How many PSI may be appropriate for cleaning a rec

I clean with a Loricraft but still find that there is some grime that doesnt come out on occassion. This will usually dissapear after multiple playings and cleanings but what about low pressure washing? Is there an appropriate PSI level? Has anyone tried this?
I have always wanted a 'waterpic setup for such stuff. Since they can cut 2" thick steel with just water pressure jets, I guess a limit is there before damage would occur. I don't think a city water pressure, even with special nozzles could reach that though.