Our flagstone patio is about 6 years old and was not sealed. With all the rain we have had..it has developed a green film. How can I safely clean it???
go to home depot and get a gallon of cleaner called Krudcutter.mix with water(read directions)and apply with a stiff bristle deck brush.let it set for a while and rinse with a garden hose.Krudcutter is safe for surrounding plants and grass and works well without employing harsh chemicals or acids.
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