Staining on fixtures and in laundry is the most visible symptom of a water quality problem, and its colour identifies the cause.
Orange to reddish-brown
Iron.
Whether it arrives clear and turns orange on standing (ferrous, dissolved) or is already orange at the tap (ferric, particulate) determines the treatment — a softener handles small amounts of the first and neither handles the second, which needs filtration.
Concentrations of a few tenths of a part per million are enough to stain.
Black to dark brown
Manganese, usually alongside iron.
It needs oxidation and filtration like iron, generally at a higher pH, which is why a pH correction stage sometimes precedes it.
Slimy orange or brown growth
Iron bacteria, in the cistern, the well and the plumbing. It has an earthy or oily smell.
Filtration does not address it because the organism grows within the system. Shock chlorination of the well, repeated, and continuous disinfection where it recurs.
Blue-green
Copper, dissolving from the plumbing.
That is not a source water problem; it is acidic water attacking the pipes. The treatment is pH correction at the point of entry, and the stain is a warning that copper is entering the drinking water.
Test for copper and lead, first-draw from a tap, and correct the pH.
White, chalky
Hardness, deposited as scale on fixtures, glassware and shower screens.
Softening or a salt-free conditioner, depending on which of the two objections the household actually has.
Yellow-brown in laundry, worse over time
Frequently iron accumulating in fabrics over many washes.
Ordinary detergent does not remove it and chlorine bleach makes it worse — chlorine oxidises iron and sets the stain. A rust remover formulated for the purpose, or an oxalic-acid-based product, is what lifts it.
That single fact — bleach sets iron stains — is worth knowing, because the instinctive response makes the problem permanent.
Removing existing stains
On fixtures: acidic cleaners for hardness and mild abrasives, and rust-specific products for iron. Avoid chlorine on iron stains.
On laundry: rust remover, not bleach.
In toilet cisterns: cleaning the growth out and addressing the well, since it will return otherwise.
None of this is treatment. It removes the evidence and the water continues to deposit more until the source is dealt with.
The order to work in
Test. A laboratory panel giving iron, manganese, pH, hardness and bacteria.
Match the treatment to the result, not to the stain — because orange stains come from three different iron problems with three different remedies.
Install in the correct sequence, with the softener last.
Retest afterwards to confirm it worked.
The stain that is not a water problem
Pink or orange film in a shower or a toilet, appearing over days and wiping off easily, is usually Serratia marcescens, an airborne bacterium that colonises damp surfaces.
It is not in the water supply and no treatment equipment will address it. Cleaning and ventilation will.
Protecting laundry while the treatment is planned
Iron stains build up in fabrics over many washes, and once set they are hard to lift.
Two interim measures: an iron-removing laundry additive with each wash, and avoiding chlorine bleach entirely. Neither is a solution and both prevent months of accumulating damage while the equipment is being specified.
Where the iron is coming from
Not always the aquifer.
A corroding steel casing or old galvanised plumbing contributes iron, and the symptom is the same. A well log giving the casing material, and the age of the house's pipework, are worth knowing before assuming the ground is the source.
Where the plumbing is the source, a whole-house iron filter treats the water arriving and does nothing about the iron added afterwards — which is why the sample point matters when testing.
After treatment is installed
Retest, and check the stains stop appearing on freshly cleaned fixtures.
A filter that reduces iron from 5 ppm to 0.5 ppm has removed 90% and will still stain, because the threshold for visible staining is very low. The target is the secondary limit, not a percentage reduction.