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Re: Filter Flow
>> If the pump uses an impeller, you should restrict
>> the output flow, not the input flow. Reducing the
>> input will destroy the pump.
> Then, how come cannister filters place the media on
> the intake side of the impeller assembly - isn't
> this effectively the same as reducing the input
> flow? I understand that this is done to give
> suction, rather than pressure, inside the
> cannister - making any leaks less of a trouble,
> but at the expense of the motor? What am I
> missing here?
I don't know, but I've been similarly confused with
small, magnetically driven submersible pumps. For
example, I ran a Cal Pumps Model #P140 for about two
years in my garden pond. The pump died when a
nocturnal visitor to the pond pulled the filter
assembly out of the water and the unit ran dry. That
pump's flow adjustment was on the intake side.
I now have a Rio Model #180 in the pond (with a much
more raccoon-resistant filter assembly). That pump's
flow adjustment is intended to be placed on the
outfall side, and the documentation specifically
states that restricting inflow voids the unit's
warranty.
Powerheads have similar mechanisms and are designed to
accept input from UGF's. Depending on gravel
composition and volume, that would create a
considerable restriction on intake.
Any pump/filter combination that 'pulls' water across
the media has its inflow restricted. Any combo that
'pushes' water across the media has its outflow
restricted. Some means of screening the water of
debris is necessary in almost all settings, so some
restriction must occur.
I believe that, with a few variations to avoid patent
infringement lawsuits, all these pumps use basically
the same hydraulic principles in their design. It'd
be nice if we knew for sure.
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