Using the Rainbow 2n1 Swimming Pool Test Kit

Using the PS200 OTO/phenol red Swimming Pool Test Kit

The 2n1 kit is a quick, easy, reliable, inexpensive - but not too accurate - swimming pool test kit that should be used for daily testing. It's the kit you should carry out to the pool. And, it's the kit you should replace at the start of next year.

There are many similar test kits available on the market; some are probably just as good, but some are distinctly inferior. I don't know of one that is better.

It is IMPORTANT to understand what the 2n1 kit is for, and how it should be used! Taking the time to understand will help you avoid MANY swimming pool problems.

CONTENTS

(2) bottles, one containing OTO, one containing phenol red. Don't drink either one, or squirt it in your eyes.
A 'test block' containing a test cell for pH and one for chlorine/bromine.
A white background card (hold the card against the test block when reading the kit).

KEY POINTS TO REMEMBER

The 2n1 uses two reagents (test chemicals): OTO (orthotolidine) and phenol red.
OTO turns from clear to yellow in the presence of chlorine, bromine, or other oxidizers.
The 2n1 is labeled for chlorine . . . but you can use it for bromine. If you test a pool with 2.25 ppm of bromine, the 2n1 will indicate you have 1 ppm of chlorine. In fact, on a pool treated with bromine, you can always multiply the indicated reading by 2.25 (or just 2) to determine the bromine reading. Or, you can forget about it, and simply run a bromine pool and maintain apparent chlorine levels between 1 and 3 ppm, and you'll be fine.
Non-chlorine or oxy-shocks - which are NOT sanitizers OR algaecides - will turn OTO yellow. If you use these in your pool (which I don't recommend), you'll need to check the pool with a DPD kit (like the Taylor K2006) to verify that chlorine is present.
The darker the yellow color, the more chlorine (or oxidizer) is present. Most people cannot reliably distinguish more than 5 shades of OTO: clear, light yellow, yellow, dark yellow, and brownish yellow. Essentially, these five shades correspond to "WAY TOO LOW", "LOW", "OK", "HIGH" and "WAY TOO HIGH!". Some people can distinguish between "OK, but LOW" and "OK but HIGH", but not everyone can.
The 2n1 identifies "IDEAL" as being between 1.0 and 1.5 ppm of chlorine and between 7.4 and 7.6 on pH. Following this recommendation usually won't hurt, but as you become more experienced, you may find other levels are better. Well run home pools may have chlorine levels that are between 0.5 and 5.0 ppm and between pH levels 7.2 and 8.0.
The brownish yellow color only begins to appear when chlorine levels are 20 ppm or higher. This is too high for people, swimsuits, and hair. It's especially too high for babies, but unfortunately, kiddie pools are often this high! (Or else, too low.)
Don't swim in pools that test "NONE" or "WAY TOO HIGH"!
Phenol red changes color, from yellow to purple, as the pH changes.
Phenol red is affected by high chlorine: if OTO indicates the chlorine is "HIGH" you may not get an accurate pH test result. If the OTO turns brownish yellow, the phenol red test is useless, till the chlorine level comes down.
The exact number of drops used is not critical, using 4 or 6 drops of OTO or phenol red, instead of 5, will not greatly change the results.
Rinsing the test cells out is important. Rinse the kit's test cells with pool water before using it.

Other info about the PS200