Two pathways. Lead, copper and nickel leach from plumbing — solder joints, brass fittings, and ageing pipes, especially in pre-1990s homes. Arsenic, uranium, iron and manganese are geogenic, dissolving naturally from the rock and sediment groundwater moves through.

There is no safe level of lead, particularly for children and pregnant women. Arsenic and uranium are naturally elevated in many Australian aquifers at concentrations that exceed health guidelines without any visible sign, taste, or odour.

Per- and polyfluoroalkyl substances enter water catchments and groundwater from firefighting foam, industrial sites, airports, and defence bases. They migrate slowly through soil and persist in the environment indefinitely — and standard municipal treatment does not remove them.

PFAS accumulate in the body over time and do not break down. The 2025 Australian Drinking Water Guidelines tightened limits for some compounds by up to 94%, meaning water considered safe a year ago may no longer meet the benchmark. They have no taste or odour at concerning concentrations.

A dual-purpose screen. Industrial solvents and fuel components — including BTEX, trichloroethylene (TCE) and tetrachloroethylene (PCE) — migrate into groundwater from petrol stations, dry cleaners, and historical industrial sites. Plumbing residues such as vinyl chloride and styrene leach from PVC pipe cements and adhesives.

Many VOCs are colourless and odourless at concerning concentrations, and several — including vinyl chloride — are recognised carcinogens. Solvent contamination can persist in groundwater for decades after the original source is gone, making it impossible to detect without laboratory analysis.

Organochlorine and organophosphorus pesticides and triazine herbicides leach through soil into groundwater, and run off into surface catchments, from agricultural land. Atrazine is among the most commonly detected chemicals in Australian agricultural groundwater.

Some organochlorines — such as dieldrin and DDT — persist in groundwater for decades after their agricultural use has ceased. These compounds are not removed by standard filtration and are relevant for any supply with agricultural land in its catchment or recharge zone.

Total Recoverable Hydrocarbons and Polycyclic Aromatic Hydrocarbons (PAHs) enter water from fuel and oil contamination, asphalt and bitumen roof runoff, proximity to industrial land, and bushfire ash washed into tanks and catchments.

Several PAHs, including benzo(a)pyrene, are carcinogenic. PAHs are not routinely included in standard residential water panels, yet they are a genuine risk for tanks with asphalt-shingle roofs or properties affected by bushfire — making them worth screening in a comprehensive audit.

Trihalomethanes (THMs) form when the chlorine used to disinfect mains water reacts with naturally occurring organic matter. Levels rise with water temperature, organic load, and distance from the treatment plant. On tank or bore water, these same parameters indicate broader organic loading.

THMs are an unavoidable trade-off of safe disinfection, but long-term exposure at elevated concentrations is linked to health concerns. They are also one of the most common reasons treated water smells or tastes "chemically."

Ammonia, nitrate, nitrite and total oxidised nitrogen enter water from fertiliser infiltration, septic systems, and sewage influence. In bore water they indicate agricultural recharge; in tank water, organic matter and animal waste in the catchment.

Elevated nitrate is a serious concern for households with infants, where it can interfere with oxygen transport in the blood. Nutrient levels are also a direct indicator of source water integrity and nearby contamination pressures.

E. coli and thermotolerant coliforms enter water from faecal contamination — animal droppings, leaking septic systems, surface water infiltration, or a compromised bore casing or tank inlet. Tank and bore water have no disinfection residual to suppress bacterial growth.

These are the standard indicators of faecal contamination and the single most important safety test for any untreated supply. Their presence signals a direct risk of gastrointestinal illness and a pathway for other pathogens to enter the water.

pH, conductivity, TDS, alkalinity, hardness and the major ions reflect the natural mineral content of your water and how it interacts with your plumbing. They vary with geology, treatment, and the materials your water contacts on its way to the tap.

This is the baseline characterisation that underpins everything else. Low pH accelerates metal leaching from pipes; high hardness causes scale in appliances; salinity affects taste and suitability. Together they explain corrosivity, scaling, and palatability.

Formaldehyde is a residual of certain plumbing materials and a by-product of chlorination, most relevant in newly installed or renovated plumbing. Fluoride is dosed to a controlled level in most city supplies, but occurs naturally — sometimes at elevated levels — in groundwater.

Fluoride is reported against the Australian Drinking Water Guideline of 1.5 mg/L — relevant for both excess (common in some inland aquifers) and the controlled levels in treated supply. Formaldehyde is worth confirming in any recently re-plumbed home.