How To Clean Your Concrete Water Tank In 6 Easy Steps

Concrete is an excellent material for water tanks since it allows for custom-sized tanks and keeps water cool year-round, whereas metal and plastic tanks can overheat in the summer sun. However, when it comes to concrete water tanks, such as cisterns and wells, it’s critical to remember that concrete is porous, whereas metal and plastic are not. This means that concrete can serve as a breeding ground for algae, E. coli, and other microorganisms, making routine cleaning and disinfection necessary.

Steps On Cleaning Your Concrete Water Tank

Below are six steps to take when cleaning your concrete water tank.

Cut the water supply off and drain it.

Close any exterior water supply valves. If it’s a rainwater collection system, you’re set. Now you must drain the tank to clean it. The water supply looks infinite, but shortages rise in severity and regularity that is why sometimes, you would need to call in companies like Bright Water Services Inc. Watering the grass, washing cars, and other gray-water-safe activities are allowed even if it isn’t safe to drink.


If preserving water isn’t possible, drain it away from structures to avoid oversaturating the ground and flooding basements or other areas.

Decontaminate the catchment area.

If your system has a catchment cistern or tank, clean the exterior first. Scrub the tank outside with a 5-gallon pail of soapy water and 12 cups of bleach. Rinse well.

Get inside. 

Open the tank access hatch. Some tools are needed. If cleaning the tank necessitates going inside, authorities advise confined space certification since trapped gasses or low oxygen levels may exist.


If you must enter the tank, always have a companion on duty in case of emergency. Using a flashlight, search for sediment. Clear it.


Fill a 10-gallon bucket halfway with water and add 1 cup of unscented household liquid bleach ranging in strength from 5% to 8.25 percent. Scrub the inside of the tank thoroughly with a firm brush. Rinse thoroughly with clean water.

Cleaning the tank.

Even if you’re using bleach and water again, scrape the surface to remove any sediment and biofilms before disinfecting.


After cleaning your tank, the CDC recommends refilling it with drinkable water. They recommend three cups of home liquid bleach for disinfection with 5 percent to 8.25 percent strength per 100 gallons of water. So 15 cups of bleach for a 500-gallon tank. Let the water-bleach mixture settle for 12 hours.

From draining to drinking.

After soaking for at least twelve hours, drain the tank fully. Because bleach can harm your grass or garden, dispose of it in storm drains. Then run your faucets until there is no more bleach aroma before water tank filling. However, other health boards recommend refilling and draining concrete tanks several times to eliminate the bleach because concrete is porous and can hold it.


When adding potable water to the tank, use one tablespoon of bleach every 100 gallons to help prevent microbial development.


Experts advise cleaning the concrete water tank every year, if not every two years. Testing the water is also advised. Don’t assume that water that “looks” clean is clean if it tastes bad or causes gastrointestinal pain. Water testing labs can detect microbial problems in three days or less by analyzing your water sample. If it’s not safe, empty it for greywater use and continue the process until it is.