Pool School — Water, Settled
Straight answers, less is more, no upsell. The water's simpler than they told you.
Most pool problems come from doing too much, not too little. A balanced pool needs a handful of numbers in range and enough chlorine to do its job — not a shopping cart of bottles.Less is more; more chemicals usually means more problems. Here's everything you need, in plain English, whether it's your first summer or your tenth.
Learn the basics
Start here if you're new. The whole of pool care in a few short reads.
Less Is More: The Whole of Pool Care in One IdeaStart here. The one idea that makes every other pool problem simple — and cheaper.How to Test Your Pool Water (and Why Strips Lie to You)Strips and store tests hide the two numbers that matter most. Here's how to read your water for real — and the one kit to own.Do I Still Have to Test a Salt Water Pool?A salt system makes chlorine, not decisions. Here's what you still test — and the two numbers salt quietly pushes out of range.How Fountains, Bubblers & Spillovers Change Your WaterFountains, bubblers, and spillovers all aerate the water — which raises pH, uses a bit more chlorine, and cools the pool. Here's how to work with it.
Above-ground pools
Got an above-ground pool? Different gear, same water chemistry. Start here.
Gear hub🏊 Above-Ground Pools →Every above-ground showdown in one place — filters, pumps, and more, sorted by the job.What Size Above-Ground Pool Pump Do I Need? (It's GPM, Not Horsepower)Sizing an above-ground pump is a flow (GPM) problem, not a horsepower one. Match the pump to your pool's gallons AND your filter's rated GPM — bigger HP filters worse, not better. The turnover math, the filter ceiling, and how to replace a dead pump.Sand Filter vs. Cartridge Filter for an Above-Ground Pool: Which Do You Need?Cartridge for a small pool (simpler, finer, no backwashing); sand once you get bigger (the media lasts years). The crossover is around 10,000–12,000 gallons. The honest comparison, no upsell.How to Close a Pool for Winter (Hard-Freeze Close vs. Florida "Winter Mode")Freeze country closes the pool. Florida doesn't. Both procedures step by step — in-ground, above-ground, and the freeze-night plan for warm climates.How to Open a Pool in Spring (Without Buying a Start-Up Kit)Open early, chlorinate immediately, test before you buy anything. The in-ground and above-ground opening sequence, plus the ammonia check that stops a spring disaster.
Myths, settled
The pool-store gospel, fact-checked. A little reality, so you stop buying bottles you don't need.
Myth, settledDo You Have to Shock Your Pool Every Week?No. 'Shock' is a chlorine level you reach for a problem — not a weekly product or ritual.Myth, settledAre Salt Water Pools Chlorine-Free?No. A salt pool IS a chlorine pool — the cell just makes the chlorine for you, from salt.Myth, settledDo You Need Phosphate Remover?For almost every pool, no. Enough chlorine kills algae no matter how many phosphates feed it.Myth, settledDo You Need Algaecide?No. Proper chlorine prevents algae. Skip routine algaecide — and avoid the copper ones entirely.Myth, settledDo You Have to Run Your Pool Pump 24/7?No. A few hours to skim and mix your chemicals is plenty — chemistry sanitizes the pool, not laps through the filter.Myth, settledIs a Copper or Mineral Pool Chlorine-Free? (Is Copper Safe in a Pool?)Copper kills algae, but it's not a sanitizer, it stains, and it never leaves. A 'mineral pool' just runs less chlorine — not none.Myth, settledIs Bleach a Good Alternative to Pool Chlorine, or a Myth?Bleach is the exact same chemical as pool 'liquid chlorine,' just weaker. It works fine. The only catches are strength and cost — use plain unscented, and buy fresh.Myth, settledIs Pool-Store 'Alkalinity Up' Just Baking Soda? (Pool & Hot Tub)It's the identical chemical — sodium bicarbonate — at several times the price. Baking soda raises alkalinity, not pH. What it does, how much, and the hot-tub version.
Fix a problem
Jump straight to what you're dealing with. Answer first, the why underneath.
Start here🩺 Diagnose My PoolPick your symptom, enter a couple of numbers, get the diagnosis + exact target + fix. The fast way in.My Pool Is Green — How to Clear It (the SLAM Method)Green, cloudy, or hazy water; algae on the walls or floor.Green but My Chemical Levels Look Fine?Algae or cloudiness, but your test (or the pool store) says chlorine is fine.Mustard Algae That Comes Back (When Levels Are Good)Yellow/mustard (or green-yellow) dust on shaded walls and floor that brushes away and returns.Are Pool Stores a Scam? The Honest AnswerYou leave the pool store with a cart of chemicals and a printout — every time.Strong Chlorine Smell and Burning Eyes? You Need More Chlorine, Not LessA strong 'chlorine' smell and red, itchy, burning eyes after swimming.My Pool Is Cloudy but Not Green — What's Going On?Milky, hazy, or dull water — but it's not green and you don't see algae.CYA Too High? Why Your Chlorine Quit (and How to Actually Lower It)Your chlorine 'reads fine' but does nothing — or the pool store told you the pool has 'chlorine lock.'How to Recover Your Pool After Wildfire Ash, Smoke, or a StormWildfire ash, heavy smoke, or storm debris just fouled your pool — gray or cloudy water, a chlorine that won't hold, and gunk settling on the bottom.Pool Stains, Scale & Scum: What Each Mark Is and How to Remove ItA brown stain, a white crust, a greasy waterline ring — four different marks, four different fixes. How to tell them apart, remove each (the cheap way), and keep them gone.Black Algae in a Pool: Why It Keeps Coming Back (and How to Actually Kill It)Dark black or blue-green spots that come back after brushing and shrug off shock
Seasonal & away
Closing, opening, and leaving town — the calendar jobs, done in order. In-ground and above-ground both covered.
How to Prep Your Pool Before Vacation (So You Don't Come Home to Green)The leave-it-safe checklist — build a chlorine reserve, raise FC before you go, run the pump, cut the sun. Come home to clear water, not green.How to Close a Pool for Winter (Hard-Freeze Close vs. Florida "Winter Mode")Freeze country closes the pool. Florida doesn't. Both procedures step by step — in-ground, above-ground, and the freeze-night plan for warm climates.How to Open a Pool in Spring (Without Buying a Start-Up Kit)Open early, chlorinate immediately, test before you buy anything. The in-ground and above-ground opening sequence, plus the ammonia check that stops a spring disaster.
Calculate
Exact doses and targets — no guessing, no overshooting.
Free · on-device📈 Pool TrackerLog every test, get each number judged against your pool's target + the exact dose, and watch the trends. Free, on-device, no account.Chemical dosing calculatorHow much of what to move any level — chlorine, pH, alkalinity, calcium, stabilizer, salt.Pool volume calculatorHow many gallons is your pool? Every dose starts here.Salt vs. chlorine cost calculatorIs a salt system actually cheaper for your pool?
Look it up
The charts, definitions, and how-it-works guides — grouped by topic, for when you just need the number.
Water chemistry
The 5 Numbers That Matter (and Their Target Ranges)Target ranges for every level, plus the FC/CYA chart — the single most important table in pool care.When Is It Safe to Swim After Adding Chemicals?Wait times for chlorine, acid, shock, CYA and more — and the one test that actually decides it.Water Balance: Is Your Pool Corrosive or Scaling? (LSI/CSI, Plainly)Your numbers can each be 'in range' and the water still corrode or scale. The one index that ties them together — plainly, no products.How Chlorine and CYA Actually Work (the Science Behind the FC/CYA Chart)Why free chlorine has to rise with CYA — the hypochlorous-acid science behind the FC/CYA chart, plainly.How to Remove Metal Stains with Ascorbic Acid (the Full Procedure)Ascorbic acid lifts iron stains fast — but it moves the metal into the water, it doesn't remove it. The full ordered procedure + the sequester-or-it-comes-back catch.
Chlorine & salt
Chlorine Alternatives for Pools: What Actually Replaces It (Salt, Ozone, UV, Ionizers, Bromine)Salt is chlorine. Ozone, UV, and mineral systems only reduce it — they carry no residual, so you still chlorinate. One system is truly chlorine-free (biguanide), and it's a downgrade for almost everyone.Why a Salt Pool Scales Faster — and How to Fix Calcium BuildupThe white crust on your salt cell and tile isn't the salt's fault — it's calcium and pH. Why a salt pool scales faster, and the step-by-step fix (no anti-scale bottle required).Which Chlorine Should You Use? Ranked by What Else It Puts in Your WaterLiquid, tablets, cal-hypo, dichlor, salt — same sanitizer, different baggage. Ranked by what else each one adds to your water (and when to break the rule).How Long Does a Salt Cell Last? (And How to Make Yours Last Longer)Rated in hours, not years — usually 3–7. Why the cell wears out, the real ways to make it last longer (oversize it, don't over-clean it), and how to tell when it's done.
Equipment & filtration
Will a Pool Robot Wear Down Your Pool's Finish? (Vinyl, Fiberglass, Plaster)A well-matched robot won't wear your finish faster — how vinyl, fiberglass, and plaster differ, and why steps and shelves are about coverage, not wear.Sand vs. Glass vs. Filter Balls: What to Put in Your Sand FilterYour sand filter can run traditional sand, recycled glass, or poly-fiber filter balls. Glass is the upgrade most people should make; sand is the safe default; filter balls are the lightweight wildcard. The honest comparison.What Size Above-Ground Pool Pump Do I Need? (It's GPM, Not Horsepower)Sizing an above-ground pump is a flow (GPM) problem, not a horsepower one. Match the pump to your pool's gallons AND your filter's rated GPM — bigger HP filters worse, not better. The turnover math, the filter ceiling, and how to replace a dead pump.Sand Filter vs. Cartridge Filter for an Above-Ground Pool: Which Do You Need?Cartridge for a small pool (simpler, finer, no backwashing); sand once you get bigger (the media lasts years). The crossover is around 10,000–12,000 gallons. The honest comparison, no upsell.Pool Pump & Filter Troubleshooting: Won't Prime, High Pressure, Noises, No FlowA symptom-first troubleshooter — high pressure, no flow, won't prime, noises, drips, sand in the pool. The free fix first, the real part only when it's earned.Why Isn't My Pool Heating? (Heater Basics + the No-Heat Checklist)Which heater fits your pool, the no-heat checklist (usually a free fix), sizing, and the one move that cuts heating cost 50–70%.
Pool build & materials
Concrete (Plaster) vs. Fiberglass vs. Vinyl: The Honest Pool-Type ComparisonThe three ways to build a pool — concrete/gunite (plaster or aggregate finish), fiberglass, and vinyl-liner — compared honestly on durability, cleanability, longevity, maintenance, and cost. Plus the Florida water-table and saltwater factors.Pool Cage Screen Types: Which Mesh Should Go in Your Enclosure (and What It Costs)Every pool-cage screen mesh compared — 18x14 standard, 20x20 no-see-um, Super Screen polyester, pet screen, Florida Glass, and solar (SunTex 80/90). Benefits, drawbacks, lifespan, and a real 2026 Florida cost comparison, with the panel-by-panel strategy most cages actually use.Pool Tile Types: Porcelain vs. Glass vs. Ceramic vs. Stone (and What Each Costs)Ceramic, porcelain, glass, stone, and mosaic pool tile compared honestly — look, durability, where each can go, and real 2026 cost. Porcelain is the value pick; glass is the splurge.Pool Deck Materials: Travertine vs. Pavers vs. Concrete (Pros, Cons & Cost)Travertine, concrete pavers, poured concrete, natural stone, porcelain, and brick compared for a pool deck — heat underfoot, slip, salt, and real 2026 cost. Pavers are the value; travertine stays coolest.You Just Filled Your Pool — What to Do Next (New Fill & New Plaster Start-Up)Two jobs, one phrase. The first-week checklist for any new fill, plus the high-stakes 30-day protocol for new plaster — and which start-up method actually protects the finish.
Pool School is free and independent. When a fix genuinely needs a product — a real test kit, a robot that keeps up — we'll point you to the showdown, and we say so honestly. We never sell you a bottle you don't need.