Lots of cleaning products (soaps, degreasers, detergents, etc) are made
for power washers, but many, most or all of them state that they should
only be used with *downstream* injectors or pickup hoses - not
*upstream* pickup tubes where they will pass through the high pressure
pump itself.

Some washers mention to not use cleaning products that don't harm
certain types of pressure hoses (I forget the exact term they mention -
somthing like "N-Buta") and I've also read that citrus-based products
are safe (but it's hard to know if a given product is infact
citrus-based).

So I'm wondering if there is any additional info about just what can and
can't be used for a chemical cleaning product for down-stream pickup in
a power washer.