"BenignVanilla" wrote:

Is there a sizing algorithm for settlement tanks?

Sure, keep the water in the tank long enough for stuff to settle!

To not be smart, it depends on the water flow.

I was thinking of burying one or two 5 gallon buckets for the settlement
tanks. Would be cheap and easy.

If you connect a 30 gpm (1800gph) pump, that would allow less than 10
seconds settling time, which is to say none.

Would this be big enough to allow for some
SOME settling before the pipes dump into the filter? My intent is to have
the sediment dropped into/used by the veggie filter, but I don't want to
connect the drains directly to my pump for fear of clogging.

Go google and take a look at some of the designs on the web.