undermine house foundations and hard standings leading to subsidence with foul waste water also entering sub-floors and cellars.

Repairing Defective Rest Bends

There are a couple of ways of repairing these bends when they fail and it really depends on the amount of movement that has occurred, if the bend is severely misaligned or it has dropped and rotated then excavation is probably the best solution, the problem here is that many modern properties have internal soil vent pipes and rest bends so it can mean major upheaval.

If the problem is due to leaking joints, hairline fractures or root ingress then we can reline the bends using Cipp liners or a patch repair system. Click here to see animation of Rest Bend Relining Process

related pages - drain patch repairs
  drainage junctions
  drainage gullies
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