7.1 Common blockage materialsToilets and toilet pipes get blocked when people put the wrong things down the toilet. Some of the things which should never be put down the toilet are foodscraps, paper, rags, cans, bottles, grease and fat.
Wastewater pipes from sinks, basins and laundry tubs can get blocked if people put food waste, especially tea leaves, hot fat and other rubbish down them. If hot fat is poured down an outlet pipe, it will set in the pipe when it cools and cause a blockage.
In addition to blockages caused by these materials, main sewer pipes can get blocked in other ways, for example, tree roots growing into the pipe joints and soil blocking the pipe when it is broken by vehicle traffic.
7.2 Plumbing rodsPlumbing rods are pieces of equipment used to remove most blockages from sewer pipes. However, when sewer pipes are broken plumbing rods are not effective and the damaged pipe must be replaced.
The rods screw together so that they can be made as long as needed. They have different kinds of endings to help remove the blocking objects.
Fig 2.26: Plumbing rods.
To unblock the sewer pipe it is important to find an inspection opening (IO) below the blockage and push the rods up the pipe to the blockage.
Always remember which way the rods and endings have been screwed together and always twist the rods in the same direction.
If this is not done, the rods are likely to become unscrewed and be left in the sewer pipe. This will create a worse problem because the rods will also block the pipe. If this happens it will probably be necessary to dig up the sewer pipe and break it to unblock the pipe and get the rods back. This would have to be done by a licensed plumber.
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7.3 Unblocking sewer pipesThe larger sewer pipes have manholes set in them allowing access to the pipe. They are often about a metre underground and are large boxes which usually have walls made of concrete. The pipe opens into the box on one side and starts again on another side.
The lids, which are made of metal, can be lifted to allow someone to look down into the sewer to see if there is evidence of a blockage, for example, wastewater build-up in the manhole.
Fig. 2.27: A blockage in the sewer pipe can cause the wastewater to build-up in the manhole.
Extreme care must be taken when opening the lids of sewer pipes as poisonous and explosive gases can build up in these pipes.
Before attempting to unblock a sewer pipe it is important to remember:
- Before making an inspection, always wait several minutes to allow any poisonous or explosive gases to escape
- Never smoke while doing this work
- Never do this work alone
- Never enter a manhole without proper safety measures. It may be necessary to wear breathing equipment or to ventilate (add fresh air) to the manhole and sewer pipe. The gases in it can kill.
If there are no manholes, then there will be IOs with cement or plastic caps on the pipes. There may be a concrete box around the inspection opening. Sometimes these are below the ground and are not easy to find. It may be necessary to dig to find them.
It is a good idea to get the sewer pipe plans for your community so that you can refer to the plans before starting to dig.
Fig. 2.28: Unblocking a sewer pipe.
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7.4 Unblocking fixturesFor the plumbing system to work, the pipes must be free of blockages. If the pipes are blocked, the toilet, shower, laundry tubs and/or the kitchen sink will not carry the wastewater away properly.
If a fixture is blocked, the wastewater may flow onto the floor of the house. If the sewer pipe is blocked, the wastewater may flow from the DT onto the ground outside. Contact with this wastewater may cause disease.
To unblock a sink, shower recess or any tubs, first remove any larger pieces of rubbish and then try using a plunger or a mop to finish unblocking the pipe. Pipes from sinks, basins and tubs and the small waste pipes leading to the larger sewage pipes outside the building will have small IOs.
These may be sealed with a screw plug, either close to the fixture or on a bend. The plugs on these IOs can be removed to allow access to blockages.
A plunger consists of a heavy rubber cup which is attached to a handle on the closed side. It is used by placing it over the opening to the blocked outlet pipe and then thrusting it up and down quickly over the hole. The suction caused by this action will help to move the blockage.
A mop can be used to unblock a pipe in the same way. It is best to use a mop to unblock a toilet pan.
If using a plunger or a mop does not work, the pipes will need to be examined through IOs or a manhole to find the blockage. This can then be removed with plumbing rods. If these are not available, a hose may work.
Fig 2.29: Unblocking fixtures.