Drainage System Maintenance

So there you are feeling justifiably relaxed, having purchased the ideal home, when you hear a dripping sound. Undoubtedly having dealt with this minor problem you will merrily discuss how fortunate you were to be at home when the dripping started, However, as most home owners are aware, disasters rarely happen to suit your programme. It is therefore wise to conclude that the minimum effort of regular maintenance can, as with cars (which we are more accustomed to maintain regularly), reduce the number of unexpected calamities. In this article we propose an ‘autumn maintenance programme’ to cover electrics, plumbing, heating and drainage, and timber, and a ‘five yearly maintenance programme’ to cover external decorations, roofing and external walls.

Drainage systems explained

I doubt if there are any two identical drainage systems in this country. There are numerous combinations from district to district, using different materials and different methods of moving the waste away. You may not even be on main drainage. You may be one of the fortunate few blessed with septic tanks, the maintenance of which will probably have been impressed on you by the previous owners. The system on the opposite page is probably the most common and is generally typical of new housing.

Underground drainage

Here we have a choice of two systems. One is where the rainwater is kept separate from the waste/soil water. The other is where both are combined underground at the manholes, and discharged to the main sewer in the street. I understand that in some areas you are not allowed to drain rainwater into the drainage system at all. It is intended that you form guttering systems on your own property.

A single-stack system

This is the modern form of drainage above ground where the WC, basin and bath are connected separately to one downpipe. To prevent suction breaking the traps, the wash-hand basins, baths, showers and WC are all within two metres of the downpipe.

A two-pipe system

This is the same as the above, but the WC is taken separately to the manhole.

A vented system

This applies to both the above systems when the fittings are farther than two metres away from the down pipe. Then, to prevent the traps being broken, a vent pipe is located close to each individual trap to let in air and prevent the suction building up.

Traps explained

The purpose of a trap is very simple: to prevent pong coming from the main sewer into your house, A trap is formed with a U bend of pipes, in which water is trapped; between 1%” and 3” for baths, wash-hand basins and showers, and approximately 6” deep for WCs, rainwater gullies and yard gullies. Suction is formed between the trap and the discharged water; the larger the distance the greater the suction, so to prevent the water in the trap being sucked out, basins, baths, showers and WCs are all within 2 metres of the downpipe in a single-stack system. There is one special trap which is intended to stop rats coming from the main sewer into your drainage system. This is the interceptor trap, and is located either at the edge of your property or in the last manhole before the main sewer. Too often when the drainage is blocked, the interceptor stopper is removed and this allows the rats to climb straight in without attempting to go through the trap. So in your maintenance, look for the stopper and tie a piece of polypropylene rope to it. Attach this to a hook at the top of the manhole and then you will be able to pull it and release a blockage.