Page 173 - WaterSense at Work

October 2012
Commercial Pool and Spa Equipment
Mineral Buildup Control
Water in pools and spas experiences a continual buildup of dissolved solids in the
form of mineral salts and treatment chemicals. This buildup must be treated or re-
moved to prevent scale buildup or corrosion of pool surfaces and equipment. Proper
pool maintenance and water quality control are essential for extending the useful life
of the water. Water quality control significantly saves water by reducing the number
of times the pool must be completely drained and refilled, the number of filter back-
washes needed, and the potential for leaks due to corrosion or other factors.
All pools require water to be exchanged periodically in order to control the buildup of
solids and other contaminants. This water exchange can be either partial or full and
can be controlled manually or through an automated process. When draining the pool
manually, the pool operator will simply pump pool water directly to the drain at some
predetermined point in time. The automated approach utilizes conductivity control-
lers, which drain a portion of the pool water once a predetermined concentration of
total dissolved solids is reached. Conductivity controllers save water by limiting ex-
changes to when they are necessary. The amount of water lost in the exchange process
will depend upon pool volume, dissolved solids concentration in the make-up water,
type and amount of treatment chemicals added, and the local evaporation rate.
Reverse osmosis systems, which operate independently frompool filters, are also utilized
to prolong the useful life of pool water. During reverse osmosis filtration, pool water is
passed through a membrane filter, which selectively excludes dissolvedminerals and sus-
pended particles frompassing through the filter. Water is able to permeate through the
barrier and is recovered and returned to the pool. The dissolvedminerals and suspended
particles that are trapped behind the membrane filter are then discharged to sanitary
sewer lines as reject water. Recovering the pool water in this manner eliminates the need
to dump and refill the pool. While reverse osmosis systems are effective at filteringminer-
als, they waste a large amount of water in the treatment process. A large facility should
consider the amount of reject water that would be produced if utilizing this equipment.
Leaks and Splashing
Water is lost in pools and spas from leaks and splash-
ing throughout their useful life. Common leak locations
include pump seals, pipe joints, piping in filtration system
suction or return lines, pool liners, and along pool edges.
A leak may be present if a pool is losing more than two
inches of water per week. Air bubbles in either the pump
strainer basket or water return line can also indicate the
presence of a leak.
Water is also lost during pool use from
splashing and drag-outs as swimmers exit. Water loss from
drag-outs can be mitigated by the use of gutter and grate
systems installed along the edge of the pool. Although
leaks and splashing contribute to water loss, it is difficult to
quantify the frequency and extent to which they can occur.
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