Re: Pump Flow rates vs statements of flow rates

["S. Hieber" <shieber at yahoo_com>]

A little while ago, Jeff Ludwig did a post to lay down some
of the basics regarding pump flow rates.

I would  add that tubing friction is relatively imortant
after they have been in place for awhile and biofilm begins
to build up -- the effect on flow rate can be visually and
measurabley startling.

I would also add that curve charts are helpful if the
conditions for them are stated.  Eheim has a habit of using
the same pump on filters of different size and rating the
output higher on the larger filter even though it offers
more resistance -- pure jiggery pokery in my opinion.  So
you have to take statements about flow rates as being as no
better than the statement of test conditions.

For any maker of pumpos/filters, the flow rate is rarely
stated for a unit in place with any build up of material in
the media, which is acutally the most common condition for
filters in use.

Yet, calculating the rates, taking everything into account,
elbows, friction, gravity (least important on cansiter
filters where it's effects tend to concel out), is a tough
job.  

Calculus anyone?

Scott H.

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