Ranges[] acceptable and ideal ranges will vary
       depending on pool or spa type, sanitizer, geography, local
       laws, etc. Ranges are in ppm (parts per million) except pH. 

- pH [7.2-7.8]: Acid/base of water. Perform a/b drop count
                test for greater accuracy

- Alkalinity [80-140]: Stabilizes the pH. 

- Calcium [100-400]: Water hardness. Used to slow the waters
                     ability to dissolve plaster. Probably not
                     needed in non-plaster pools.  

- Cyanuric Acid [30-100]: Increases longevity of chlorine
                          by shielding it from the sun

- Chlorine [1-5]: Free and total. Normal and shock amounts
       
- Bromine [2-6]:

- Biguanide [30-50]: Alternate chemical water sanitizer.
                     Brands name(Baquacil and SoftSwim). 
                     Not compatabile with chlorine or bromine.
                     
- Iron   [0-.2]: Can stain the pool surface

- Copper [0-.2]: Can stain the pool surface

- TDS [0 - 2500]: Total dissolved solids

PoolSoft will give you the exact dosages of chemicals based
on your test results and the volume of water. You'll never
again have to look in tables or perform any chemical dosage 
calculations.

Depending on the size and usage this could save you
hundreds of dollars each year in chemicals and maintain
the water clean, safe and crystal clear.

Following are most of the chemcials used to balance
and sanitize the water in pools, spas and hot tubs.

pH:
   Sodium carbonate (soda ash) increases pH
   Sodium Bisulfate (dry acid) lowers pH
   Hydrochloric acid (Muriatic acid) lowers pH

Alkalinity:
   sodium bicarbonate (baking soda) inceases alkalinity
   Sodium Bisulfate (dry acid) lowers 
   Hydrochloric acid (Muriatic acid) lowers

Calcium:
   calcium chloride increases hardness
   to lower you may need to dilute water

Cyanuric Acid: for use with chlorine only
   cyanuric acid increases
   to lower you may need to dilute water

Chlorine: [effect on pH assuming 7.2-7-8 range] [% of available chlorine]
   calcium hypochlorite [raises] [65%]
   sodium hypochlorite - bleach   [raises] [5-15%]
   lithium hypochlorite [raises] [35%]
   Dichlor [lowers] [56-62%]
   Trichlor [lowers] [90%]
   chlorine gas [lowers] [100%]

Bromine:
   bromo-chloro tabs [lowers]
   2-part; sodium bromine and peroxymonosulfate [lowers]

Metals: Iron or copper
   use a chleating or sequestering compound

TDS:
    Just about any chemicals will increase.
    Dilute water to decrease.

Algaecides:
   will help to control and kill algae. Some are
   specially formulated for different types.

Clarifiers:
    can help to clear cloudy water by coagulating
    small particles, so they can be filtered. 

Shocking or super chlorinating:
   - the process of oxidizing contaminates to clarify
     the water and to kill large quantities of algae
   - a large dosage of chlorine 5+ ppm
   - a non-chlorine oxidizer (persulfates)
   - hydrogen peroxide, for biguanide systems

Biguanide: Brand names, Baquacil and Soft Swim
   - Alternate sanitizer, not compatable with chlorine or bromine.

Fast dissolving chemicals generally are spread around the pool. 
Slow dissolving chemicals are either pre-dissolved(add chemical
to the water), added to the skimmer (where they dissolve in the
filter before entering the pool) or put in a return line feeder (tri-tabs).
   
If a large adjustment is needed (especially lowering alkalinity)
break the dosage up over several intervals (hours).
   
Most chemicals have an effect on pH. Check it frequently if 
large adjustments are make. Cyanuric acid, as it's name implies
will reduce the pH.
The order in which chemicals are added is also important.
It's always a good idea to read the manufacturers labels. 

DPD - has 2 tests one for free and one for total chlorine.
OTO - is one test for total chlorine.

If the water is properly sanitized free and total will be the same.
If comtaminates are present total will be higher.
Combined  = Total - Free
OTO alone therefore can't test for contaminates. DPD does.
 
However DPD total tests has 2 draw backs. You can get a false
high reading if persulfate oxidizers have been used (some kits 
provide any additional tests to eliminate certain persulfates) and it
will bleach out (color will fade) at relatively low levels (10ppm). If you
have too much chlorine you may thing you have none. Both errors
will result in you adding more chlorine, when that's the last thing you
want. 
OTO on the other hand will not beach out even at 50,000ppm
(5% bleach). The perfect world would probably be to test free with
DPD and total with OTO. The problem is you would have to cross
check two different colors.

Note: DPD tab will not bleach out instantly. If tab turns color
then bleaches out as it dissolves, the chlorine is probably to
high. Dilute the water sample and retest.  

pH and Alkalinity are closely related. If you adjust one
you'll adjust the other. Alkalinty acts as a buffer for the
pH. Helps to stabilize the pH so that it's not continually
going up or down.
Adjust the alkalinity first, then the pH.

Many references suggest different alkalinity, pH and calcium
ranges based on the type of pool and the most frequently
used sanitizer. In general lower alkalinity and higher calcium
for plaster surface pools. Lower alkalinity (low end of range)
when using hypochlorites, high end of range when using 
tri-chlor or gas chlorine. 
pH ranges from 0-14. 7 is sterile water. Below 7 is acidic
above 7 is alkaline or basic.

References and general chemistry says that chlorine's
ability to destroy bacteria is greatly effect by the pH.
A pH of 7.2  has 3 times the destructive power of 8.0.

Bromine is also effected but not as dramatically.

How often each test should be performed varies. Some factors would be: 

1) Bather usage.
   Heavy usage will require more chlorine/sanitizer.

2) Weather, lots of rain, etc. very sunny.
   Rain will effect pH and chlorine.
   Strong sun will destroy the chlorine - see cyanuric acid.

3) Type of chlorine being used.
   Bleach - raises the pH
   Cal-hypo - raises the pH and Calcium hardness
   Di and Tri chlor - lowers pH and increases cyanuric acid.

4) Tap, fill water. Test the fill water, then you will have
   a good idea of the adjustments you will need to make to
   the pool.  

Adjust the frequency based on how much change there is from
last test.

pH  -      daily, more frequently if heavy usage
Chlorine - daily, more frequently if heavy usage

Alkalinity - weekly

Calcium - monthly
Cyanuric - monthly

Iron - if there is none in the pool or fill water, you should be ok.

Copper - if there is none in the pool or fill water, you should be ok.
         Some algaecides contain copper.

The lists of chemicals that can be used is extensive.
However, in most cases a few chemcials is all you
will needed, especially if the pool is properly maintained.

Copyright 1992-2001 PoolSoft. All rights reserved.
Tim Sullivan,35 Brewster Dr.,  Gales Ferry, CT 06335,  USA
860-464-2217