Every swimming pool runs on six chemistry parameters working in concert: free chlorine, pH, total alkalinity, calcium hardness, cyanuric acid (CYA), and total dissolved solids (TDS). Keeping each one inside its target range is what separates a sparkling, safe pool from one that scales, corrodes, turns green, or stings your eyes. After 40 years of pool water chemistry consultations across our 8 Los Angeles-area stores, we at Discount Pool Mart can say with confidence that Southern California's notoriously hard tap water makes mastering these six numbers more pressing here than almost anywhere else in the country.
This pool water chemistry guide walks you through every parameter, explains how they interact, flags the mistakes we see most often, and gives you a clear testing schedule built around LA's year-round swimming season.
Unbalanced Water Does More Than Look Bad
Pool water balance protects swimmers, preserves your surfaces and equipment, and keeps sanitizer working the way it should. When chemistry drifts, problems stack up fast.
A pool with poor water balance sends clear distress signals:
- Scaling and white deposits on tile, heaters, and salt cells when calcium hardness and pH run high.
- Green or cloudy water when free chlorine levels drop too low or CYA climbs too high.
- Skin and eye irritation from chloramines (combined chlorine) or pH that strays from neutral.
- Corroded ladders, pump seals, and heat exchangers when low alkalinity or low calcium turns the water aggressive.
- Staining from metals that dissolve more readily in acidic, unbalanced water.
LA's Hard Water Raises the Stakes
Los Angeles receives its water from the Metropolitan Water District of Southern California, the Colorado River Aqueduct, and local groundwater. All three sources deliver water loaded with calcium and minerals. According to the LADWP 2023 Water Quality Report, LA tap water can arrive with calcium hardness above 200 ppm and TDS well over 300 ppm - before it ever touches your pool.
Pair that mineral-heavy fill water with year-round sunshine and minimal rainfall, and your pool concentrates dissolved solids faster and burns through chlorine quicker than pools in cooler, wetter climates. In our 8 stores, the single most common walk-in complaint is stubborn scaling. The root cause is almost always the same: LA's hard water pushing calcium, pH, and TDS out of range at the same time.
The Six Pool Chemistry Parameters Every Owner Should Know
Here is a quick-reference table, followed by a closer look at each parameter in this pool chemistry guide.
| Parameter | Ideal Range | What It Does | Too Low | Too High |
|---|---|---|---|---|
| Free Chlorine (FC) | 2-4 ppm | Kills bacteria and algae | Algae growth, unsafe water | Skin and eye irritation |
| pH | 7.4-7.6 | Controls chlorine strength and surface safety | Corrosion, eye sting | Scaling, weak chlorine |
| Total Alkalinity (TA) | 80-120 ppm | Buffers pH from swinging | pH bounces wildly | pH drifts high, cloudy water |
| Calcium Hardness (CH) | 200-400 ppm | Protects plaster and equipment | Etching, corrosion | Scale buildup |
| Cyanuric Acid (CYA) | 30-50 ppm | Shields chlorine from UV | Chlorine burns off in hours | Chlorine lock |
| Total Dissolved Solids (TDS) | Below 1,500-2,000 ppm above fill water | Measures total mineral load | Rarely an issue | Dull water, reduced chemical performance |
Free Chlorine: Your Pool's Front Line
Free chlorine (FC) is the active form of chlorine available to kill pathogens and prevent algae. The CDC recommends at least 1 ppm of free chlorine in residential pools, though most pool professionals target 2-4 ppm for a reliable safety margin. In Southern California, HASA liquid chlorine is the go-to product because it adds no calcium or stabilizer - keeping those already-high numbers from climbing further.
I consider free chlorine levels the first thing to check any time a pool looks "off." If FC reads zero, nothing else you adjust will matter until you restore sanitizer.
Pool pH Levels: The Master Controller
pH measures how acidic or basic your water is on a 0-14 scale. The sweet spot sits between 7.4 and 7.6. At that range, chlorine stays effective, surfaces stay protected, and swimmer comfort peaks. Every tenth of a point above 7.6 chips away at chlorine's killing power, so even small pool pH swings carry real consequences. You lower pH with muriatic acid and raise it with soda ash (sodium carbonate).
Pool Alkalinity: The pH Buffer
Total alkalinity (TA) acts as a buffer that prevents pH from lurching after every splash or chemical dose. Target 80-120 ppm. When pool alkalinity drops too low, pH becomes a roller coaster. When it climbs too high, pH drifts upward and the water can turn hazy. Sodium bicarbonate (yes, baking soda) raises TA without dramatically pushing pH. That is why it is one of the most-used chemicals in pool care.
Calcium Hardness: The Surface Protector
Calcium hardness (CH) measures dissolved calcium in parts per million. Pools with plaster finishes need 200-400 ppm. Too little calcium and the water becomes "hungry," pulling calcium right out of your plaster, grout, and metal fittings. Too much and you get the chalky scale deposits that plague so many LA pools. Because our tap water often arrives near 200 ppm, SoCal pool owners rarely need to add calcium chloride. The bigger battle in hard water pool maintenance? Keeping calcium from climbing above 400.
Cyanuric Acid: Chlorine's Sunscreen
Cyanuric acid (CYA) - also called stabilizer or conditioner - wraps around free chlorine molecules and slows UV degradation from sunlight. Without it, direct LA sun can destroy up to 90 percent of unprotected chlorine in just a couple of hours. The ideal range for cyanuric acid in a pool is 30-50 ppm. Push above 70-80 ppm and you run into trouble: chlorine molecules become so tightly bound to CYA that they can no longer kill bacteria, a condition known as chlorine lock.
Total Dissolved Solids: The Invisible Ceiling
TDS counts every dissolved substance in the water - salts, minerals, chlorine byproducts, body oils, sunscreen residue, and more. Most industry guidance suggests action when total dissolved solids in a pool exceed 1,500-2,000 ppm above the original fill water level. In LA, where fill water already carries 300-500+ ppm of dissolved minerals, pools can approach that ceiling years sooner than pools filled with softer water.
When TDS gets too high, chlorine struggles, water looks dull, and the only real fix is a partial drain and refill. Most competitor guides don't even mention TDS, yet it is one of the most frequent reasons we recommend draining at our stores.
How Southern California Hard Water Changes the Game
What Sets LA Tap Water Apart
Three factors make Los Angeles tap water different from most of the country:
- High baseline calcium from Colorado River water and local groundwater.
- Elevated TDS at the tap - often 300-500+ ppm before any pool chemicals enter the picture.
- Seasonal variation - in drier months, mineral concentrations in the supply can spike.
The Two Hard-Water Problems We See Most
From four decades of in-store pool water testing, two patterns repeat more than any others:
- Rapid scale formation. High calcium combined with pH above 7.8 creates ideal conditions for calcium carbonate deposits on tile lines, inside heaters, and on salt chlorine generator cells.
- Accelerated TDS buildup. Because the starting TDS is already elevated, evaporation concentrates minerals faster, and pools hit the TDS ceiling well before the typical five-to-seven-year timeframe that textbooks cite for softer-water regions.
Both problems share the same long-term solution: a partial drain and refill with fresh water to reset mineral levels.
How the Six Pool Chemistry Parameters Work Together
Pool chemistry is a system, not six independent dials. Adjust one and the others respond.
The Right Order: Alkalinity, Then pH, Then Sanitizer
Always correct total alkalinity first, then pH, then chlorine. Here is why:
- Adjust total alkalinity with sodium bicarbonate (to raise) or muriatic acid (to lower).
- Correct pH with muriatic acid (to lower) or soda ash (to raise).
- Dose sanitizer once TA and pH sit in range so chlorine works at peak strength.
Skipping ahead to sanitizer while TA or pH drifts wastes chemicals and money.
The Saturation Index Tells You Where Your Water Stands
The Langelier Saturation Index (LSI) combines your water temperature, pH, total alkalinity, calcium hardness, and TDS into a single number that predicts whether your water will scale or corrode.
- An LSI near zero means balanced water.
- A positive LSI signals scaling risk.
- A negative LSI means the water is corrosive.
In Southern California pool care, the combination of warm temperatures, high calcium, and elevated TDS pushes LSI positive more often than most owners realize. That is why scaling tops our complaint list.
The Chlorine-CYA Relationship and Chlorine Lock
CYA protects chlorine from the sun, but too much CYA smothers it. When CYA exceeds roughly 70-80 ppm, a growing percentage of free chlorine becomes bound and inactive. Your test kit may show 3 ppm of free chlorine, yet the water grows algae because the effective sanitizer available is near zero. The only reliable fix for chlorine lock is dilution: drain a portion of the pool and refill with fresh water to bring CYA back into the 30-50 ppm range.
Pool Water Testing: When and How Often
Weekly Testing Baseline
At minimum, test free chlorine and pH twice a week, and check total alkalinity, calcium hardness, and CYA once a week. A liquid reagent test kit (like a DPD or FAS-DPD kit) delivers more precise readings than test strips, especially for free chlorine and CYA.
Seasonal Adjustments for LA's Climate
Los Angeles pools run year-round. In summer, higher water temperatures and stronger UV burn through chlorine faster. Test free chlorine and pH three times a week from June through September. CYA deserves a check every two weeks during peak sun because stabilizer does not break down naturally - it only increases through addition or leaves through splash-out and backwashing.
After Rain, Parties, and Refills
Test within 24 hours of any event that changes water volume or introduces contaminants:
- Rain dilutes chemicals and can drop pH and alkalinity.
- Pool parties spike combined chlorine from sweat, sunscreen, and organic matter.
- Partial refills reset TDS and calcium baselines, so re-test everything.
| Testing Trigger | Parameters to Check |
|---|---|
| Twice weekly (routine) | Free chlorine, pH |
| Weekly (routine) | Total alkalinity, calcium hardness, CYA |
| Monthly | TDS |
| After rain | pH, TA, FC |
| After a party or heavy use | FC, combined chlorine |
| After a partial drain and refill | All six parameters |
Five Pool Chemistry Mistakes LA Owners Keep Making
After four decades and thousands of water-test consultations, we keep running into the same errors.
Over-Stabilizing with CYA
Adding stabilized chlorine (dichlor or trichlor tablets) every week piles CYA higher and higher. CYA has no natural exit from the pool, so levels can reach 100+ ppm by mid-summer. The result is chlorine lock. Use unstabilized liquid chlorine - like HASA - for regular dosing, and reserve stabilized products for the initial CYA bump in spring.
Forgetting About TDS Until the Damage Shows
Because TDS is invisible and rarely tested at home, most pool owners learn about it only when their water starts looking flat and dull despite perfect chlorine readings. Test TDS at least once a month, or bring a water sample to any Discount Pool Mart location for a free comprehensive test.
Chasing pH Without Fixing Alkalinity First
We see this almost daily. A pool owner dumps acid to bring pH down, and it bounces right back up within days. The culprit is nearly always high total alkalinity pushing pH upward. Fix TA first, and pH often corrects itself.
Using Calcium-Based Shock in Hard Water
Calcium hypochlorite (cal-hypo) shock adds calcium to every dose. In a region where tap water already delivers 200+ ppm of calcium, repeated cal-hypo treatments accelerate scaling. Liquid chlorine or a non-chlorine oxidizer shock avoids this entirely.
Skipping Winter Pool Water Testing
In colder states, pools close for winter. In LA, they stay full and exposed to sunlight twelve months a year. Skipping tests from October through March is a recipe for algae blooms and scaling that cost far more to fix come spring. Southern California pool care does not get a true off-season.
Your Water Chemistry Learning Path
This pool chemistry guide covers the big picture. For step-by-step instructions and specific troubleshooting, explore these focused resources:
- How to Test Your Pool Water - choosing between test strips and liquid reagent kits, reading results accurately, and knowing when a professional retest makes sense.
- Step-by-Step Water Balancing - the exact process for adjusting TA, pH, and chlorine in the right order with the right chemicals.
- Understanding Cyanuric Acid - the full story on stabilizer, chlorine lock thresholds, and how to bring CYA back into range.
- Preventing Algae Through Chemistry - how proper chlorine, pH, and phosphate management stops algae before it starts.
- Why LA Pools Love HASA Liquid Chlorine - the benefits of sodium hypochlorite in a hard-water region and how to dose it correctly.
- Fixing Cloudy Pool Water - diagnosing the real cause (filtration, chemistry, or both) and clearing it up fast.
Each guide picks up exactly where this page leaves off.
Pool Water Chemistry FAQ
What are the ideal pool chemical levels? The six readings to watch: free chlorine (2-4 ppm), pH (7.4-7.6), total alkalinity (80-120 ppm), calcium hardness (200-400 ppm), cyanuric acid (30-50 ppm), and TDS (below 1,500-2,000 ppm above fill water). Keeping all six in range produces safe, clear, comfortable water.
In what order should I add pool chemicals? Follow this sequence: (1) adjust total alkalinity, (2) correct pH, (3) dose sanitizer. Alkalinity buffers pH, so fixing it first prevents pH from bouncing right back out of range after treatment.
What does baking soda do to pool water chemistry? Baking soda (sodium bicarbonate) raises total alkalinity without a large impact on pH. It is the standard product for bringing TA up into the 80-120 ppm range and stabilizing pH swings.
How often should I test my pool water in Los Angeles? Test free chlorine and pH at least twice a week year-round. Check TA, calcium hardness, and CYA weekly. Test TDS monthly. After rain, parties, or a refill, re-test right away. LA's year-round sun and warm temperatures mean pools never get a true off-season.
What is chlorine lock and how do I fix it? Chlorine lock occurs when cyanuric acid climbs above roughly 70-80 ppm, binding so tightly to free chlorine that it can no longer sanitize. The only reliable fix is a partial drain and refill to dilute CYA back into the 30-50 ppm range. Adding more chlorine will not solve the problem.
Why does my pool stay cloudy even with good chlorine? Cloudiness with adequate chlorine often points to high total alkalinity, high calcium hardness, poor filtration, or elevated TDS. In LA's hard water, calcium carbonate precipitation is a frequent culprit. A full water test that includes TDS and calcium will usually reveal the answer.
Visit any of our 8 Los Angeles-area Discount Pool Mart stores for a free water test. Bring a sample, and we will measure all six pool chemistry parameters, check your saturation index, and walk you through exactly what your pool needs. Forty years of SoCal pool care is behind every recommendation we make.