Pool Chemistry Basics: The ABCs of Water Balance

Pool chemistry sounds complicated, but it comes down to five things: chlorine, pH, alkalinity, stabilizer, and calcium. Get these right, and your pool stays crystal clear. Get them wrong, and you're fighting algae, scaling, or corroded equipment. Here's the plain-English guide to what each one does, what level it should be, and how to fix it — written by CPO certified technicians who test and balance pools every day in the Texas heat.

The Big Five: Your Pool Chemistry Cheat Sheet

Chlorine (FC): Your Pool's Immune System

Chlorine is what kills bacteria, viruses, and algae. Without enough of it, your pool will turn green — guaranteed. The key thing most pool owners don't know is that your FC target depends on your CYA level, not a fixed number.

The rule: your minimum FC should be 7.5% of your CYA level. So if your CYA is 40, your minimum FC is 3 ppm. If your CYA is 60, your minimum FC is 4.5 ppm.

In Texas, the sun destroys chlorine fast. Without stabilizer (CYA), you can lose all your chlorine in a single afternoon. But too much CYA means you need impractical amounts of chlorine to keep the pool safe. That's why we recommend keeping CYA between 30-50 ppm.

Types of Chlorine

• Liquid chlorine (bleach) — Best for daily/weekly dosing. Doesn't add CYA or calcium. Our preferred method.
• Dichlor (granular) — Adds CYA with every dose. Fine for occasional use, bad for long-term because CYA builds up.
• Trichlor (pucks/tabs) — Adds CYA continuously. Convenient but CYA climbs over the season. Common problem in Texas pools.
• Cal-hypo (granular shock) — Adds calcium. Fine occasionally, but calcium builds up over time.

Our recommendation: Use liquid chlorine for regular dosing and trichlor tabs in a floater for convenience, but monitor CYA closely. When CYA hits 50, switch to liquid only until it comes back down.

pH: The Most Important Number

pH measures how acidic or basic your water is, on a scale of 0-14. Your pool should be between 7.2 and 7.8 — slightly basic, close to your eyes' natural pH.

pH too low (below 7.2): Water becomes corrosive. It eats at plaster, metal fittings, and pool equipment. Swimmers complain of burning eyes and skin irritation. Chlorine becomes less effective.

pH too high (above 7.8): Water becomes scaling. Calcium drops out of solution and forms scale on your tile, equipment, and inside your heater. Chlorine becomes significantly less effective — at pH 8.0, chlorine is only about 20% as active as at pH 7.5.

How to Fix pH

• pH too low: Add soda ash (sodium carbonate) or borax. Soda ash raises both pH and TA. Borax raises pH without affecting TA much.
• pH too high: Add muriatic acid (hydrochloric acid) or dry acid (sodium bisulfate). Muriatic is cheaper and more effective but needs careful handling. Always add acid to water, never water to acid.

Pro tip: Always adjust TA first, then pH. TA acts as a buffer for pH — if TA is out of range, pH will keep bouncing.

Total Alkalinity (TA): pH's Bodyguard

Total alkalinity is the buffer that keeps pH stable. Without it, your pH will swing wildly every time it rains, someone swims, or you add chemicals. Think of TA as pH's bodyguard — it prevents pH from moving until you want it to.

Ideal range: 80-120 ppm. If you have a saltwater pool or are in an area with high CYA, aim for the lower end (70-80 ppm) to give pH room to move.

How to Fix TA

• TA too low: Add baking soda (sodium bicarbonate). It raises TA without raising pH much. Use 1.5 lbs per 10,000 gallons to raise TA by 10 ppm.
• TA too high: Add muriatic acid. This lowers both TA and pH. Then aerate the pool (run the jets pointing up) to bring pH back up without raising TA.

Cyanuric Acid (CYA): Chlorine's Sunscreen

CYA is a stabilizer that protects chlorine from UV destruction. Without it, the Texas sun can destroy 90% of your free chlorine in just a few hours. But too much CYA is actually worse than too little — it makes your chlorine less effective.

Ideal range: 30-50 ppm. Above 60 ppm and you start needing significantly more chlorine to keep the pool sanitized. Above 80 ppm, it becomes very difficult to maintain water quality without draining water.

CYA only goes up — it doesn't evaporate or break down. The only way to lower it is to drain and refill some of your pool water. This is why we recommend liquid chlorine for regular dosing instead of relying solely on trichlor tabs.

Calcium Hardness (CH): Protect Your Plaster

Calcium hardness measures how much dissolved calcium is in your water. Too low and the water becomes corrosive, pulling calcium from your plaster and grout. Too high and the calcium precipitates out, forming scale on your tile, inside your pipes, and on your heater elements.

Ideal range: 200-400 ppm for plaster pools, 150-250 for vinyl or fiberglass.

In the DFW area, our fill water tends to be moderate in calcium (150-250 ppm). If you're on well water, it can be much higher. The key is testing regularly and adjusting before problems start.

How to Fix CH

• CH too low: Add calcium chloride (not calcium chloride dihydrate — different product). Raises CH without affecting other levels much.
• CH too high: Partial drain and refill with lower-calcium water. There's no chemical that lowers CH — you have to dilute it.

The Order of Operations

When you're balancing a pool, the order matters. Here's the correct sequence:

1. Test everything — get a full read on FC, CC, pH, TA, CH, and CYA
2. Adjust TA first — it's the foundation for pH stability
3. Adjust pH — now that TA is stable, pH will hold
4. Add chlorine — only after pH is in range (chlorine is 3x more effective at 7.5 than at 8.0)
5. Adjust CH — this one can wait, it changes slowly
6. Check CYA — if over 50, plan a partial drain

Wait times between adding chemicals: 10-15 minutes between most additions, 30 minutes if you're adding acid then chlorine. Always add chemicals to water, never the other way around.

Texas Pool Chemistry Challenges

Pool chemistry in Texas is different from pool chemistry in Minnesota. Here's what we deal with:

• Extreme heat — 100°F days mean chlorine burns off fast. You need adequate CYA and consistent dosing.
• Intense UV — Texas sun destroys unstabilized chlorine in hours. CYA is essential.
• Long season — Our pool season runs March through November. That's 9 months of chemistry to manage.
• High evaporation — Water evaporates, concentrating chemicals. Regular top-offs and testing are critical.
• Hard fill water — DFW water can be hard, meaning CH and TA start high from the tap.

This is why CPO certification matters. Our technicians test and balance chemistry every week, adjusting for Texas conditions. If you're managing your own pool, test at least twice a week during summer and adjust accordingly.

Weekly Pool Chemistry Schedule

Or skip the chemistry class and let us handle it. Our weekly pool service includes all chemicals, testing, and balancing for $180/month. Get a free quote or call 682-399-2593.