Cleaning exterior flagstone

[alazo1]

These are walkways. Should I do it with just the pressure wash gun?. There's a lot of mold and wonder if the pressure would be enough. I don't want to contain the water but customer wants containment if I use chemicals. The truck has up to 1500 psi.

What would you do?

Albert

 

[Mikey P]

99% of the time pressure alone works fine.