Jeyes 4 in 1 patio power 4 litre kills and prevents re growth of mould algae and mildew on all hard outdoor surfaces including patios paths driveways stone and concrete simply dilute the formula with water 9 parts water for light growth or 4 parts water for normal growth the formula works instantly with visible results in killing mould and algae within 1 3 days continues cleaning for several weeks black mould covers up to 198mwarningcauses skin irritation and serious eye damage ke