This may be a silly question if they are using only 1% hypo to clean roofs and it's getting all the crap staining and lichen off the tiles surely using 14 or 15% hypo on slabs is major overkill or the 1% mix can't be cleaning the roofs that well if you look close up.
It is working!!! It is all about dwell times and multiple applications if required. The issue here is everyone wants instant results where as dwell times and if necessary a second application are a better route than powerful chemicals that destroy everything they come into contact with. However, lots of people will disagree. This is why Algoclear is not popular because it needs a little time!!!
Analogy: If my wife burns my lasagne in the oven, she adopts "Lets see how hard I can work method" and then proceeds to spend 1/2 hour+ attacking the oven proof dish with an arsenal of pan scourers, magic sponges, Microfibre cloths and every cleaning chemical and spray available to mankind. I just laugh because I am sick of trying to educate her.
I achieve the same if not better results with the "My have a cup of tea method" I drop the dish in warm soapy water overnight, make a cup of tea and the next morning give it a quick wipe with a microfibre cloth
We both achieved the same result and got the dish clean! You decide which method was best???
