5-22
October 2012
replaced, but they use the greatest amount of water to flush particulates out of the
sand in the backwash process. Sorptive media filters use less water, but must be
replenished after every backwash, as the media is purged from the filter grid along
with the debris. Replenishment is accomplished by mixing new sorptive media with
water and pouring it into the skimmer closest to the pump. The pump then trans-
ports the sorptive media to the filter and deposits it onto the filter grid.
Cartridge units eliminate backwashing by using pleated filters made from a paper-
type material that can be reused or disposed. Instead of backwashing, disposable
cartridge filters are removed, discarded, and replaced with a new filter. Reusable
filters are rinsed with a spray hose or soaked in a cleaning solution before being
brushed or rinsed. While cartridge filtration is the most water-efficient, it is not usu-
ally a viable option for large commercial pools because the cartridge replacement
rate quickly becomes cost-prohibitive and labor-intensive.
52
Large commercial pools sometimes use a fourth filter type, industrial filters, which
are a specific type of sorptive media filter. These filters are more efficient than tra-
ditional sorptive media filters because they can recycle the sorptive media up to 30
times before it must be discarded and replaced. Unlike traditional sorptive media
filters, which pass water straight through the filter during backwashing, industrial fil-
ters recycle the water that is used to backwash the filter. As a result, the total volume
of water used during backwashing is reduced to only twice the volume of the filter.
53
The East Bay Municipal Utility District in Oakland, California, recommends using sorp-
tive media for commercial pools and cartridge filters for spas.
54
Table 5-3 provides an
overview of the water use associated with each filter type, as estimated by CUWCC.
55
These estimates show that, for smaller pools and spas, cartridge filters use less water
than sand, sorptive media, or industrial filters. For larger pools, industrial filters are
much more efficient.
Table 5-3. Filter CleaningWater Consumption Estimates by Pool and Filter Type
Pool Type
Pool
Volume
(
gallons)
Water Use (gallons per year)
Sand
Sorptive
Media
Cartridge Industrial
Spa
1,100
940
470
300
N/A*
Hotel
(
in-ground)
34,000
30,000
9,400
3,600
5,000
Public
(
in-ground)
150,000
170,000
42,000
N/A
9,000
Olympic
(
in-ground)
860,000
960,000
240,000
N/A
17,000
5.4
Commercial Pool and Spa Equipment
52
East Bay Municipal Utility District (EBMUD). 2008.
WaterSmart Guidebook—A Water-Use Efficiency Plan Review Guide for New Businesses
.
Page 171.
.
53
Koeller, John and H.W. (Bill) Hoffman & Associates, LLC,
op. cit.
,
Pages 18-19.
54
EBMUD,
op. cit.
,
Page 174.
55
Koeller, John and H.W. (Bill) Hoffman & Associates, LLC,
op. cit.
,
Page 35.
*
N/A: not applicable
