What chemicals do you actually need for a pool?
Walk into a pool supply store and you'll see shelves full of bottles, bags, and buckets all claiming to be essential. Most of them aren't. Here's what you actually need, what each chemical does, and what you can safely skip.
The essentials
These are the chemicals every pool needs. You'll use them regularly throughout the season.
| Chemical | What It Does | How Often You'll Use It |
|---|---|---|
| Liquid chlorine (sodium hypochlorite) | Sanitizes the water. Kills bacteria and algae | Weekly or as needed when FC drops |
| Muriatic acid | Lowers pH and total alkalinity | Weekly or as needed. Most pools trend high |
| Baking soda (sodium bicarbonate) | Raises total alkalinity | Occasionally. Usually at season start |
| Cyanuric acid (CYA / stabilizer) | Protects chlorine from UV breakdown | Once at season start. Doesn't break down |
| Calcium chloride | Raises calcium hardness to protect surfaces | Once or twice a season |
That's it. Five chemicals cover 90% of what a residential pool needs all season.
A closer look at each one
Chlorine
Chlorine is your sanitizer. Without it, bacteria and algae take over within days. You have a few options:
- Liquid chlorine (bleach) — The simplest option. Pure sodium hypochlorite. No additives, no stabilizer, no residue. This is what most experienced pool owners use
- Chlorine tablets (trichlor) — Convenient but contain CYA. Over time, tablets cause CYA to build up and make chlorine less effective. Fine for convenience, but watch your CYA level
- Cal-hypo (granular shock) — Fast-dissolving. Good for shocking but adds calcium. Not ideal for regular use in hard-water areas
Which chlorine should you use?
Liquid chlorine is the best all-around choice. It doesn't add CYA, calcium, or other byproducts. Tablets are fine if you monitor CYA closely. For a detailed comparison, see our guide on liquid chlorine vs tablets.
Muriatic acid
pH naturally drifts upward in most pools, especially saltwater pools. Muriatic acid brings it back down. It also lowers total alkalinity when needed. You'll use this more than almost anything else.
Buy it by the gallon. Pool-grade muriatic acid is typically 31.45% strength. You can also use dry acid (sodium bisulfate) if you prefer granular form, but liquid is cheaper and more precise.
Baking soda
Raises total alkalinity without significantly affecting pH. Regular grocery store baking soda works perfectly. It's the same chemical (sodium bicarbonate) as the pool store version at a fraction of the price.
Don't confuse it with soda ash (sodium carbonate), which raises pH more than alkalinity. Different chemicals, different jobs. See our baking soda vs soda ash guide for details.
Cyanuric acid (stabilizer)
CYA acts like sunscreen for your chlorine. Without it, UV light destroys free chlorine in a few hours. With it, your chlorine lasts all day. Target 30-50 ppm for most pools.
Add it once at the start of the season. It doesn't break down or evaporate, so it only leaves the pool through splash-out, backwashing, or draining. If you use stabilized tablets (trichlor), CYA builds up on its own.
Calcium chloride
Raises calcium hardness. Low calcium causes the water to pull minerals from your pool surfaces, leading to etching, pitting, and damage over time. Target 200-400 ppm.
Most pools only need this at startup or after a partial drain. Calcium doesn't leave the water on its own, so once you're in range, you're good.
Chemicals you might need sometimes
| Chemical | When You Need It |
|---|---|
| Soda ash (sodium carbonate) | When pH is low but alkalinity is fine. Raises pH without raising TA as much as baking soda |
| Pool salt | Saltwater pools only. Replenish when levels drop below your SWG's recommended range |
| Algaecide | Preventive use in pools prone to algae. Not a substitute for proper chlorine levels |
| Metal sequestrant | If you have well water or notice staining. Binds metals so they don't deposit on surfaces |
| Clarifier or flocculant | For persistent cloudiness after chemistry is balanced. Clarifier clumps particles for the filter. Floc drops them to the bottom for vacuuming |
What you can skip
The pool store will try to sell you a lot of products you don't need:
- "Shock" products — Shocking is just adding extra chlorine. You can do this with regular liquid chlorine. No need for a special product
- Phosphate remover — If your chlorine is at the right level, algae can't grow regardless of phosphates. Phosphate removers solve a problem that proper sanitation already handles
- Water "polisher" or "enhancer" — Marketing terms. If your chemistry is balanced, the water will be clear
- Enzyme treatments — Can help with organic buildup (oils, lotions) but are optional. Good chlorine levels handle most of this
- Multi-purpose "all-in-one" treatments — These combine chemicals in fixed ratios that rarely match what your pool actually needs. Always adjust chemicals individually based on your readings
The pool store business model
Pool stores make money selling products. The more products you buy, the better for them. In reality, balanced water chemistry with five basic chemicals covers nearly everything. Test your water, know your numbers, and add only what's needed.
How much to buy for the season
For a typical 15,000-gallon residential pool during a full season:
| Chemical | Estimated Season Supply | Approximate Cost |
|---|---|---|
| Liquid chlorine (10%) | 20-30 gallons | $60-90 |
| Muriatic acid | 4-8 gallons | $30-50 |
| Baking soda | 5-10 lbs | $5-10 |
| CYA (stabilizer) | 2-4 lbs (one-time) | $15-25 |
| Calcium chloride | 5-10 lbs (if needed) | $15-20 |
Total cost for a full season of chemicals: roughly $125-195. Compare that to the hundreds you'd spend buying specialty products at the pool store.
Know exactly what to add
PoolChem Tracker calculates the right amount of each chemical based on your pool size and current readings. No guesswork, no waste, no overbuying.
Keep reading
- Pool Chemistry for Beginners: 5 Key Numbers — understand what each chemical is targeting
- Pool Startup Chemicals Checklist — what to buy and the order to add everything
- Liquid Chlorine vs Tablets — pros and cons of each chlorine type
- How to Balance Pool Water in 4 Steps — the correct order for adjusting chemicals