A lady stand next to DX50 Water Tank Treatment with a jug in front of a plastic water tank

How often should I treat my water tank?

This is a question we get asked a lot. Generally, for the average household, we’d recommend treating your tank water with DX50 about once a month during warmer months and every second month during cooler times.

However, there are many variables when it comes to treating water supplies, so please read on to understand some of the challenges you may face.

I’ve never treated tank water before. How do I start?

If you’ve never treated your tank water before, start by testing and monitoring both your tank and tap water for contaminants before and after applying your first dose of DX50. It is vital that your water is safe to drink.

Home water test kits primarily check for total coliforms and E.coli. For example, the total pathogenic protozoa concentration (i.e. Escherichia coli) must be less than 1 in 100 mL of sample.

You can purchase water test kits from our online store at https://dx50.co.nz/collections/home-water-test-kits. For a more detailed analysis, you can send samples to a water testing laboratory and compare against the drinking water standards here.


What if tests show my water is contaminated?

If your test results show that your water quality is poor know that, until you can make improvements to prevent contaminants entering your tank, you can safely add up to 10 times the recommended dose of DX50 and still be within safe limits.

Overtime, as your test results and required dosage become consistent, you can establish a regular water treatment routine that works best for your household.

While you can use DX50 at any stage, it’s important to note that the recommended dosage of DX50 Water Treatment will only kill microorganisms. It will not penetrate the body of dead birds or vermin that may be festering in your tank, so removing them and preventing other organic matter from entering your tank will be more effective.

This also applies to other disinfection methods and is especially important for those using harsher chemicals like bleach and chlorine which create carcinogenic byproducts when they react with contaminants. You can read more about this in our blog on how to sanitise water tanks: https://dx50.co.nz/blogs/news/how-to-sanitise-your-rainwater-tank


Is my water system okay?

Not all systems are equal, and there are many variables when looking at individual water supplies, including.


DIY bacteria test kit for water
  • how much organic matter is in your source water,
  • how it is filtered, stored, and distributed,
  • how fast you go through a full tank of water,
  • how often the tank is topped up,
  • and what seasonal or weather fluctuations might affect your water.

Think of it like housework – if you live in your home but don’t clean it, the unhealthier it gets. Even after cleaning, homes won’t stay clean and sterile for long. Germs, mould spores and bacteria are constantly around us, so reducing and preventing their growth is important for maintaining a healthy home and family.

Water tanks are the same. If you don’t prevent organic matter and other contaminants entering your tank, or you don’t clean your tank, or treat your tank water regularly, then germs and bacteria will grow. Once they enter your tap water your only line of defence will be your immune system.

Filters help prevent sediment passing through to your tap water, but too much contamination will weaken their performance and effectiveness. If not replaced in time, this will lead to bacteria growing through the membranes and into your drinking water. Therefore, filtration alone can’t be relied on to filter out and kill all harmful bacteria and protozoa like E.coli and giardia that may be in your water.

Why does the dose and frequency vary?

As every water system is unique, knowing your individual water system inside and out and how to treat your water is critical in your defence against harmful contamination.

 How your water is collected, filtered, stored, maintained, and used by your household will likely differ from your friends and neighbours. This is why the treatment dose and frequency can vary from one household to the next.

If you prevent debris from entering your tank, and there is low organic

equation on how much to treat your potable water with DX50

contamination in your source water, a standard dose of 50mls DX50 to 1,000L water should be all you need to kill any nasty bugs present. But if your system or water source is more heavily contaminated, then you may need to apply a higher dose, or treat your water tank more regularly.

Some households use more water than others, or their use might vary by weather and seasons. Some water tanks might collect a lot of roof debris from bird poo, leaves, dust, pollen, and then dump a viral load after the first rain of a dry summer. Other tanks are frequently topped up by rain in wetter regions or with bore water, adding fresh contaminants more frequently into the tank.

Often water tanks are plastic and sitting above ground, warming up in the hot sun, and providing ideal conditions for bacteria to grow. Others may be underground concrete tanks where the water stays cool and dark.

Add reminders to check your tank water in your calendar.

Calendar reminder to add Chlorine Dioxide into your tank at home

However your system is set up, it’s important that you add reminders in your calendar a to check and sanitise your water tank regularly. Check and test your tank water at least twice a year and treat your tank every month during spring and summer and bi-monthly over autumn and winter. This should avoid anyone getting sick from your tap water.

Make sure you also check all the other components in your water collection system and clean your rainwater tank of sludge build-up annually. If you have an older drinking water system, consider upgrading it to prevent contaminants entering your tank and becoming a health problem in your household.

A lady pouring Chlorine Dioxide Water tank treatment into her water tank

How can I prevent contaminants entering my tank?

In addition to regularly checking and cleaning your pipes, guttering and water tank, work out how you can optimise your system to ensure as few contaminants as possible enter your water tank.

Birds poo on a roof next to birdsWater that looks dirty and need treatment

Lots of factors can increase contamination levels in your drinking water, from bird poo washed by rainwater into your tank, farm effluent seeping into a bore, to leaves, debris and vermin washing into your tank from the roof. Once they’ve entered your drinking water, bacteria and germs can multiply especially in warm conditions.

A well set-up system with gutter guards, first flush diverters, filtration and a water sanitiser solution like DX50 Water Treatment will help ensure the safety of your drinking water. After all, the less contaminants and organic sediment there is entering your tank, the less sanitising solution you will need to add.

So, for example, if you collect rainwater from your roof, install leaf guards over your gutters and add first flush diverters to your downpipes and a vacuum overflow pipe to your tank, both of which you can get from your local hardware store. These prevent leaves, rodents, and other debris on your roof from entering your tank. Then install and replace your filters and treat and test your tank water regularly.

Description on all compounds in water tank connected to the house

To minimise rain stirring up sediment at the bottom of the tank, calm the entry of the rain by running a pipe down the inside of the water tank with an upward bend at the base. Then add a floating suction hose to the tank held about 15cms below tank water level by a ball float. This will ensure the fresher, more oxygenated water at the top of the tank is drawn first and the sediment remains undisturbed at the bottom of the tank.

These simple measures will help you to know what you’re dealing with. You’ll be able to determine where the contaminants are coming from, and what you can do to optimise your system and your dosing routine to get better results.

The Health Education website has some helpful information on how you can reduce contamination risk and improve the quality of your roof-collected rainwater. The booklet on Household Water Supplies also provides in-depth information on the selection, operation, and maintenance of your householder water system.

What if I can’t afford to upgrade my household’s water system?

purse almost empty with very little coins

For many properties, a system upgrade might not be possible or affordable. In these situations, your most cost-effective option is to test your water for contaminants and to routinely treat your water with DX50 Water Treatment.

Rest assured, until you can locate and mitigate the possible sources of contamination, you can safely dose your water with up to ten times the recommended amount of DX50. Your tank water will still be within recommended safety limits while being tasty, fresh, and clean to drink.

What if I supply water to a community?

A lady filling up a cup with water supplied from a community water scheme

If you are a water supplier, or an organisation that provides drinking water to others, (i.e. rural communities, schools, churches, community halls, camp grounds, etc.), you are required by law to provide potable drinking water that meets the new standards under the Water Services Act 2021.

Regardless of the nature of the source water used or the number of people served by the supply, the water you provide must comply within the maximum acceptable limits for organic and microbiological determinants.

Chlorine dioxide is a proven and globally used water treatment option for water suppliers. With its stronger oxidative power and a lasting residual, chlorine dioxide is often rated the better and safer sanitiser. Unlike chlorine, bacteria will not build a resistance to chlorine dioxide. Also, chlorine dioxide doesn’t create forever carcinogenic by-products in the treatment process, so it’s kinder than chlorine to the environment and your health. Furthermore, contrary to expectation given its compound structure, chlorine dioxide doesn’t leave a nasty chlorine taste or smell. For this reason and more, increasingly organisations are ditching chlorine in favour of chlorine dioxide.

Farm Road Water Supply is one such example here in New Zealand. They recently stopped using chlorine and upgraded their system to dose their bore water with DX50 chlorine dioxide.

How Farm Road Water Supply uses DX50 to treat their water supply

Farm Road Water Limited is a private water supply based in the Hawkes Bay with a wide distribution network that stretches tens of kilometres. Fifty-six farms and rural properties depend on the scheme for their drinking water.

To comply with New Zealand’s new drinking water standards and meet the minimum residual level throughout the network, the scheme faced either having to dramatically increase their chlorine dose or pay over $400,000 to upgrade their entire distribution supply to a UV and filtration system. After researching the options, participants elected to upgrade the system to use DX50 chlorine dioxide instead.

Co-founder Donald Strawbridge explained, “To achieve compliance throughout our distribution network, we would have had to significantly increase the chlorine dosage. With DX50 chlorine dioxide, we just use an automatic doser to add 50 mils per 1000 litres of water pumped. It is a lot less chemical than what we would have needed had we continued with chlorine, plus it’s a better sanitiser.”

Farm road water supply scheme automatic ClO2 dosing system and a map of the scheme

After talking with Water Force and DX50, Farm Road Water Supply implemented their new dosing and monitoring system using DX50 chlorine dioxide in March last year.

“The chlorine dioxide is automatically pumped from the DX50 container pod into the bottom of a sealed 2000L dosing tank. At the top of the tank is vent pipe which has a little one-way valve that, as the chemical is sucked out and injected into the water, allows air back in but nothing out. This relieves the pressure inside the tank. So far, we’ve not had any problems. Since switching to DX50 chlorine dioxide, tests show that we have good clean water throughout the system. It might be a little bit dearer than chlorine, but we don’t get the chlorine odour or taste, plus it’s noncorrosive. It’s a win-win for DX50,” said Donald.

Since the Farm Road Water supply scheme started dosing with DX50 chlorine dioxide, participants say the water tastes and smells great. Click here to read the Farm Road case study.

For more information about DX50 Chlorine Dioxide Water Treatment visit www.dx50.co.nz or call us on 0800 176 559.

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