Blocked Drains – Problem Solving
Lifting manhole covers to access blocked drains
♦ Gently tap all the way around the edge with a heavy hammer or lump of wood.
♦ Apply heat from a blowtorch around the edges to release the seal.
♦ Apply penetrating oil to the edges and leave to work for several hours.
♦ Use an old garden spade as a lever to lift the cover.
♦ Thread ropes through the cross bars and around a stout length of timber, then lift with the aid of a helper (but check first that the bars haven’t rusted through).
When replacing a cover, apply motor grease around the seal to prevent future jamming.
Hidden manhole covers
When you have blocked drains and it is necessary to remove the manhole covers, you can sometimes encounter other problems – with the manholes themselves. Manholes or smaller clearing eyes are supposed to be included wherever a drain branches or changes direction. Very few drains are laid without them, so if you can’t find any covers the chances are they have been hidden — usually by garden outbuildings or loose-laid paving.
Larger and older properties may also have a manhole inside — often in the hallway. This should be the double-sealed type, with a-down cover.
The positions of hidden manholes can usually be fixed by taking the soil stack, gully and road as reference points: drains always run in straight lines between ‘features’ and you know that they must eventually converge towards a public sewer in the road. Bear in mind, though, that you may share a manhole with your neighbour — or even with several neighbours if you live on an estate served by a private sewer.
Another trick is to check where the manholes are in neighbouring properties — if the houses are identically built, you can assume that your own manholes are in the same place. And as a last resort, you could hire a metal detector to track down the covers.
An old fashioned method of providing a seal between the household drains and the public sewer was to place a U-shaped trap after the last manhole in the run. Known as interceptors, these are a common place for blockages in the drains to occur.
This should partially empty the manhole, allowing you to rod through both the bypass pipe and the main outlet. If this doesn’t work, there are two possible causes of the problem.
♦ The blockage is further down the run, possibly near the public sewer. In this case call in your local water undertaking, since the problem is likely to involve other properties connected to the same system.
♦ The chain holding the stopper has rusted through, allowing the stopper to fall into the interceptor trap. In this case you should seek professional advice.