What are the NZ guidelines for my water?

Please use this guide to help describe the problems you are experiencing with your water. 

CONSTITUENT

GUIDELINE VALUE (mg/L)

MAXIMUM ACCEPTABLE VALUE (MAV)

REMARKS

Total Solids

500

1000

The total dissolved solids consist mainly of inorganic minerals. Excessive TDS levels affect taste. Below 500 g/m the taste is usually good but water becomes increasingly unpalatable above 1000.

Turbidity

1 NTU (<0.5 for

Giardia removal

by coagulation

and filtration

10NTU

Suspended matter causes cloudiness (turbidity). It is recorded as Nephelometric Turbidity units.

Excessive levels can protect micro-organisms from disinfection with chlorine and can be a source of nutrients staining when washing fabrics.

Colour

5 H

10 H

True colour is caused by dissolved coloured substances (apparent colour includes the effect of coloured turbidity). Colour is derived from decayed vegetation. It is measured in degreed Hazen. Excessive colour produces laundry and other staining.

Substances causing odour and taste

Inoffensive

to most

consumers

Inoffensive

to most

consumers

Tastes and odours have many sources such as fungal or algal growth, henolic substances (e.g. bitumen) or the effects of chlorination.

pH Expressed on
pH Scale

7.4 – 8.5

6.5 – 8.5

Low pH levels can cause corrosion of metals in the distribution system. A high pH will reduce the effectiveness of chlorine disinfection and can cause scaling problems.

Total hardness as CaCO

80

200

Total hardness represents the calcium plus magnesium content. Excessive hardness can scale piping, heating elements etc and cause washing problems. Very low hardness levels can render water corrosive.

Calcium as CaCO

See total

hardness

See total

hardness

Calcium is a component of total hardness Low levels can make waters corrosive but this effect is greatly influenced by other factors particularly pH, alkalinity and the presence of salts such chlorides or sulphate High levels cause scaling.

Magnesium as

CaCO

See total

hardness

200

Magnesium is a component of total hardness. It is a laxative in the presence of sulphate (Epsom Salts). When over 250mg/L sulphate is present, the Magnesium content should not exceed about 30

Sodium

100

0.15

Sodium affects taste. Most users detect saltiness about 200mg/L. High levels not suitable for young children or with some diets.

Aluminium

 

 

Orally ingested aluminium is associated with Alzheimer’s disease. Great care must be taken with some special medical applications such as kidney dialysis units. Aluminium compounds (e.g. alum) are commonly used for water purification

Silver

 

 

Not hazardous at practical levels

Arsenic

 

0.01

Most arsenic compounds are poisonous and generally enter water from timber preservatives

Lead

 

0.01

Lead is most likely to be sourced from lead pipe work with aggressive water (low pH or low hardness).

Iron

0.1

1.0

Iron is common in bore waters or as a contaminant derived from the corrosion of steel pipes etc. Reddish-brown iron sediments cause discolouration of washing, stained basins etc, deposits and bacterial slime. High iron levels can effect taste and alter the colour of prepared drinks and food

Manganese

0.05

0.5

Manganese is common in bore waters. It gives similar problems to iron, the deposits being black or dark brown.

Copper

 

2.0

Copper in water rarely occurs naturally. It usually indicates corrosion of copper pipes or tanks. The levels encountered in drinking water are generally non-toxic to man. Above 5mg/L the water becomes blue and has bitter taste. Blue staining of fixtures is the usual indication of the presence of copper

Nitrate

25

50

(as NO)

Indicates contamination by fertilizers. Causes ‘blue baby’ problems (metahemoglobinemia)

Boron

 

0.3

Low levels of Boron have been associated with testicular atrophy. Appreciable boron levels are

usually only found in deep bores

Chloride

100

250

Chloride affects taste. Most users detect saltiness in the 200-300mg/L range. The guideline values are based on taste, not health hazards. High chloride levels make water corrosive. Chloride is a major component of sea water

Fluoride

Recommended

range after addition 0.7 1.0

1.5

Fluoride is added to many supplies to promote dental health. The natural levels in NZ waters are mostly less than 0.2mg/L 1.0 Fluoride can damage teeth at high levels.

Sulphate

50

400

Sulphate has a laxative effect at high concentrations, particularly in presence of magnesium. The guideline values are based on taste. High sulphate levels render waters corrosive

Sulphide

Not detectable

to most

consumers

 

Sulphide in the form of hydrogen sulphide can produce an unpleasant flavour in ground water devoid of oxygen. Levels as low as 0.5mg/L produce taste but the smell is evident at much lower levels. Sulphide can originate from geothermal activity or from the bacteriological reduction of other sulphur compounds.

Organic

compounds

Many compounds

have individual

MAV levels

 

Numerous organic compounds are found in water derived from both natural sources and pollution. Organic substances often affect flavour particularly after chlorination or are carcinogenic e.g. THM’s produced by the action of chlorine on natural organic compounds.

Zinc

 

3.0

Zinc usually results from corrosion of galvanised or brass pipes etc as it rarely occurs naturally. It is not a human health hazard but may be poisonous to fish. Above 5mg/l may cause taste and cloudiness