How To Clean A Concrete Water Tank With Ease In 6 Simple Steps

Concrete makes an ideal water tank material because it allows for custom-sized tanks and keeps water cool year-round, whereas metal and plastic tanks can overheat in the summer sun. However, it’s crucial to remember that concrete water tanks, such as cisterns and wells, are porous, whereas metal and plastic are not. Thus, concrete can act as a breeding ground for algae, E. coli, and other bacteria, necessitating constant cleaning and disinfection.

Steps On Cleaning Your Concrete Water Tank

The following are six steps to cleaning a concrete water tank.

Cut the water supply off and drain it.

Any exterior water supply valves should be shut off. If the system is a rainwater collection system, you’re good to go. Now you must drain and clean the tank. While the water supply appears limitless, shortages are becoming more severe and frequent that is why water delivery services are becoming more popular and a good example is this website. Even if the water is not safe to drink, watering the grass, washing automobiles, and other gray-water-safe activities are permitted.

If it is impossible to conserve water, divert it away from structures to avoid oversaturating the earth and flooding basements or other locations.

Decontaminate the catchment area.

If your system incorporates a catchment cistern or tank, begin by cleaning the exterior. Using a 5-gallon pail of soapy water and 12 cups of bleach, scrub the tank outside. Thoroughly rinse.

Get inside. 

Open the access hatch to the tank. A few tools are required. If cleaning the tank requires going inside, authorities recommend obtaining restricted space certification due to the possibility of trapped gasses or low oxygen levels. If you are required to enter the tank, always have a partner on duty in an emergency. Utilize a flashlight to search for and clean sediments.


Half-fill a 10-gallon bucket with water and add 1 cup of unscented household liquid bleach with a concentration ranging from 5% to 8.25 percent. With a stiff brush, scrub the inside of the water supply reservoir completely. Thoroughly rinse the area with clean water.

Cleaning the tank.

Even if you are disinfecting with bleach and water, scrape the surface to remove any sediment or biofilms before disinfecting. The CDC suggests that you replenish it with drinkable water after cleaning your tank. They propose three cups of household liquid bleach with a concentration of between 5% and 8.25 percent per 100 gallons of water for disinfection. Thus, 15 cups of bleach are required to clean a 500-gallon tank. Allow 12 hours for the water-bleach solution to settle.

From draining to drinking.

Drain the tank completely after at least twelve hours of soaking. Because bleach can be harmful to grass and gardens, it should be disposed of in storm drains. Then, run your faucets until the bleach odor is gone. On the other hand, other health boards propose repeatedly refilling and draining concrete tanks to eliminate the bleach, as concrete is porous and can contain it.


When adding potable water to the tank, use one tablespoon of bleach for every 100 gallons to aid in microbial growth prevention.


Experts recommend cleaning the concrete water tank annually, if not twice a year. Additionally, testing the water is recommended. Never assume that water that “appearances” to be clean is clean if it tastes terrible or causes stomach discomfort. Water testing labs can uncover microbiological concerns in three days or less by examining your water sample. If deemed unsafe, drain it for greywater use and repeat the process until it is deemed safe.