yes there are a few
but
most RV parks do not use septic tanks
they are hooked to city sewer
so
just about anything you wish to use is ok
but
as we remember
in most cases we are cleaning plastic
an abrasive may stain and or scratch surface
Mountainman
ps
even in our septic tank up top the mountain here
one can not help but to get some
Ajax down the drain at times for a real cleaning
such things do kill needed septic tank bacteria
but
got to do what you have to do
try to go light