That will fly off with HDT&Grout Cleaner and some Honing Powder with a Mono Rotary and a Brush and make a lot less mess than a PW
How will that method deal with the moss & weeds betreen the joints?
I buy hypo from a farm supply shop, farmers use it to disinfect milking machines( I think) it cost £11 for 20lts
I've tried to use a rotory to clean outside areas it was very difficult and the result was not good I found the brush could'nt ride across the unevenness of the surface, although I am going to try it again on concrete with a hypo mix as I think it could work well on a relatively smooth surface like concrete