Am not sure of the mix % of black wash but I understand it's about 2-5% when u buy it, if u then dilute it to 1/10 it's not guna be very strong mix.
Hypo wen bought in the barrell is at 15% strength so mixing this 1/10 would give u approx same mix as black wash as it comes.
With hypo as we buy it, is not guna pass any on site h&s but black wash does.
If I am pressure washing and using hypo I will dilute it 1/3 and use it in areas required