OPEN CHANNEL MANHOLES
Brett Martin chamber bases can be used in the bottom of a constructed manhole arrangement. The chamber base is positioned carefully in concrete to give full support throughout its diameter. Benching is sloping upwards from the base to the manhole walls at a gradient of 1:12. All construction must be in accordance with BS8301:1985, Figure 10.

FIGURE 10



A large range of 1 /2 and 3 /4 channel fittings offer the contractor a wide choice of constructional methods.

Fittings are available in 110mm, 160mm and 200mm diameters. Channel fittings for larger bore pipe can be fabricated on request.

Two systems are available:

(i) Level invert system Figure 11
(ii) Stepped invert system Figure 12

A level invert system is advantageous when invert levels need to be accurate. The range consists of junctions, bends, tapers which have to be solvent welded into position. No solvent welding is required on a stepped invert system.


FIGURE 11
LEVEL INVERT SYSTEM

FIGURE 12
STEPPED INVERT SYSTEM

Solvent welding must be carried out in the following way to ensure a sound and lasting joint:

(i) All spigot ends must be square and chamfered
(ii) Both surfaces should be free from dirt and water
(iii) With a clean brush apply Brett Martin solvent cleaner to both surfaces and allow to dry
(iv) Again with a clean brush apply an even coat of Brett Martin solvent cement
(v) Immediately insert the coated spigot into the socket and hold in place for about a minute

N.B. A narrow cut-off pipe may be sprung into the joint to hold the assembly in position. See Figure 13, but it must be removed when the joint is set.

FIGURE 13
SOLVENT WELDING



The full range of Brett Martin Channel Fittings are supplied with a keyed surface, to ensure excellent adhesion to the concrete benching.

FIGURE 14
ILLUSTRATES ALTERNATIVE ASSEMBLIES



Many additional combinations are possible using the above and other Open Channel Fittings.

BACKDROP MANHOLE
CONSTRUCTION
A backdrop installation is required when two or more pipes, at different invert levels, are to meet at one manhole. Minimum trench excavation is therefore needed to join the pipework together. The vertical section of a backdrop can be constructed internally or externally.

FIGURE 15
INTERNAL BACKDROP



INTERNAL CONSTRUCTION
To construct an internal backdrop as illustrated in Figure 15 use:
1 No 5091 - Screw Access Cover
1 No 4081 - Triple Socket Branch 87 1/2 °
1 No 5041 - Single Socket Bend 87 1/2 °
section of pipe for vertical drop The vertical section should be securely fixed to the manhole wall using Pipe/Socket Fixing Brackets (BS407) from the Brett Martin Soil Range, and held with stainless steel screws.


FIGURE 16
EXTERNAL BACKDROP

EXTERNAL INSTALLATION
The vertical section of the installation is this time outside the chamber wall. The fittings required to construct an external backdrop are as shown in
Figure 16:
1 No 5091 - Screw Access Cover
1 No 4081 - Triple Socket Branch 87 1/2 °
1 No 5001 - Pipe Coupler
1 No 4031 - Double Socket Bend 87 1/2 °
plus a suitable section of vertical pipe Note: 160mm installations may be constructed using similar 160mm fittings.

RODDING ACCESS
When installed correctly, the use of rodding points can eliminate the need for expensive Inspection Chambers and Manholes, significantly reducing the cost of installation.

HEAD OF DRAIN RODDING POINT A Rodding Point as shown in Figures 17 and 18 can be used at the head of a drain in place of an inspection chamber or manhole. The rodding eye itself is made from cast alloy and has a 110mm spigot allowing easy connection to the system. Being set at 45° it allows easy rodding of the system.

FIGURE 17
HEAD OF DRAIN RODDING POINT



NB Sealed square and socketed version of the aluminium rodding point is also available code 5592.



Shows how Rodding Points can minimise the number of inspection chambers and manholes on a typical surface water application.


UNIVERSAL RODDABLE BOTTLE GULLY
The Brett Martin Universal Roddable Bottle Gully (as shown in Figure 19), may be used with a wide range of grids and sealing plates. It may be rotated leaving the grid square to the wall thus giving a more direct line of drainage resulting in economy of fittings.
A full 100mm diameter access, gained by the removal of a simple rubber cap, enables a wide range of cleaning equipment to be used.
The unit can be used instead of a traditional gully assembly and in certain applications, can remove the need for an inspection chamber, Figure 19.

FIGURE 19
RODDABLE BOTTLE GULLY
INSTALLATION DETAILS


FIGURE 20
HOW A RODDABLE BOTTLE GULLY CAN ELIMINATE THE USE OF INSPECTION CHAMBER OR MANHOLES