The bead filters are just sand filters with the flow reversed, using
polyethylene beads. I think that some of the manufacturers actually are
able to buy a backwards control valve, but some just take the plumbing apart
on the inside, sending the current down pipe from the bottom to the top, and
vice versa. The bead cake will sometimes glue itself together with the
biofilm, so the better filters have installed a jacuzzi blower and mounted
it on the intake piping so that during the backwash, the blower sends a lot
of air up under the beads breaking the bead pack. Look at some of the bead
filter manufacturer's sites and they show the internal plumbing and the
mounting of the blower. See
http://www.pondtech.net/PDF%27s/CHAL...N%20MANUAL.pdf and
http://www.sacramentokoi.com/comparison.htm

--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html
"Trevor" wrote in message
news
On Wed, 05 May 2004 00:51:00 +0000, RichToyBox wrote:

The biofilm is stubborn to wash off, and you don't want it to
be washed off. Therefore sand is a poor filter material. Find a
material
that is smooth and will barely sink to make backwashing easier and the
filter run better. The bead filters are sand filters that have the water
run through in an up flow method with floating plastic beads, but there
are plastic bead media that are heavy enough to settle, and these should
be used in the standard downflow mode of a sand filter. The beads
should
all be the same size to accommodate water flow without clogging.


RTB

Is that the only difference between a swimming pool sand filter and a
pond bead filter. Is there an easy way to convert a normal pool filter to
have the water flow up? Would it be a simple enough diy job? What do you
think of the efficiency of a down flow (pool) filter when filled with a
more appropriate media than sand?

Trev