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Old 03-02-2003, 06:25 PM
Bonnie Espenshade
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Default Settlement Tanks

BenignVanilla wrote:
"John Hines" wrote in message

"BenignVanilla" wrote:

Is there a sizing algorithm for settlement tanks?

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

*laugh* OK, so what's that time period?

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


I did some quick math, assuming a 2000 gallon pond, and an 1800GPH pump. It
would take the pump 67 minutes to circulate the water in the pond. With a
200 gallon settlement tank, the water would have only 7 minutes to settle in
the tank. I realize this does not take into consideration of the volume in
the pipes. I am just trying to get close here. So is 7 minutes enough? I am
guessing not. A 500 gallon settlement tank would provide about 17 minutes of
settle time. Still seems a bit low.

The reason I ask is that, it seems like a lot of work and doing to get a
settlement tank going. Since I plan to have a shallow veggie filter,
cleaning it should not be a big deal. I am wondering if I should just forget
the settlement tank, and let the sediment come into the veggie filter, which
could easily be drained, cleaned and refilled.


When I built my first veggie filter it was suggested that
the turnover rate be once every four hours, so that it
would have enough time for the plants to absorb the nutrients.
The argument ensued here on rec.ponds - whether time in the
filter or amount of water passing through the filter where
more important. It was never really settled - as usual we
each came to our own conclusion because our ponds are all
To slow down the waters passage through the settling tank
several of us have added window screening. This works great
in allowing the muck to settle and the window screening is
very easily cleaned with a hose.