300 Gallon Water Storage Tank: How to Clean, Prepare, and Fill?

300-gallon water storage tanks are ideal water containers that help one thrive in emergencies. During water scarcity, these enormous water tanks ensure a family gets an adequate water supply. That said, storing water for emergencies does not mean filling the tank up, closing the lid, and not reopening it until a problem strikes.   For the best water solutions, visit USA Berkey Filters.

Though water does not come with an expiration date, it can contaminate when stored in unhygienic conditions — soon enough, it will become a breeding ground for disease-causing bacteria and algae, making it unsafe for use. To avoid this, periodic maintenance is a must.

Continue reading this detailed guide to clean your 300-gallon water storage tank and store water safely.

Preparing water tanks for storing water

As per the World Health Organization (WHO), it is essential to clean and disinfect water tanks for safer water storage. Only treated water tanks with lockable lids are ideal for storing large quantities of water. Here are the proper steps to make a water tank suitable for water storage.

Dispose of liquid

Before you clean your 300-gallon water storage tank, discard the water previously stored. To avoid localized flooding and soil erosion, dispose of the water to a sewer network — ensure the water follows a channel to its disposal point. Additionally, prevent disposing of in the nearby water bodies, as it will disturb the aquatic ecosystem — the high chlorine levels in water can kill fishes and plants.

Clean the internal surface

After draining the leftover water properly, scrub the inner walls of your 300-gallon water storage tank with hot water and a mild detergent — household laundry soap will also do the job. With the detergent and water mixture, clean the tank using a stiff brush or a high-pressure jet. For extended reach, attach a long pole to the scrubbing brush. Remember to clean the corners religiously, too.

With water, rinse the tank; you can even use a high-pressure hose pipe. If these pieces of equipment are not at your disposal, simply fill the tank with hot water and wait for a few hours before draining.

Do not forget to clean the hoses, pipes, and pumps used for filling and emptying the tank. To clean, rinse them with the same mixture of water and detergent you used to clean the tank. Follow by rinsing with clean water.

Disinfect the tank

Only cleaning will not ensure safer water storage environments inside the tank; disinfecting it is a must too. Chlorination is the most effective and economical way to disinfect a tank, and High-strength calcium hypochlorite (HSCH) is considered the best disinfecting agent for purifying water.

The volume of the water tank determines the quantity of chlorine to add. Ideally, you should add about 80 grams of granular HSCH for every 1000 liters of water in your 300-gallon water storage tank. After filling the tank with water, close the lid and leave it to stand for 24 hours.

After a day, empty the tank by draining out all the water. Follow by adding normal water once again and flush after 30 minutes. Once done, your water tank is fully ready to be filled with clean water.


Vigilance is key when it comes to safe water storage. Keep going back to your water storage tank, and inspect it for leaks and algae formation and repair all damages. It will ensure you only get a supply of healthy water that is free from all harmful bacteria.