On looking after sump tanks

April 5, 2012

The sump in question



Almost every house and apartment in urban India would have to have a sump tank to store water, a sump being an underground storage tank. Since water from city lines would be infrequent in supply, sometimes once in four to five days, stocking up is the only way to have access to it 24/7. The pressure at which water is delivered by city utilities is also generally abysmal. This means water will not rise to any level but an underground sump tank to be subsequently pumped into over head tanks for gravity based distribution. When water runs short sumps become the place to receive water from public or private water tankers.

Here is a list of things one needs to do to ensure that sumps work well.

Check for leaks: Sumps can leak copious amounts of water without us being aware about it. Fill up the sump tank to a level. Mark the level and observe overnight. If the water level has fallen by even as much as a centimeter it means the sump is leaking. Call in a professional service to repair the leak which is also done with a coat of leak-proof paint nowadays. Repairing a leaking sump will save you and the city thousands of litres of water annually.

Observe for silt: Too much silt may sometimes come in from the water source. By itself silt may not be harmful but it can choke up water lines especially damaging to washing machines, dish washers and solar water heaters. Removing the silt periodically and placing a floating intake outlet to the overhead tank can help.

Algae and moss: The rapid growth of algae and moss can indicate nutrient rich water and can also spoil the water as well as choke water lines. Cleaning the sump, scraping the algae and using bleaching powder to clean it once again should control this issue.

The float valve: A malfunctioning float valve from the inlet pipe can cause the sump tank to overflow and waste water. Check and repair the float valve periodically.

Outlet to sump: Sometimes an overflow outlet is given to sump tanks especially if it also used for rainwater harvesting. Ensure that the outlet is not blocked and cover with a mesh on either side to prevent lizards and cockroaches from entering.

Sump cover: These tend to be the weak points of sump tanks allowing dirt and dust to enter and sometimes rust too. The hinges need to be periodically oiled and painted with a rust proof paint and rubber sealed if possible.

Pumps: The inlet valve of pumps may choke or be blocked by dirt and silt; these need regular cleaning to ensure the efficiency of the pumps and not to overload the motors.

Residual chlorine: The city utility ensures quality of water through residual chlorine of 0.2 mg/l at the sump level. This ensures that all bacteria are destroyed and the water is not harmful. Using a small chlorine testing kit periodically check whether the residual chlorine is of the requisite level, if not take it up with the authorities.


The overall storage of water created in cities like Bangalore through individual sump tanks built using ordinary brick or concrete blocks runs into millions of litres capacity. It is only fair that the city utility and individual owners look after this asset and ensure that it is in prime condition without leaking or jeopardizing water quality. After all the responsibility of the city water utility ends where the individual sump tank begins.


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