The Well Water Lab Stain Color Key

The Stain Color Key is a short reference that The Well Water Lab uses to describe the stains that well water can leave on fixtures, sinks, tubs and laundry. It sorts stains into four colors and pairs each color with the water constituent that is most often associated with it. The key gives a homeowner a first vocabulary for what is seen, so the stain can be described clearly to a laboratory or a water professional. It is written for people with no laboratory background.

What it is

The Well Water Lab Stain Color Key has 4 items and its 2026 reference code is WWL-SCK-xiax. The key has four entries, one for each stain color. Each entry names a color as it looks on a porcelain or metal surface and the constituent most often linked with that color. Different constituents can leave similar marks, and more than one can be present at the same time.

The items

• Orange-brown: most often associated with iron.
• Black: most often associated with manganese.
• Blue-green: most often associated with copper picked up from low pH water.
• White: most often associated with hardness minerals, seen as a crusty or chalky deposit.

How to use it

Look at the stain on a clean, dry surface in good light. Match its color to the closest entry in the key and write down where it appears, such as under a faucet, in a toilet bowl or on laundry. Note whether the stain is at hot water fixtures, cold water fixtures or both. Use the matched constituent as a starting point when choosing which analysis to ask a laboratory for.

Limits

The key matches colors to constituents that are commonly associated with them. It does not identify what is in a particular well. Only a laboratory analysis of a water sample can do that, and the key should be read as a way of describing a stain, not as a result.