How Often Do New Zealand Schools Need to Clean Their Water Tanks?

Here in NZ, managing water supplies, including water tank maintenance for schools, follows specific guidelines to ensure water quality for both staff and the kids. Unlike years ago, the old ‘she’ll be right’ attitude won’t meet the water regulation requirements . . .

Legal Obligations

Under the Water Services Act 2021, schools, as drinking water suppliers, have a legal duty to ensure the safety of the water they provide. This includes developing and implementing a Drinking Water Safety Plan (DWSP) that outlines risk management strategies and compliance with the Drinking Water Quality Assurance Rules. 

Schools must also meet the Drinking Water Standards for New Zealand, which set maximum acceptable values for various contaminants and aesthetic qualities like taste, smell, and appearance of drinking water.

These standards can all be addressed as per the details below:

UV and Sediment Filtration

Under the water regulations, one of the main requirements of schools is to have a validated UV filtration in place.  Validated systems simply put, measure the power output of the UV bulb and the flow rate of the water going past the UV bulb. This is to ensure they are within the specifications that allow the UV light to do its job of neutralising bacteria.  The units will stop and alarm if the required specifications are not met.  

The combination of the sediment filters and UV treatment will remove and/or neutralise most organisms that are dangerous to human health, as long as the source water is clear enough.

For the filtration system to work to its optimum, it requires the water to be free from suspended sediment as this impacts the effectiveness of the UV light accessing the bacteria to neutralise them. Sediment filters act as a barrier, trapping a myriad of sediment and organic matter and should be installed with a UV filtration system. Consequently, regular tank cleaning combined with UV + Sediment Filtration provides the best protection and opportunity for clean and safe water for all users.   

Water Sources

There are typically two different water sources – rainwater or groundwater (bore/surface water). They each need separate consideration. 

Rainwater 

Schools using rainwater as a water source should ensure that debris from roof catchments getting into their water tank(s) is minimised. This can be ensured through regular roof and gutter cleaning, and the installation of gutter whiskers or leaf guards where relevant.  First flush diverters could be considered, but opening flushing caps on the water feed pipes during rain events works well to minimise the worst of the debris from your roof entering the water storage tanks.   

Additionally, regular inspection of the water pipes feeding the tank(s) itself to ensure they are water and airtight prevents animal and insect intrusion.   

All the above steps will help minimise the organic material that enters the water tanks, but it should be noted that nothing will stop the sediment build up over time.  This sediment can provide a breeding ground for bacteria to grow and thrive in. So, the above steps, combined with regular maintenance tank cleans, collectively reduce the risk of contamination in the tank(s), sediment build up, and the UV filtration inadequately doing its job. 

Read more on the Ministry for Education website. 

Groundwater 

Groundwater supplies include bores and/or stream/spring/surface fed sources. 

As these sources contact the earth they can and do pick up elements such as iron, manganese, or bacteria from the ground. A water chemistry and microbiological test of the source water is required to determine what exactly the make-up of each groundwater supply is. This will determine if pre-treatment is required for the water source before entering the storage tank. This water test results will be compared to NZ Drinking Water Standards and will ascertain if the water is within the required specifications for UV filtration to function.  A common example relating to NZ bore water is the presence of iron and manganese.  If these elements are present above a certain concentration, they will render UV filtration ineffective.  Therefore, the water would need pre-treatment to remove the elements prior to storage.  

Other considerations for groundwater sources are ensuring bores and surface water catchments are suitably secure to minimise the risk of contamination at the source. The requirements vary depending on the source and its surroundings. 

Read more on the Ministry for Education website. 

Regular Maintenance Schedule

Schools should clean their water tanks regularly to remove sediment and other contaminants that will accumulate over time. Ideally this should be done annually and from our experience of cleaning thousands of tanks per annum, at least every two years, to minimise the contamination risk and ensure that the required UV filtration can work effectively.  

In conjunction with the above, regular checks of the water supply and its security should be completed, as per the elements listed above, to minimise contaminants entering the water tank(s). This includes: 

• Checking sediment levels and water clarity (remembering that the human eye cannot always see what is in the water) 

• Making sure that all seals are intact 

• Ensuring there are no holes or openings in and around the tank(s) and pipes. 
• For rainwater fed tanks, keeping the gutters and roof clean and clear of overhanging vegetation can minimise the amount of organic material getting in your tank(s)

The sediment filters should be changed approximately every 6 months, and the UV bulb should be changed annually.  The internal workings of the UV system should be cleaned at the same time as the bulb is changed to ensure any biofilm build-up is not reducing the effectiveness of the UV bulb. 

Monitoring Water Quality

The ultimate test of whether your water system is operating effectively and safely is to test the water quality regularly.   This means regular microbiological water testing at various sources around the school.  Importantly, this task should include having an emergency plan in place if a positive test is returned – both for actions to isolate the supply and protect the users and to identify and treat any issues with the supply.  

If water quality tests indicate contamination, immediate cleaning and disinfection are necessary before retesting is undertaken.

Using Water Tank Cleaning Professionals

Schools will benefit from using professional water tank cleaning services, such as Safe H2O, to keep tanks clean. Simply flushing tanks does not clear the sediment collected on the bottom of the tank and requires specialist tools. 

The Safe H2O services can include detailed inspections, complete cleaning, and disinfection procedures that comply with water safety standards in Aotearoa. Read more here about the benefits of using a tank cleaning specialist.    

For more detailed guidelines and resources on water tank maintenance, visit Taumata Arowai, or feel free to reach out to our team for a free consultation.