Its hard to find the SH you guys use here in my city, probably kind of impossible, if i am not mistaken it has like a 10%-12% of concentration . I have read that you can use domestic bleach (the one you use for your house). I found a recipie of a house wash mix that in a bucket of 5 gallons you add:
5 liters of house bleach
300-400 ml of surfuctant, which can be soap for dishes
And the rest of water
And you apply it with the black nozzle , let it rest for 5-10 minutes and then pressure wash
What do you think?