Pool chemicals for beginners
A new pool needs a test kit and six chemicals: chlorine, stabilizer (cyanuric acid), muriatic acid, baking soda, soda ash, and calcium chloride.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (8 sections)
For a 10,000-gallon pool, 13 fl oz of 10% liquid chlorine raises free chlorine by 1 ppm. Everything else on the shelf is optional until a test says you need it.
The 6 chemicals (and 5 you can skip)
Pool stores sell dozens of products, but almost all of them do one of six jobs. Buy by the active ingredient and the percent on the label, not by the brand name on the front.
| Product (active ingredient) | What it does | When you use it |
|---|---|---|
| Chlorine: liquid chlorine 10–12.5% (sodium hypochlorite), or plain unscented bleach | Kills germs and algae. Measured as free chlorine (FC). | Every day or every few days, to replace what sun and swimmers use up |
| Stabilizer (cyanuric acid, CYA) | Shields chlorine from sunlight so it lasts through the day | At start-up and after you replace water; it only leaves when water leaves |
| Muriatic acid 31.45% or 14.5% (or dry acid, sodium bisulfate) | Lowers pH and total alkalinity (TA) | Whenever pH drifts above 7.6, which it does in most pools |
| Baking soda (sodium bicarbonate) | Raises total alkalinity with only a small pH change | When TA is below 80 ppm |
| Soda ash (sodium carbonate, "pH up") | Raises pH (and TA) | When pH is below 7.4, often after heavy rain or too much acid |
| Calcium chloride (calcium increaser) | Raises calcium hardness (CH) so water does not etch plaster | A few times a season in plaster pools; rarely in vinyl or above-ground pools |
"Shock" is not a seventh chemical. It is chlorine used at a higher dose. Many jugs of liquid pool chlorine have directions for both jobs. Check that yours lists shock directions on the label, and follow them. Chlorine tablets (trichlor) are convenient in a floater, but each 1 ppm of chlorine from trichlor also adds about 0.6 ppm of stabilizer (PHTA figure). If a pool uses 2 ppm a day and gets all of it from tablets, that is roughly 36 ppm more CYA in 30 days, and CYA only goes down when you drain. That is the most common way beginners end up with chlorine that "stops working." More on the trade-offs in types of pool chlorine.
Five products you can skip until a test or a specific problem tells you otherwise:
- Algaecide. Chlorine held at the right level for your stabilizer prevents algae. Algaecide is an add-on, not a replacement.
- Clarifier. Cloudy water often comes from low chlorine or a filter that needs cleaning. Check those first.
- Phosphate remover. When free chlorine stays at the right level for your stabilizer, you rarely need it. Treat it as optional, not routine.
- Metal sequestrant or stain remover. Only if your fill water contains iron or copper, or you already see stains.
- Bundled "starter kits" and "balance packs". They often contain products you do not need yet. Buy the six above one by one when a test calls for them.
What each level means
A test kit reports five or six numbers. Here is what each one tells you and the range to aim for. The ranges are the defaults in our calculators. The sources, and where they disagree, are on the methodology page. The full table is the pool chemistry chart.
| Test | What it tells you | Aim for |
|---|---|---|
| Free chlorine (FC) | How much active sanitizer is in the water right now | 2–4 ppm with no stabilizer; the minimum rises with CYA (3 ppm at CYA 40) |
| pH | How acidic the water is; affects comfort and how well chlorine works | 7.4–7.6 (acceptable 7.2–7.8) |
| Total alkalinity (TA) | How strongly the water resists pH changes | 80–120 ppm (acceptable 60–180) |
| Calcium hardness (CH) | Whether water will etch plaster or leave scale | 200–400 ppm for plaster; 150–250 ppm for vinyl, fiberglass, and above-ground |
| Stabilizer (CYA) | How well chlorine is protected from sunlight | 30–50 ppm (60–80 ppm with a salt chlorine generator) |
| Salt | Only for salt pools: fuel for the chlorine generator | Your generator's range, often around 3,200 ppm |
The one relationship to learn early: stabilizer protects chlorine but also holds part of it back, so the more CYA you have, the more free chlorine you need. The CDC's Model Aquatic Health Code says the minimum chlorine should rise with CYA (MAHC 2024 Annex, 5.7.3.1.1.2). Our rule is about 7.5% of your CYA, never below 2 ppm. See your number on the pool chlorine levels page.
Your first test
Test before you buy anything beyond chlorine. You need a kit that reads free chlorine, pH, total alkalinity, calcium hardness, and stabilizer. Strips are fine to start. A drop kit is more accurate, especially for chlorine. The guide to reading test strips shows how to get a clean reading. Enter your numbers below: the quick check tells you what to add first and how much, for the product you own.
Test in the evening or early morning, away from return jets, with the pump running. If you have just added chemicals, wait until they have circulated (at least 30 minutes for liquids) before testing again.
Week one plan
Here is a worked example from our calculator, so you can see the whole sequence once. Say you just filled a 15,000-gallon vinyl pool and the first test reads FC 0, pH 7.8, TA 90, CH 120, and CYA 0. You have 10% liquid chlorine and 31.45% muriatic acid.
- Day 1, step 1: chlorine. Add 67 fl oz of 10% liquid chlorine (FC 0 → 3.5 ppm). Pour it slowly in front of a return jet with the pump running.
- Day 1, step 2: acid, 30 minutes later. Add 10 fl oz of 31.45% muriatic acid (pH 7.8 → 7.5). Pour it into the deep end or in front of a return, never near chlorine you just added.
- Day 1, step 3: calcium, 30 minutes later. Dissolve 9.0 lb of 77% calcium chloride in a bucket of pool water first (it gets hot), then add it (CH 120 → 170 ppm). A second, smaller step on another day brings CH to 200 ppm. The total is about 14.4 lb.
- Day 1, step 4: stabilizer. Add 5.0 lb of stabilizer (CYA 0 → 40 ppm) through the skimmer or in a sock in front of a return. It dissolves slowly. Do not backwash for a few days.
- Days 2–4: test FC and pH every day. As stabilizer dissolves, your chlorine target rises from 2–4 ppm to 3–5 ppm. Add chlorine to get back into range each day and write down how much you added.
- Days 5–7: retest everything. Check CYA again (it should read close to 40 ppm), then TA and CH. From now on, your daily chlorine top-up tells you how fast your pool uses chlorine, which is the basis of your maintenance schedule.
Your numbers will differ, which is the point of the calculator above. The same plan with your volume, readings, and products is in the pool chemical calculator. The pauses between products and the reasons behind them are explained in what order to add pool chemicals.
Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling.
Buying guide: strength and price per ppm
Chlorine products differ in strength far more than in price, so compare them by cost per ppm, not cost per jug or bucket. The table shows how much of each product raises free chlorine by 1 ppm in 10,000 gallons, and what share of a gallon (liquids) or a pound (solids) that is. Multiply that share by the price you pay per gallon or per pound: the result is your cost for 1 ppm in 10,000 gallons.
| Product | Amount for +1 ppm | Share of 1 gal or 1 lb | Side effect |
|---|---|---|---|
| Liquid chlorine 12.5% | 10 fl oz | 0.080 of a gallon | no CYA or calcium added |
| Liquid chlorine 10% | 13 fl oz | 0.100 of a gallon | no CYA or calcium added |
| Household bleach 8.25% | 14 fl oz | 0.113 of a gallon | no CYA or calcium added |
| Household bleach 6% | 21 fl oz | 0.161 of a gallon | no CYA or calcium added |
| Trichlor tablets 90% | 1.5 oz | 0.093 of a pound | +0.6 ppm CYA; lowers TA as it is used |
| Cal-hypo 65% | 2.1 oz | 0.128 of a pound | +0.7 ppm calcium hardness |
| Dichlor 56% | 2.4 oz | 0.149 of a pound | +0.9 ppm CYA |
Computed with our calculator (trade percent for pool chlorine, percent by weight for bleach). Example: if 10% liquid chlorine costs you a certain price per gallon, 1 ppm in 10,000 gallons costs one-tenth of that price. Liquid chlorine loses strength in storage, and faster when hot, so buy it fresh and keep it in the shade.
Two practical rules. First, the cheapest chlorine per ppm is often not the cheapest per season if it adds stabilizer you later have to drain away. Second, read the percent on the label every time you buy: bleach sold in the same aisle ranges from 6% to 8.25%. To compare your own prices, use the pool chemical cost calculator.
Safety
- Never mix chlorine with acid, or two different chlorine products, not even in an empty bucket or scoop. Add each product to the pool separately, with the pump running.
- Add chemicals to water, never water to chemicals.
- Wear gloves and eye protection when you open containers and pour. In CDC emergency room data, a common way people get hurt is breathing fumes or dust while opening containers.
- Store chlorine and acid apart, closed, in a cool, dry place, and locked away from children and pets.
- Keep swimmers out while you add chemicals and for at least 30 minutes after acid.
- In an emergency, call Poison Control at 1-800-222-1222.
More detail in our pool chemical safety guide. Always follow the product label.
FAQ
What are some basic pool chemicals for dummies?
Chlorine to sanitize, stabilizer (cyanuric acid) to protect chlorine from the sun, muriatic acid to lower pH, baking soda to raise alkalinity, soda ash to raise pH, and calcium chloride to raise calcium hardness. Add a test kit, and you can handle routine care. Algaecides, clarifiers, and phosphate removers are optional.
What chemicals should I put in my pool when I first fill it?
Test first, then add in this order: chlorine to reach your target, acid or soda ash to bring pH to about 7.5, baking soda if alkalinity is below 80 ppm, calcium chloride if hardness is low, and stabilizer to about 30–50 ppm. Wait 30 minutes with the pump running between products. Amounts depend on your volume and readings. The calculator on this page gives them for your pool.
What chemicals go in an above ground pool?
The same six as an inground pool. Two differences: vinyl liners need less calcium (150–250 ppm is enough), and small above-ground pools need much smaller doses, so measure carefully and use your real volume. Our above-ground pool care guide covers the rest.
Sources
- CDC, Home pool and hot tub water treatment and testing: cdc.gov
- CDC, Model Aquatic Health Code 2024, Annex (5.7.3.1.1.2, chlorine and CYA): cdc.gov (PDF)
- CDC MMWR, Pool chemical injuries in public and residential settings, 2008–2017: cdc.gov
- PHTA fact sheet, Dichlor (CYA added per ppm chlorine): phta.org
- PHTA fact sheet, Sodium hypochlorite (strength loss in storage): phta.org
- Taylor Technologies, K-1005 treatment tables (chlorine, baking soda, calcium chloride amounts): PDF