Private water supplies
Knowing where the water you drink, wash your food, and bathe in comes from is important.
It will help you protect you and your family and friends from the chemicals or bacteria that may make the water unsafe.
Unsafe contaminated water can cause serious illness (vomiting and diarrhoea) and even be life-threatening for infants, older people, or people with weak immune systems.
If water comes into your taps from a private water supply such as a groundwater well, a roof rainwater collection tank or a stream, river, lake or spring, then you’re responsible for understanding the quality of this water and how to keep it safe for use.
If you notice changes in the colour, odour, or taste of your water or that it is suddenly cloudy, then your water may be contaminated and you need to get it tested by a qualified laboratory water treatment expert.
On this page you’ll find information to help you:
Rainfall or river water that naturally seeps into the earth becomes groundwater. Groundwater quality is influenced by the geology it flows through which means that natural impurities can end up in your well water supply.
Chemicals and bacteria from overlying land can also flow with the water as it moves from the earth’s surface into groundwater. While the time the water takes to filter through soil and gravel can help reduce these contaminants, there’s still a risk of bacteria and chemicals from farming, gardening, landfills, storm water drains, septic or fuel storage tanks entering your well water.
Sometimes even water from irrigation or soak pits can become groundwater too.
Streams, river, lakes and springs are surface water sources that can also be affected by factors like those that effect groundwater.
Contamination and bacteria can also flow into streams, rivers, and lake water through a storm water pipe or run off from land. Unlike groundwater, surface water isn’t filtered by the soil.
Roof water collection can become unsafe when leaf litter, debris, animal droppings from birds and possums or even dead animals and insects build up in gutters or water tanks.
Additional factors that can also contaminate roof water include:
Make sure your well head (top of the well) is above the ground’s surface where it will not be at risk of being flooded. You should also have a good seal around the well where the well casing emerges from the ground to stop surface water running down the side of the well casing.
Keep the well cap closed tightly to prevent surface water, animals or contaminants from getting into the well. Make sure that your well also has a backflow preventer which will stop pumped water flowing back into your well.
We also recommended that you filter and treat well water before you drink it. Well water can easily be tainted by contamination sources hundreds of metres away from the well.
Well construction – in particular it's worth finding out:
These details are recorded in a driller’s log prepared at the time the well was drilled and will help you understand where water is coming from, what type of geology it flows through, and if the well has been constructed correctly to prevent contamination from entering the well.
Unwanted wells must be properly decomissioned or sealed to prevent contamination entering groundwater.
If you do not decommission an unwanted bore on your property you can be fined. Your local driller can provide advice on decommissioning and keeping your well secure.
It can be hard to prevent streams, rivers and springs becoming contaminated by factors further upstream that you don’t know about.
To reduce bacteria risk to your surface water supply collect your water as close as possible to origin of your source. For example in headwaters of a river or stream where there are less impacts from humans or animals. Fence off the area surrounding your water collection point to stop animals from entering your water supply.
Because streams, rivers and springs are easily accessed by animals or impacted by upstream activities, we recommend that you filter and treat water before drinking.
You can find more information on the HealthEd website.
We encourage you to:
It's your responsibility to ensure the water is safe before use. Look for changes in water colour, odour, taste, or a sudden cloudy appearance can suggest that water contamination is occurring in your supply.
The best way to check for potential water quality issues is to collect a water sample and have this tested by an independently accredited IANZ laboratory.
Every drinking water supply should be tested annually at a minimum to make sure it is safe to use.
You will need to consult a qualified water treatment expert on water treatment options that are appropriate for your water supply.
Visit International Accreditation New Zealand (IANZ) for any information on testing and for a list of Ministry of Health accredited laboratories that may be able to test your water supply.
Contact your District Council of Public Health Unit for advice on:
Contact our environmental science team for advice on: