Two of the most common water quality complaints we hear from bore owners are reddish staining on laundry, fixtures, and concrete, and water that tastes increasingly salty as the years go on. Both problems have well-understood causes, both can be managed, and neither is a reason to abandon a bore that has otherwise served you well. Knowing what is actually happening below ground is the first step to fixing it.
Darr Drilling has been working with Queensland bore water for more than 40 years. Iron and salinity issues come up across the entire region we cover, from the Maranoa through to the Darling Downs and beyond. This guide explains what causes each problem and what practical options you have.
The Short Version
Iron staining usually comes from dissolved iron in the groundwater reacting with air, often made worse by iron-oxidising bacteria that grow on bore screens and pumps. Salinity reflects what is dissolved in the aquifer. Iron can be treated and rehabilitated. Salinity is harder to change but can be managed through bore design and use. Both benefit from early intervention.
What Causes Iron Staining
When groundwater carries dissolved iron, it stays clear and colourless underground because oxygen levels are low. The moment that water reaches the surface and meets air, the iron oxidises and forms a red, brown, or ochre precipitate. That is the staining you see on fittings, in toilet bowls, on laundry, and on concrete. Bore water that comes out sparkling clear and then “muddies” in the tank or trough overnight is a classic iron signature.
The problem compounds when iron-oxidising bacteria get into the bore. These bacteria, often Gallionella and similar species, feed on dissolved iron and produce a slimy rust-coloured biofilm. The slime coats bore screens, pump impellers, and the inside of casings, restricting flow and overheating submersible motors. Once a bore is biofouled, the bacteria are very difficult to eradicate entirely.
What Causes Salinity
Salinity in groundwater reflects the geology of the aquifer. Some formations carry naturally high dissolved-solids loads, particularly where groundwater has moved slowly through marine sediments or where evaporation concentrates salts. Salinity is measured as Total Dissolved Solids (in milligrams per litre) or as electrical conductivity (in decisiemens per metre or microsiemens per centimetre).
Salinity often increases over the life of a bore as standing water levels drop and the well draws from deeper, more saline horizons. Surface water sources also rise in salinity through summer evaporation, which is one reason bores tend to be more salinity-stable than dams or tanks during dry runs.
Tolerance Levels by Use
How iron and salinity affect different uses
Household and domestic use
Iron staining of laundry, fittings and tiles. Salinity affects taste, kettle scale, and plumbing longevity.
Stock water
Iron is generally tolerated. Beef cattle production decline begins at around 4,000 mg/L TDS, with absolute limits significantly higher.
Garden and irrigation
Iron clogs drippers and stains pavers. Salinity affects soil structure and plant tolerance, especially on sensitive crops.
Pumps and equipment
Iron biofilm overheats submersible motors. Saline water accelerates corrosion of steel components.
Practical Steps That Help
When to Rehabilitate vs Replace
Most bores with iron problems respond well to rehabilitation. High-volume compressed air, chemical cleaning compounds, and physical brushing can clear biofilm, restore screen open-area, and recover lost yield. We handle this work through our bore rehabilitation service and our cleaning service for new and existing bores. Replacement is the right answer when the casing itself has failed, when the screen is deeply corroded, or when geology has changed enough that a different bore design would serve you better.
Salinity is rarely fixable by working on the bore. Where salinity has risen, the practical responses are to adjust pump placement, redesign the screen to draw from a different horizon, or in extreme cases drill a separate bore for a different aquifer.
Getting an Honest Assessment
If your bore is staining, slowing, or showing changes in water quality, an inspection is the right first step. You can contact our team, look at our maintenance service, or read our background information on the about us page.
