WATER CHEMISTRY TERMS YOU SHOULD KNOW
Before jumping into the Spa Water Maintenance, here are some terms to help you.
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1. Parts per million, or ppm: This is a form of measurement used in most pool
or spa chemical readings. Best described as any one million like items of equal
size and make up, next to one unlike item , but of equal size. This would be
one part per million.
2. Average size spa: What is it? The national spa and pool institute (NSPI)
states; 350 to 400 U.S. gallons is average. As a general rule, chemical dosages
are the same for any spa between 100 and 500 U.S. gallons. Spas over 500
U.S. gallons the dosage would be double. Under 100 U.S. gallons would be
on a case by case basis.
3. Total Alkalinity: This is a measurement of the ability of the water to resist
changes in pH. Put another way, it is the water’s ability to maintain proper
pH. Total alkalinity is measured in parts per million from 0 to 400 plus, with
80 to 150 ppm being the best range for spas. With low alkalinity, the pH will
flip, or change back and forth, and be hard to control. With high alkalinity it
becomes extremely difficult to change the pH.
4. pH or potential hydrogen: This is a measurement of the active acidity in the
water, or it is the measurement of the concentration of active hydrogen ions
in the water. The greater the concentration of active hydrogen ions, the
lower the pH. pH is not measured in parts per million, but on a scale from
0 to 14, with 7 being the neutral. In spas when ever possible, a measurement
between 7.2 and 7.8 is best. Whenever possible, it should be between 7.4
and 7.6. With low pH, the results can be corroded metals, etched and stained
plaster, stained fiberglass or acrylic, eye / skin irritation, rapid chlorine or bro-
mine loss, and total alkalinity destruction. With high pH, the results can be
cloudy water, eye / skin irritation, scale formation and poor chlorine or bro-
mine efficiency.
5. Shocking: This is when you add either extra chlorine (superchlorinate)
by raising the chlorine level above 8 ppm, or add a non-chlorine shock
(potassium monoperoxysulfate or potassium monopersulfate) to burn off the
chloramines or bromamines. A non-chlorine shock acts by releasing oxygen
in the water, which serves the same function as chlorine. The advantage to
using non-chlorine shock, is you can enter the water within 15 minutes after
shocking. Using chlorine, you must wait until the total chlorine reading is
below 5 ppm. One thing to remember, a non-chlorine shock will not kill
bacteria or disinfect.
6. Sequestering: This can be defined as the ability to form a chemical
complex which remains in solution, despite the presence of a precipitating
agent (i.e. calcium and metals). Common names for sequestering chemicals
are; minquest, stain and scale control, metal-x, spa defender, spa metal
gone, (etc.).
