Using roof or tank water

Public health topics Water Using roof or tank water

Roof or tank water quality may be affected by contamination and weather conditions.

For the latest information on water provision during the current dry weather – including the location of community water collection sites – visit Council’s OurAuckland website.

Many households in the Auckland region use roof water, bores and tank water supplies as their domestic supply or to supplement the water supply from the council. Householders need to know how to look after their roof, bore and tank supplies. There are steps you can take to ensure you and your family have access to quality drinking water and reduce the risk of water-borne illness from contaminated roof or tank water. See below.

Your water system should be installed by a qualified plumber, who can advise you on:

What you use the supply for (e.g. for all household water, supplementing municipal supply or outside use only)
Suitability of your current roof, gutters and pipes, and any improvements needed (such as first flush diverters and gutter protection)
Tank size, placement, pumps, filters and siphon equipment (which removes sediment from the tank bottom)
Any connection to the mains supply
Regular maintenance such as cleaning gutters, tanks and filters
Testing the water

Water filtration and treatment

Roof water and water tanks can easily be contaminated by animals faeces, dust, leaves, metals and other chemicals from the roof, and organisms growing in the tank.

Water filters are recommended, but there are several types, and you may need more than one filter, depending on water quality. We recommend having at least a 1 micron filter to remove bacteria and cysts of giardia and cryptosporidium. You may need other filters to improve odour and taste or remove chemicals.

If the water is prone to bacterial contamination, you should consider an ultraviolet (UV) treatment system, although they can be expensive. UV systems also need particle filters to ensure the UV works well.

Boil untreated water

Water should be boiled first if it is not from a reliable drinking water source. It is very important to use safe water for:

Hand washing. Use soap and water and dry your hands thoroughly. Hand sanitisers can also be useful if the skin is already visibly clean;
Washing fruit and vegetables and while preparing food;
Making infant formula.

Boiling a jug and letting it cool is sufficient to kill off bacteria, cysts and viruses. Cooled, boiled water can be stored in the fridge or a cool place.

Water supplies that are not suitable for drinking can be used for other things such as washing cars, watering plants, washing clothes and pouring into the toilet to flush.

Plan ahead - ensure you have access to enough water during periods of drought

For the latest information on water provision during the current dry weather – including the location of community water collection sites – visit Council’s OurAuckland website. Information about how to save and prioritise drinking water during water shortages is also available on the Ministry of Health website.

Households on roof or tank water may need to take measures to conserve water. For example, Waiheke Island has the lowest rainfall in the Auckland region and no piped water supply, so may run out of water in dry summers. People living in areas with low rainfall or no piped water supplies may wish to think about their water supply during periods of drought in advance.
If your water tank is empty, ensure you get it refilled using registered tankered water carriers. You can find a list of registered water carriers in the Auckland Region via the ESR Drinking-water for New Zealand website. It is important not to leave it too late to place your order, as allowing the pump to run when the tank is empty may cause damage. Delivery of water by a tanker will disturb the sediment lying in the bottom of the tank. Therefore, allow the water to settle and clear before using it for drinking, hand washing or cooking.

Pathogens (disease causing micro-organisms) can contaminate roof and tank water supplies, especially from animals which poo on the roof. Bacteria such as E. coli and Campylobacter and protozoa such as Cryptosporidium and Giardia are some of the pathogens that have been found in water from these sources. They can cause illness, such as diarrhoea, vomiting, stomach pains and fever. This can be particularly dangerous for infants, elderly people and people with a suppressed immune system.

Groundwater is usually higher quality than roof water, but ground water can become contaminated with bacteria, and chemicals including nitrate (NO₃). In areas with a high level of nitrate in ground water, there is a small risk to babies who are fed infant formula of developing a serious condition which affects how oxygen is circulated around the body.

Sources of groundwater contamination include:

Fertilisers and agricultural chemicals;
Animal wastes, particularly in areas of intensive farming;
On-site sewage disposal systems;
Industrial and food processing waste.

If you are using groundwater and live in an area of intensive farming or intensive fertiliser use, we advise having your water tested.

If you have any concerns about your water system talk with your plumber or council.

If you have concerns about water quality, get it tested by a registered laboratory

If you are concerned about your health, phone Healthline on 0800 611 116 or see your doctor or practice nurse.

ARPHS is involved in improving roof and tank water supplies through:

Registering water carriers and registering ground water sources used by carriers
Providing information to the public about water supply issues
Investigating outbreaks of gastroenteritis and other diseases related to drinking water

For the public