Plumbing Tips – Inspection

It is clearly important to be able to gain access to all parts of the underground drains. This is usually done by providing inspection chambers at various points. To meet the Building Regulations, chambers have to be provided: at junctions between drains; where the drain changes direction or gradient; at or near the beginning of the drain; and at intervals of not more than 45m on long, straight runs. In between the inspection chambers, the drains should be laid in straight lines.
The usual form of an inspection chamber has sides made of brick, often cement-rendered either on the inside or the outside. At the base of the hole are open channels to which the drains are connected and along which the water in the drains runs.
The inspection chamber is at a junction between three drains. The branch drain is connected to the main one with a specially shaped half-channel bend which is swept in the direction of the flow of water through the main channel.
The channels are built up with benching – smoothly finished concrete shaped to direct any splashes back into the channels. The top of an inspection chamber is covered with a manhole cover a heavy, cast-iron plate set in a cast-iron frame. If there is a manhole cover within a building it usually has to be screwed down to the frame and the joint sealed with grease.
With modern drain materials, it may not be necessary to have full-scale inspection chambers at all junctions and bends in the drain. Instead, rodding points may be used. Small circular inspection chambers may also be fitted.
A rodding point has a length of pipe with a gentle bend connected at an angle to the drain. The other end of the pipe leads to ground level and is covered with a suitable removable cover. If the drain needs Introduction To Plumbing unblocking, the cover is removed and drain rods passed down into the drain. Rodding points are small and neat – unlike large, ugly manhole covers – but some inspection chambers may still be needed.
In older properties, the inspection chamber at the boundary of the property may have an interceptor trap fitted at the outlet of the channel. To gain access to the length of drain between the trap and the main sewer, the trap has its own rodding arm which bypasses the U-bend. The rodding arm is fitted with a stopper (sometimes secured with a chain) to prevent the drain water from bypassing the U-bend, too.
This inspection chamber may also be ventilated by means of a short pipe projecting above ground from the side of the chamber. The pipe is usually fitted with a grilled ventilator, behind which is a flap. The theory is that the flap allows fresh air into the drain but prevents foul air Plumbing Issues Cost from escaping. Ventilators are probably more of a hindrance than a help, and damaged ones can be removed completely rather than repaired. Interceptor traps also give problems the rodding arm stopper can fall out and cause a blockage in the trap if it is not suspended by a chain.

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