Water testing

Testing Drinking Water - Surface Water

For those customers who collect their drinking water from surface water who are wanting to check whether it is safe to drink.

 About this Testing

Surface water comprises water from springs, streams, rivers and lakes. Surface water quality will vary greatly (especially water from streams and rivers) depending on rainfall run-off and the land use of the surrounding catchment. It will always require treatment if it is to meet the requirements of the New Zealand Drinking Water Standards as Ecoli will be found due to faecal matter of mammals.

Testing surface water is covered by our Routine Water profile:

Test

Typical Range

NZDWS 2005 Maximum Acceptable Value (MAV)

Comment

pH

5.5 - 7.5

7.0 - 8.5 (Guideline Value)

Surface water that is low in pH can attack copper piping leading to high levels of dissolved copper

Conductivity

NA

<1500us/cm

Important for ion balance check and other parameter estimation. Used to calculate TDS.

Turbidity

NA

<2.5 NTU

Appearance. For effective terminal disinfection <5 NTU (single sample)

TDS

10-500mg/L

<1000 mg/L

Water that is high in TDS can have taste problems.

Alkalinity

NA

NA

Important for interpretation and other parameter estimation

Calcium

NA

NA

Major ion, used to calculate hardness.

Magnesium

NA

NA

Major ion, used to calculate hardness.

Hardness

0.1 - 2 mg/L

<200 mg/L

High hardness may cause scale deposition and scum formation. Water with low hardness (<100) may be more corrosive.

Sodium

NA

<200 mg/L

Major ion, can cause taste problems

Potassium

NA

NA

Major ion

Nitrate

NA

<11.3 mg/L

Important nutrient indicative of fertiliser application and other anthropogenic inputs, health concern (can cause methaemoglobinaemia in bottle fed infants)

Chloride

NA

<250 mg/L

Major ion, can cause taste and corrosion problems.

Sulphate

NA

<250 mg/L

Major ion, can cause taste problems.

Arsenic

NA

<0.01 mg/L

High levels of Arsenic indicate geothermal input.

Boron

NA

<1.4 mg/L

Indicative of Geothermal sources.

Iron

0.1 - 2 mg/L

<0.2 mg/L

High iron is not a health issue, but can lead to staining of laundry and sanitary ware

Manganese

<0.05 mg/L

<0.04 mg/L

<0.10 mg/L

<0.4 mg/L

Staining of laundry

Taste Threshold

Health MAV

Copper

NA

<2 mg/L

Can be leached from copper piping by acidic/corrosive water.

Zinc

NA

<1.5 mg/L

Can be present due to galvanised metal piping.

EColi

Usually Detected

<1 in 100mL of sample

Always an issue for surface waters

 

Taking a Sample

In terms of where to sample, it is very important to have a clear idea of what information you are trying to obtain. For example, if you are only interested in the quality of water coming out of your kitchen tap, then the sampling should take place there. However, if you have installed treatment and you want to find out how effective it is, then you may want to take 2 samples - one from the tank (pre-treatment) and one from the kitchen tap (post-treatment), and 2 sampling kits will be needed.

It is not usually advisable to take a sample from a river or stream as it characteristics can change so much. Ideally the water should be pumped into a reservoir and this should be where the sample is taken from. However if there is no reservoir in place, try to sample when the stream or river is in its most common state.

When taking the sample, it is very important to follow the instructions provided, especially for the Ecoli test. This requires a sterile container (square plastic 400mL) and the tap needs to be sterilised to make sure that no contamination occurs. Also note that we need the samples back with 24 hours and less than 10°C, otherwise the results will not be valid. For clients who are not within easy driving distance from Hamilton or Christchurch, we suggest taking your sample in the early afternoon and sending it overnight to the laboratory. When sampling from a stream or river, face the container upstream and allow to fill gently until it is full.

Unsure about the correct container to use to submit a sample? Consult our container catalogue
Sampling equipment:

Request a Routine Water Kit from the Laboratory. It contains 3 sample containers which are all required for one test, i.e. they should all be filled from the same sampling point, not from 3 different points.

Guides and Supporting Information:

 

Contact Us

Freephone 0508 HILL LAB (44 555 22) or email Env.CSM@hill-labs.co.nz