On Sat, 17 Jul 2010 11:19:31 -0700 (PDT), gpsman wrote:
I suspect the "standard" method is considered "close enough" in the
pool industry.

A pool professional told me almost everyone underreports their pool volume
because they forgot to take into account the appreciable volume of water in
the plumbing and filters and solar equipment.

He said the rule of thumb for the amount of water locked up in all that
plumbing is equal to the last two inches. So, for example, if you have the
standard 60x15 foot rectangular pool, your last two inches are about 1,000
gallons.

Whatever calculation you come up with, add 1,000 gallons for the water in
the plumbing, assuming that pool pro knew his stuff.