Pool Chemicals for Beginners

You can start without filling a whole shelf. This short list handles nearly everything a home pool asks for:

• Test strips when you want a fast answer, or a kit that uses drops
• 12.5% liquid chlorine; if you have a salt cell, follow its manufacturer's salt target
• Muriatic acid for bringing pH down
• Soda ash for bringing pH up
• Baking soda, which lifts alkalinity
• Stabilizer (cyanuric acid) if your pool sees sun
• Calcium chloride when a test shows calcium hardness below 200 ppm

Your results are given in parts per million (ppm). That's simply how much of a chemical is dissolved in the water, and it's what your strip or kit reports.

Free chlorine means the chlorine that's still active and cleaning your water. How much you need goes hand in hand with your stabilizer reading, so read the two together.

Stabilizer is cyanuric acid (CYA for short), and its job is shielding chlorine from sunlight. Nothing breaks it down or filters it out, so the only fix for too much is draining some water and refilling.

Total alkalinity measures how well your water holds pH steady. When it's in range, your pH stops bouncing around.

Each dose depends on how much water you're treating, counted in US gallons. Here are common sizes, assuming the water averages 4.5 feet deep:

A sloped floor means the average depth sits halfway between the shallow and deep ends. Round and oval pools hold less, so for those shapes, or any pool not listed here, the site's pool volume calculator works out your gallons and remembers them for every dose calculator.

Most strip manufacturers, AquaChek included, give roughly the same directions. Follow them closely, because the colours shift fast.

1. 1. Lower the strip to roughly elbow depth, about 18 inches under, and leave it there a second or two.
2. 2. Pull it back out, keeping it level, and resist the urge to flick off the extra water.
3. 3. Within about 15 seconds, hold each pad against the chart printed on the bottle, using daylight.
4. 4. Check the pads in the order printed on the bottle.

The usual pads measure chlorine in both forms, free and total, along with pH and total alkalinity. That total counts both the free chlorine and the chlorine that's already done its job. A few strips add pads for stabilizer and calcium hardness.

Cap the bottle and keep it dry between uses. Expired strips give you bad numbers.

These figures assume a 10,000-gallon pool. Double them for 20,000 gallons, and cut them in half for 5,000. For any other size, the site's pool chemical calculator gives the dose of each product for the gallons saved in your browser.

Keep the pump running whenever you add anything, and pour near a return jet so the current spreads the product through the pool. Never combine products in the water; let each one mix in on its own.

Acid goes into water, never the reverse. And keep acid away from chlorine entirely. Once you've added acid or soda ash, give it 30 minutes, then test pH again to see where things landed.

With liquid chlorine at normal levels, wait about 30 minutes before getting back in. After a shock, test first. Go ahead and swim once free chlorine has returned to a level that suits your stabilizer reading and pH has settled in the 7.2 to 7.8 zone. The CDC Model Aquatic Health Code caps free chlorine at 10 ppm for swimmers.

If stabilizer is too high, the only fix is replacing some water. For example, dropping from a reading of 100 down to 50 calls for swapping out roughly half of what's in the pool. The site's calculator can work out other cases for you.