Pool Deck and Patio Stone Cleaner

Steps

1. Sweep or blow loose debris, leaves, and dirt off the entire pool deck surface.
2. Dissolve the washing soda in 1 gallon of warm water in a large bucket, stirring until fully dissolved.
3. Add the castile soap and hydrogen peroxide to the bucket and stir gently.
4. Wet the deck surface with plain water from a hose to prevent the cleaning solution from being absorbed too quickly by dry stone or concrete.
5. Pour or mop the cleaning solution onto the deck in 4 to 6 foot sections, working away from the pool edge.
6. Let the solution dwell for 10 to 15 minutes. Do not allow it to dry — reapply to any areas that start drying.
7. Scrub each section with a stiff-bristle push broom or deck brush, paying extra attention to grout lines and textured areas where algae collects.
8. Rinse each section thoroughly with a garden hose. For a final step, mix 1 cup of white vinegar into a gallon of water and mop over the cleaned surface to neutralize any alkaline residue. Rinse once more.

Why It Works

Washing soda (sodium carbonate) creates a strongly alkaline solution with a pH around 11 that saponifies oils — including sunscreen, body oils, and tanning lotion — turning them into water-soluble compounds that rinse away easily. This is the same chemical reaction used in traditional soapmaking. Hydrogen peroxide acts as an oxidizer that destroys the chlorophyll in algae cells, killing the green and black biofilm that makes pool decks slippery and unsightly. Castile soap provides surfactant action, allowing the alkaline solution to spread evenly across textured stone and concrete rather than pooling in low spots. The vinegar rinse step neutralizes the high pH left behind by the washing soda, which is important because prolonged alkaline exposure can etch certain stone surfaces and leave a white haze on concrete.

Tips

• Clean the pool deck on an overcast day or in the evening. Direct sun causes the solution to dry too fast, reducing its effectiveness.
• For green algae in grout lines, apply undiluted hydrogen peroxide directly and let it bubble for 5 minutes before scrubbing.
• Avoid using this cleaner on natural marble or limestone. The alkaline solution can dull polished stone surfaces.
• Clean your pool deck every 4 to 6 weeks during swimming season to prevent algae from becoming established.
• A pressure washer on a low setting (under 1500 PSI) can replace the manual scrubbing step for large decks.