LAST UPDATED: 9th January 2023 by The Editorial Team
Summary: Step by step guide and video showing how to maintain a drain system, unblock a drain, and unblock an interceptor chamber.
Unblocking a drain
The house owner is responsible for maintaining the drainage system up to where it joins the sewer, except in houses built before 1937, in which case the local council must maintain the system, often recuperating the funds from householders.
Drain pipes run in straight lines, with inspection chambers at each pipe joint or gradient shift; an inspection chamber is covered by manhole cover. The most common system connects all waste water pipes and soil pipes at a single stack. However, in pre-war houses, you may find two separate pipe systems.
If sewage overflows from an inspection chamber or gully, or you can smell sewage, you will need to unblock a section of drain. You can hire drain rods and a variety of heads from most hire stores. If the smell persists or you notice any leaks, contact your local council.
- Remove the manhole cover covering the inspection chamber nearest the house. Some manhole covers have keys to help with removal. Otherwise lever them up with a spade. Manhole covers can be heavy so get somebody to help you move them aside. If the cover is rusty, use a screwdriver or hammer to loosen the rust and soak any bolts in oil.
- If the chamber is empty, the blockage is between the inspection chamber and the house. If it is full, move on to the next chamber in the drain run.
- Continue checking the chambers until you find one that is empty. If you cannot find one, and the last chamber before the main drain, cesspool or septic tank is full, then either the blockage is between the chamber and the main drain or your septic tank needs emptying. See below for clearing a blockage in an interceptor chamber.
- When you have located the blocked pipe section, wearing a pair of long, heavy-duty rubber gloves, insert a flexible drain rod fitted with a plunger head into the pipe in the direction of the suspected blockage.
- Connect more rods together to feed the rods along the pipe, turning the rods clockwise.
- When you locate the blockage, probe it with the plunger. If it does not shift, exchange the plunger head for a corkscrew head.
- Flush out the drain with a hose or by filling the bath and sink with water and pulling the plugs out at the same time.
- Clean the rods and gloves with diluted disinfectant.
Unblocking an interceptor chamber
Older houses often have an interceptor chamber before the main drain. If this is full, the blockage is usually located in the U-trap at the end of the open channel under the manhole cover.
- Just above the trap is a section of pipe with a plug in it, which you should remove. Some stoppers are on a chain otherwise feel for the handle with a stick and try to hook it out of the way.
- Insert a flexible rod into the pipe opening and down into the trap.
- If the trap is still blocked, reach down into the chamber to remove debris from the trap with a trowel. Make sure you wear a respiratory mask and eye protection.
- Replace the stopper. Before replacing the manhole cover, smear grease around the frame to stop rust.
- Large screwdriver
- Garden spade
- Heavy-duty rubber gloves
- Drain rods
- Safety goggles
- Disposable face mask
- Oil and grease