The advantage of the carwash is that their containers are
much more manageable at 20 gallons. Such a place near
me regularly puts them out, with a felt-tip marking of "FREE".
They disappear within a day. And the contents are usually
water-soluble, so they can be washed out to get rid of the
foaming agents.
Also, they regularly have 10 gallon containers, and all the
containers have caps that are easily manageable.
Obviously, if your containers are in the sun much, it wouldn't
hurt to replace them before they get brittle and crack, and
it sure is nice for them to be free.

On Mar 7, 10:46*pm, Eric in North TX wrote:

Find a carwash and find out who suppliles them with soap & such. I
have a friend in the business, he is happy to give them away, they
build up so fast, if he doesn't give them away they make his place an
eye sore.