Water testing

Testing Drinking Water from a Bore

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

About this Testing

Many people use bore water (ground water) as a drinking water source. While it is possible to characterise the water from a particular aquifer in general chemical terms, it is always advisable to check the water from a particular bore as it can be affected by local inputs of contaminants. In fact, if the borehead on the well is not sealed properly, soil and other debris can enter the well and cause contamination, especially of a biological nature.

Testing bore 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)

Groundwater 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.

TDS

10-500mg/L

<1000 mg/L

Bores close to the ocean can have elevated levels. Water from limestone aquifers can also be high in TDS.

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, indicative of salt water intrusion, 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, indicative of salt-water intrusion, can cause taste and corrosion problems.

Sulphate

NA

<250 mg/L

Major ion, can cause taste problems.

Boron

NA

<1.4 mg/L

Has been detected in some bores from 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

Not Usually Detected

<1 in 100mL of sample

Generally not an issue for groundwater but can be detected in shallow bores

Pesticides (optional)

Not Usually Detected

Aldrin + Dieldrin < 0.00004 mg/L

Atrazine < 0.002 mg/L

Dieldrin has been detected in some bore waters, thought to originate from old sheep dips.

Triazine herbicides such as atrazine, propazine and hexazinone have also been detected from horticultural use.

 

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.

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.

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

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