Sodium hypochlorite, the same chemical used to sanitise commercial pools and treat drinking water, is also one of the most effective and affordable ways to clean a patio. Diluted and applied correctly, it lifts black spot algae, moss, lichen and general grime from stone, concrete and block paving without heavy scrubbing. This guide covers how it works, how to apply it safely, and what to watch out for.
Why sodium hypochlorite works as a patio cleaner
The dark staining on patios is usually a mix of algae, moss and lichen rather than dirt. Sodium hypochlorite is a strong oxidiser: it breaks down organic growth at a cellular level, so the staining lifts away rather than just being scrubbed off the surface. This is why a chemical patio clean often looks better, and lasts longer, than pressure washing alone, since pressure washing can leave microscopic organic matter in the pores of the stone that regrows within weeks.
How to clean a patio with sodium hypochlorite
- Clear the area. Sweep loose debris and move plants, furniture and anything that could be damaged by splashes.
- Dilute according to the product label. Sodium hypochlorite for patio cleaning is used at a much lower strength than the concentrate is supplied at; always follow the dilution ratio on the product label and safety data sheet rather than guessing.
- Apply evenly. Use a garden sprayer or watering can with a rose to cover the surface, working in manageable sections.
- Leave it to work. Dwell time varies by product and level of staining, so follow the label guidance rather than rinsing immediately.
- Rinse thoroughly. Wash the area down with clean water, and rinse any nearby plants that may have been splashed.
Safety precautions
Sodium hypochlorite is corrosive at concentrate strength and should always be handled according to its safety data sheet (SDS). Wear gloves and eye protection, avoid mixing it with any other chemical (particularly acids or ammonia-based products, which can produce hazardous gas), and keep pets and children away from the area until it has been rinsed and dried. Work in a well-ventilated outdoor space and avoid application in direct, strong sunlight where the product can degrade and evaporate faster than intended.
What to avoid
Sodium hypochlorite can bleach or discolour some coloured paving, fabrics and nearby plants, so test a small, discreet area first if you are unsure. Avoid run-off into ponds, water features or drains where it could affect aquatic life, and never mix it with other cleaning products. If in doubt about a particular surface or a large commercial area, buy from a supplier who can provide a safety data sheet and talk you through the right product and dilution for the job.
Easy Chemicals Trade supplies sodium hypochlorite in a full range of pack sizes, from 20L poly containers for occasional use up to drums and IBCs for regular or larger-scale cleaning contracts, with trade pricing and nationwide delivery.
Frequently Asked Questions
Does sodium hypochlorite damage patio stone?
Used correctly and diluted according to the label, sodium hypochlorite is safe on most concrete, natural stone and block paving. Some coloured or porous stone can be affected, so always test a small area first.
How long should I leave sodium hypochlorite on a patio before rinsing?
Dwell time depends on the product strength and level of staining. Always follow the guidance on the product label rather than a fixed rule of thumb.
Can I use sodium hypochlorite instead of a pressure washer?
They solve different problems. Pressure washing removes surface dirt but can leave organic matter in the stone’s pores; a chemical treatment kills the algae, moss and lichen causing the staining, often with a longer-lasting result. Many professionals use both together.
Is it safe to use sodium hypochlorite near plants?
It can damage plants and lawns if it splashes or runs off onto them, so cover or move nearby plants where possible and rinse any that are accidentally splashed.
What strength sodium hypochlorite is used for patio cleaning?
We supply sodium hypochlorite at 14/15% concentrate strength, which is then diluted down significantly for patio and surface cleaning according to the product label.
Sodium hypochlorite is a proven, cost-effective way to bring a stained patio back to its original condition, provided it is diluted, applied and rinsed correctly. Buy it in trade quantities from Easy Chemicals Trade, with documentation and guidance available before you order.