SURFACE STAINING
THE PROBLEM:
Dissolved metals and minerals are present in every
swimming pool. These dissolved solids find their way into
a pool water in a number of ways: Fill water from wells
or from city water lines can deposit dissolved minerals
into the pool. Galvanized pipes and bronze or copper
fittings in pool pumps and heaters are sources of iron, copper, and manganese. Foreign objects, from bobbie
pins to pine needles, leave behind trace metals and
minerals. Evaporation removes water from the pool, but
leaves minerals behind, gradually raising the pool
water's total dissolved solids level. Over time, these
dissolved solids will precipitate, or "fall
out" of the pool water, and settle into the suface
of the pool. The resulting rust orange, brown, grey,
and light
blue-green
stains are unsightly, and detract from the beauty of your
swimming pool.
THE OPTIONS:
Among the options available to the homeowner are the
following:
- Periodically draining and acid
washing
the pool surface.
- Mechanically removing minerals
before they have a chance to deposit on the
plaster. The type of filter required to remove
minerals and heavy metals is called a nanofilter. It will clean the
water to "bottled water purity" without
having to drain water from the pool. Once the
pool water has been cleaned with the filter, a
chelating agent can be used to maintain the water
in a "soft" condition.
- Chemical
treatments, which remove minerals before they have
a chance to settle on pool surfaces. These
chemicals are called chelating agents. Their name comes from
the Latin word for "lobster claw."
Chelating agents "pinch" dissolved
metals and minerals, holding them until they can
be strained out of the pool water by the
filtation system. Chelating agents are also known
as sequestering
agents.
THE BENEFITS AND
THE DRAWBACKS:
- Draining and acid
washing the pool will eliminate many stains, but
it also accelerates pool plaster disintegration.
Done by untrained or incompentent technicians,
acid washing can lead to irreparable damage, from
etching or pitting of the pool plaster to
cracking of the pool shell.
The cost and quality of acid washing vary
tremendously. Houston area pool companies
typically charge between $125 and $600 for an
acid wash! Since there is little regulation of
the pool repair industry, you can't always be
certain of the competence of the crew performing
the acid wash -- the less expensive companies may
actually provide the highest quality service!
Whatever the cost, you must pay the expense of
draining and refilling the pool, which typically
runs in the $100 range.
Acid washing removes stains by dissolving a thin
layer of pool plaster. The short-term result is
whiter, cleaner plaster, but the long term
effect-- rougher, more stain-susceptible plaster
-- makes the process very unappealing.
- Nanofiltration
costs $80 per day. Most pools require two or
three days of nanofiltration. The nanofilter
removes 300 to 400 parts per million of dissolved
solids per day, greatly reducing the possibililty
that metals or minerals will "fall out"
of the water.
The nanofilter is a portable unit, with its own
pump and plumbing. It must be set up on your pool
deck, making for an unattractive temporary
addition to your backyard. Since dissolved solids
are constantly building up in the pool water,
nanofiltration must be done every 6 to 8 months.
- There are a variety of chealting agents
on the market. Pelican Pool Service offers YR-17, a very effective stain prevention treatment.
Developed by a team of chemists and pool professionals in southern California,
one gallon of YR-17 should be added to the pool every 4
months, all year 'round. While YR-17 will not remove existing stains, it
is an outstanding means of preventing new stains from forming.
COSTS:
Whatever stain prevention treatment you choose,
there are costs invloved. For example:
One acid wash --
- $125 to $600 (with
accompanying plaster disintegration) + $100 water
refill costs = $225 to $700
1 year of
nanofiltration --
- About 4 days per
year, @ $100 per day = $400
1 year of YR-17 --
- 3 gallons @ $35
per gallon = $105
CONCLUSION:
Regular maintenance is the best prevention against
staining. Regular use of a chelating agent will prevent
stains, preserve the appearance of your pool, and save
the headaches and risks associated with nanofiltration
and acid washing.
Some surface discolorations are not stains at all, but
result from flaws in the pool plaster. For information on
calcium chloride spotting, crazing, spalling, and other
flaws, please see our plaster problems page. |
