How do I descale my water tank?

Lots of people think that tank water is drinkable – after all, what could be purer than rainwater from the sky?

Table of Contents Show

Step 1 – Wait until after summer as water will be lowest.
Step 2 – Drain your tank
Step 3 – Remove the sludge
Step 4 – Connect power and fill the tank again
Consider using UV filters for drinking water
Things You'll Need
References
About This Article
Reader Success Stories
Did this article help you?
How do you remove calcium from a water tank?
Can I use vinegar to descale my water heater?
Which chemical is best for water tank cleaning?

The truth is that while rainwater itself is free of chemicals and other additives that can be found in our drinking water, you do need to clean your rainwater tank regularly to ensure high-quality water.

Tank water can gather a variety of impurities both on its way down from the clouds and within your rainwater tank. For example, smog and smoke haze particles can attach to droplets of water as they fall through the sky. Within your rainwater tank, bacteria, leaves and other debris may contaminate your water.

Mosquitos may try to breed within your tank water too – potentially causing your tank to become a haven for disease.

The good news is that if you take the time to clean your tank each year, you can prolong its life and keep your water clean and healthy. It’s relatively simple to clean your rainwater tank, and maintain clean water throughout the year.

Step 1 – Wait until after summer as water will be lowest.

It’s recommended that you wait until the end of summer to clean your rainwater tank. That’s because the water level will be at its lowest at that time.

First, turn the power off if you have an electric pump, and pull the plug completely out of its socket to be sure there is no electricity flow remaining.

Step 2 – Drain your tank

Now it’s time to drain your tank. Use the remaining water around your garden, top up your pool, or fill your pond. Then run some fresh water from your garden hose through the tank inlet to flush out any remaining dirty water. Keep doing this until the water runs clear – you may need to increase water pressure to give the outlet a really good rinse.

Step 3 – Remove the sludge

Here comes the ‘fun’ part… removing sludge. Rotting leaves and other organic debris can make the bottom of your tank pretty slimy.

It’s important to note that working inside a tank can be dangerous, so consider using a professional tank cleaner if you can.

To stop sludge building up in the first place, you may want to use a first flush diverter (or roof washer) which diverts the flow of water away from your catchment system, or leaf strainers which stop organic matter from entering your tank.

If you’re already using these, don’t forget to clean them out as well – if they’re clogged they can’t do their job.

Step 4 – Connect power and fill the tank again

Now you have a clean tank, you can reconnect your power and set up your tank again. Fill the tank to cover the pump opening, and flush the taps in your property to bring through clean water from the tank.

It’s a good idea at this stage to clean your gutters as well – the cleaner your roof, the less likely your tank will fill with debris and insects that rainwater washes down into the tank. Ensure that your strainer screens are still in good enough condition to prevent insects, leafy debris and dead animals from falling into your tank.

You should be cleaning your strainers around 3 times a year. Also it’s wise to check them after big storms and other significant environmental events (such as a dust storm or bushfire) to make sure they haven’t been damaged, and are unclogged.

Consider using UV filters for drinking water

If you use your rainwater tank to supply drinking water, you may want to consider using UV air and water filters to kill pathogens and help maintain a clean water supply. Used along with carbon filters, UV water filtration systems are the best line of defence against bacteria and viruses.

UV energy destroys microorganisms that may cause illness by attacking them at their genetic core and eliminating their ability to reproduce.

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ASC Water Tanks have been supplying Australian homes with rainwater tanks since 2007. We sell top-grade Australian Made water tanks to support our economy and to deliver a superior product to our customers.

To discuss how to set up a rainwater harvesting system in your home, contact us here or give us a call on 1300 229 606.

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Cleaning your water tank can be a daunting task, but it is important to ensure the water inside stays clean and bacteria-free. You should clean your water tank at least once a year. Water tanks will acquire algae, silt, and bacteria over time, all of which can be harmful if not taken care of.[1] When you clean your tank, you should follow proper processes for draining it, cleaning the interior walls, and disinfecting the tank. By following these methods, you can be confident that your water is as clean and safe as possible.

1
Open the outlet valve or tap. The first step to cleaning your tank is to empty all of the water from it. To do so, open the outlet valve or tap at the bottom of your tank and let all of the water flow out.
- Connect a hose to the open valve in order to direct the water to a location where it will not cause any localized flooding or erosion.
- Permanent water tanks have a washout valve that is located at the base of the tank. If your water tank is permanent and contains a washout valve, use this to drain the tank instead of the regular outlet valve or tap.[2]
2
Scoop water in the bottom of the tank out with a bucket. Since the outlet valve or tap is usually located above the bottom of the tank, you may need to remove some remaining water from the tank after draining it. To do so, use a bucket to scoop as much water out as possible. Once the water in the bottom is too shallow to scoop with a bucket, use a plastic cup or coffee mug to continue scooping it out.
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3
Remove any remaining water. You probably won't be able to get all of the water out by scooping it up with a bucket or cup. Remove the remaining water using one of the following methods:
- Use a wet/dry vacuum to suck up any water that remains.
- If you have a small tank and can safely tip it up, you can do this to drain any remaining water from the tank.
- Once you've got all but a very small amount of water out of the tank, you can use towels to soak up any water that remains.[3]

1
Make a cleaning mixture. While you may be able to remove a lot of the sediment and residue from your tank without using a cleaning mixture, using one can help make this job easier. Simply mix hot water with laundry detergent powder or liquid to make a cleaning solution.[4]
2
Scrub the inside of the tank. Use a bristle brush or abrasive sponge to scrub the inside of the tank, with or without your cleaning solution. Move your arm horizontally from side to side while applying a good amount of pressure on the brush or sponge. Continue doing this around the entire inside of the tank, until you remove as much slime and sludge as possible.
- You may need to use a brush with a long handle, depending on the size of your tank. This type of brush may be more difficult to maneuver, but will allow you to reach the bottom of the tank safely. If you're using a long-handled brush, you'll probably need to move the brush up and down vertically instead of horizontally.[5]
- Avoid brushes with steel bristles or sponges made of steel. Plastic can scratch easily and these materials will probably be too harsh for a plastic tank.
3
Use a power washer. You can also use a power washer to clean the inside of your water tank. You can use the power washer by itself or in conjunction with scrubbing the inside of the tank, depending how tough the sediment and residue is to remove.[6] Pressure washers come in a variety of sizes and strengths, but one with a pressure range between 1,300 and 2,400 psi works best for most household tasks. Follow these steps to clean the inside of your tank with a power washer:
- Fill your power washer with water or cleaning solution.
- Start by holding it about four feet away from the surface you're cleaning. Move closer until you find the distance that works best for removing dirt, sediment, and debris.
- Hold the pressure washer so the water hits the interior wall of the tank at a 45 degree angle.
- Continue this until you are satisfied that you've removed all the dirt and sludge from the walls of your tank.
- Pressure washers are very powerful, so always wear safety goggles when you're using them, never point them at another person or animal, and follow all other safety regulations. It is also a good idea to have someone with knowledge of power washers give you a lesson on starting and using them before using yours.[7]
4
Use baking soda on particularly dirty walls. If you're having trouble getting all of the sediment and dirt off the interior walls of your tank, try sprinkling the walls with baking soda and scrubbing them with your brush or sponge.[8]
5
Scrub corners and joints. While you are scrubbing, pay special attention to corners and joints in your tank. Residue stuck in these areas can be difficult to clean, so you may need to spend a little extra time getting into these areas. Try using a small toothbrush to help you reach and scrub these difficult places.[9]
6
Rinse thoroughly. Once you're satisfied that you've scrubbed most or all of the residue from the inside of your tank, you need to rinse it very thoroughly. This is best done by using a hose to spray down the interior walls, making sure to get into all the nooks and corners. You can also use a pressure washer filled with clean water to do this.
- Alternatively, you can rinse the tank by filling it with hot water and letting it stand for several hours. Drain the tank, making sure you collect and safely dispose of the drained water. Repeat this process until the water is completely free of detergent and sediment.[10]
7
Remove remaining liquid and residue with a vacuum. Some water tanks may not allow you to drain all of the liquid from them. For example, if your tank is too large to tip on its side and spray out, you probably won't be able to spray all of the detergent and residue out of the tank. In order to remove this residue, you can vacuum it out with the hose attachment of a wet/dry vacuum. Make sure you get the hose into the cracks, crevices, and corners of your tank in order to remove all of the residue.
- After vacuuming, you may need to take a clean rag or mop head and run it along the bottom of your tank to clean any areas that still have sediment on them.
8
Flush your tank's hoses and pipes. Pour some of your cleaning solution into these pipes and hoses. Then, use your water pump to pump the solution through the pipes, removing any sediment and dirt inside them. Complete the same process with hot water until the pipes and hoses are free of detergent.[11]

1
Fill your tank three quarters full with clean water. Once you've scrubbed out the inside of your tank, you can then perform the process of disinfecting it. To start, use a hose to fill your tank three quarters of the way full with clean water.[12]
2
Add chlorine bleach to the tank. Next, add chlorine bleach to the tank in the ratio of 50 ppm (parts per million) to the amount of water. Follow these guidelines to determine how much household chlorine bleach (5% bleach) to use in your tank:
- For a 250 gallon tank, use 4 cups of bleach.
- For a 500 gallon tank, use ½ gallon of bleach.
- For a 750 gallon tank, use ¾ gallon of bleach.
- For a 1,000 gallon tank, use 1 gallon of bleach.
3
Fill the rest of the tank with water. After adding the appropriate amount of bleach, fill the tank to volume with clean water. This will allow the bleach to mix with the rest of the water in the tank.
4
Leave the mixture in the tank for 24 hours. Once you have the tank filled with chlorine and water, leave this solution sit inside the tank for 24 hours. Be sure no one comes in contact with the solution during this time because it can be harmful to people and animals.
5
Check the amount of chlorine in your solution periodically. During the 24 hour period that you are letting the solution sit inside your tank, use chlorine strips to periodically check the solution to see the amount of chlorine. You want to maintain a measurable chlorine reading throughout the entire 24 hour process. To check this, dip one end of the chlorine strip in the solution and follow the instructions on the packaging to determine how much chlorine is present. If there is no detectable amount of chlorine, repeat steps two through four.
6
Drain the tank completely. Using a hose, drain all of the solution out of your water tank. Hook the hose up to the valve on the bottom of your tank and allow all of the solution to flow out toward your sewage system. Make sure you point the hose away from any vegetation, lakes, and any other areas that may be damaged by the chlorine bleach in the mixture. Do not drain the tank directly into your water distribution system either.
- Remove any remaining liquid by scooping it out with a bucket and then using towels, a clean mop head, or a wet/dry vacuum to pick up the rest.

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Question
how to stop leak or repair plastic water tank

The easiest method to repairing a leak in a plastic water tank is to purchase a plastic tank repair kit. These kits come with all the materials needed to fix your tank and instructions on how to use them. If this doesn't work, you can try melting a spare piece of plastic over the hole in your tank using a heat gun and a putty knife to smooth the plastic over the hole. If these fixes don't work, you may need to call a professional to fix your tank.

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Wear rubber gloves to protect your hands and safety goggles to protect your eyes while cleaning the tank.
As a small thank you, we’d like to offer you a $30 gift card (valid at GoNift.com). Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy!

Thanks for submitting a tip for review!

Getting into your water tank to clean it can be dangerous, so if you have to do this, use caution.
As a small thank you, we’d like to offer you a $30 gift card (valid at GoNift.com). Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy!
Be careful about where you drain the liquids from inside your tank. Letting too much water out at one time can cause erosion or flooding. Allowing liquid that contains detergents and bleach flow into places with vegetation or into bodies of water can also be harmful.
As a small thank you, we’d like to offer you a $30 gift card (valid at GoNift.com). Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy!

Things You'll Need

Hose
Bucket
Plastic cup or coffee mug
Wet/dry vacuum
Towels
Mop heads
Laundry detergent powder
Bristle brush or abrasive sponge
Long-handled scrub brush (optional)
Power washer (optional)
Baking soda (optional)
Toothbrush (optional)
Household bleach
Chlorine testing strips
Rubber gloves
Safety goggles

References

About This Article

Article SummaryX

To clean a plastic water tank, open the outlet valve or tap and let the water flow out. Next, mix hot water with laundry detergent and use a bristle brush to scrub the inside of the tank with the cleaning solution to remove slime and sludge. Then, rinse out the tank thoroughly and flush the hoses and pipes. Finally, fill your tank with a mixture of clean water and bleach and let it sit for 24 hours to disinfect it. For tips on using a pressure washer to clean out your tank, read on!

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Reader Success Stories

Madalaine Mason
Apr 8, 2018
"We have just bought a second motor home, and we found that the water tasted nasty; the tanks need cleaning out. I..." more

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How do you remove calcium from a water tank?

Treat with organic chemicals. — The most effective chemicals for combating calcium buildup are vinegar or lye. Once you flush your water heater, let the chemicals sit in the tank for a few hours, then flush it again before turning the heater back on for use. Keep it at the right temperature.

Can I use vinegar to descale my water heater?

Let vinegar set in water heater for a period of at least six (6) hours. 7. After the allowed time has passed, reconnect inlet, outlet, or T & P valve open drain valve and turn on the water to flush out the dissolved sediment and vinegar.

Which chemical is best for water tank cleaning?

Chlorine is most commonly used to eliminate bacteria and algae by destroying it as well as chemically destroying other materials such as dirt and chloramines.