Drinking water - hard or soft
Gisborne District Council's reticulated water supply to city residents always complies with the Drinking-Water Standards for New Zealand 2005 (Revised 2008)(external link) .
In a water emergency or if we're experiencing drought conditions and water restrictions are put in place, we'll supplement the water supply with water from the Waipaoa River.
When we do this, residents may notice a difference in taste due to the different water source, but the water is safe to drink.
The Tāirawhiti District Public Health unit acting on behalf of Ministry of Health can verify this.
Is our drinking water hard or soft?
The water supplied from the Waingake water catchment (Mangapoike dams) can be described as 'soft water'.
The water supplemented from the Waipaoa River to the council supplied water can be described as 'hard water'.
Soft water has less calcium and magnesium, while hard water has high calcium and magnesium.
Some effects of hard water, with high calcium and magnesium
Hard water makes it difficult to lather up soap and the minerals form a residue that makes it harder to rinse items.
This includes your hair, dishes and glassware in your dishwasher may be left with a white chalky scale or water spots.
A long-term effect is it can cause scale to develop on the inside of pipes.
If the hard water is affecting your clothes, dishes and dishwasher, or your hair feels sticky and dull, here’s some home remedies to try:
- place a small dish filled with lemon juice, vinegar or baking soda on the top rack of the dishwasher during a cycle. Another tip is 1 teaspoon of citric acid in with the detergent.
- descale your electric kettle - boil some white vinegar.
- for your hair - use a rinse of one table spoon vinegar or lemon juice to three parts water.
- some laundry detergents are better for hard water or have different instructions for how much you should use. Check the label on your powder or detergent.
- reduce the temperature of your hot water cylinder can reduce the amount of mineral build up in pipes.
Is hard water safe to drink?
Yes it's absolutely safe to drink.
Regarding public health opinions: The water is compliant with the very stringent NZ Drinking Water Standards.
Questions have also been asked about the quality of the water from the Waipaoa River. An extensive one year (26 sample) raw water cryptosporidium testing programme was conducted on the Waipaoa River in 2010-11 . This testing was approved by the local Drinking Water Assessor acting on behalf of the Ministry of Health. The treatment processes that we apply to the water from the Waipaoa River, based on the quality of water found in the extensive sampling, complies with the drinking water standards.
There is an approved Public Health Risk Management Plan in place for each of our water treatment plants, addressing every risk aspect of the source extraction, treatment process, disinfection and delivery to the customer.
What is hard and soft water
The sum of all calcium and magnesium compounds in water results in the total hardness, measured in milligrams calcium carbonate per litre (CaCO3 mg/L)
The water supplied to Gisborne from the Waingake Water Catchment has a total hardness level of below 100 mg/L of calcium carbonate CaCO3 and can be described as soft. It typically ranges between 30-70mg/L CaCO3
The Waipaoa River water is higher with a CaCO3 equivalent concentration greater than 120mg/L are considered to be hard and the combined hardness levels of the Waingake and Waipaoa treated water measured where it enters the city is generally between 100-180mg/L depending on water demand.
Water hardness is described as an "aesthetic determinand" in the Drinking-water Standards for New Zealand 2005 (Revised 2008). This means a property that can adversely affect taste, colour or general appearance of water. Guideline values (GV) are applied to aesthetics – these are levels that if exceeded, may make the water unattractive to consumers. The GV for total hardness is 200mg/L CaCO3