What to Do If My Swimming Pool Stairs Are Yellow?

The appearance of yellow spots around the stairs of your swimming pool can indicate that something is happening with the chemistry of the pool water. To keep the pool water as clean and healthy as possible, a proper diagnosis and quick treatment of the problem are necessary. Yellow discolorations typically point to algae growth or iron deposits.

Little girl in swimming pool
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Clean stairs are not slippery and are much safer than those covered in yellow algae.

Yellow Algae

If the stairs of the swimming pool are turning yellow, you may have mustard algae. Mustard algae typically grows in the shade and may also cling to the sides and bottom of the pool. It is one of several different types of algae found in swimming pools, and when the slippery substance forms on stairs, it makes for a treacherous climb in and out of the water. Determine if this is the cause for the yellow hue by trying to scrub the yellow spots away. If they disappear with scrubbing but are back within a few days, mustard algae is the culprit. Sometimes loosening the algae with a brush and then shocking the pool is will fix the problem. If not, visit your local pool supply store and pick up an algicide. Keep your filter running at all times and keep your pool water at the proper pH and chlorine levels.

Mineral Buildup

When there is too much of a mineral present in the water, it can begin to stain the pool. Shades of yellow can be a sign of excessive iron. Iron can be introduced into a pool by well water or pipe corrosion somewhere in the pool system. Unlike algae, iron deposits resist scrubbing and take a lot of elbow grease to remove. A simple water test will confirm the presence of iron in your water.

To correct the problem, allow the chlorine level in your pool to drop to 0 ppm. Lower the pool's pH level to 6.8 and then add one quart of iron remover for every 5,000 gallons of pool water. Leave the pool sit overnight with the filter running. Raise the pH level back to between 7.2 and 7.8 and then resume your regular chlorination routine. Vacuum out any iron particles that settle to the bottom of your pool during this process.


Doing a little preventative maintenance is much easier than trying to overcome algae or iron problems. Preventive maintenance will stop your stairs from turning yellow and help manage other potential problems.

  1. Clean the pool filter frequently since dirty filters can reintroduce problems you've already solved.
  2. Keep a close eye on pH and chlorine levels as well, especially if you are filling your pool with well water.
  3. Remove any debris as soon as it falls into the water, as leaves can bring algae particles with them into the pool.