I bought moss/patio cleaner emailed HSD explained not done anything to my patio etc. Customer service kindly explained to me that to remove blackspot ect from my patio/block paving I need their black spot remover. they kindly sent me free of charge and delivered a 5LT bottle to try. must say my patio ect was very bad and needed two/three sprays to get it looking nice again. have a big drive and large patio so I have purchased 40 LTS and it's looking good. The warning does not use if windy/too hot/or if rain is forecast will send some images when all is done, before and after. very happy so far