# Re: filter flow rates(yet again)

```On Wed, 29 Dec 1999, Roger S. Miller wrote:

snip<There's no reason to throw an arbitrary coefficient into some formula to
get that qualitative conclusion.>snip

While the coefficient may well seem arbitrary, I assure you it is real.  Let
me explain how the proof works.(Now having gone to the university and bought
a workbook with the experiment in it). First you take a given volume of
water, say 55 gallons (aquarium size amount of water). You add something (it
doesn't matter what), but for our experiment let's say phosphate.  You add
phosphate until the it is 10 PPM. Now you run the entire volume of water the
a filter that is filtering for phosphates (doesn't matter what kind of filter
as long as it is the same as you will be using later in your aquarium). When
the water is filtered one time, you measure it for phosphates.  Let's assume
they now read 0.5. You now know that when all the water has pass through the
filter once(carring with it the phosphate molecules) that the reading will be
0.5. You know this because you just did it.  Now, set up your aquarium. Now
is how you prove the formula works. Assume we have a filter the filter at a
rate of 400 gph. If measuring it your way worked, then after 8-9 minutes the
reading when we measured it would be 0.5. In reality, it would take closer to
105 minutes before we reached that reading.

snip<So what is the point to using some arbitrarily selected value?>snip

Being one of many that did this experiment, as much as you may disagree, the
numbers in the formula do work and give you a more accurate number by which
to determine how fast 'all' your water makes through the filter.

snip<There's no reason to throw an arbitrary coefficient into some formula to
get that qualitative conclusion.>snip

The reason is so you can figure out how long it will take your water to reach
a given water quality based on the rate of filtration.  Not trying to start
an argument, just trying to explain.  Happy new year all!

James Watford
Columbia,S.C.
```