Pool Chemical FAQ

Every pool needs just a few core chemicals: a sanitizer (chlorine or bromine), something to control pH (muriatic acid to lower, soda ash to raise), and a stabilizer (cyanuric acid/CYA) to protect chlorine from UV. That's it for the essentials. Optional additions include algaecide, phosphate remover, clarifier, and calcium hardness increaser. Most pool stores will try to sell you 15+ products — the reality is simpler than they want you to believe.

Always fix chemistry in this order: (1) Total Alkalinity first — it affects everything else, (2) pH second — it determines how effective your chlorine is, (3) Calcium Hardness — especially important in Austin's hard water, (4) CYA/Stabilizer — protects your chlorine from sunlight, (5) Chlorine last — once everything else is balanced, chlorine works efficiently. Never add multiple chemicals at the same time. Wait at least 30 minutes between additions, with the pump running.

Chlorine tablets (trichlor) are convenient but they do three things simultaneously: add chlorine, lower pH, AND add cyanuric acid (CYA). Over time, CYA builds up and makes chlorine less effective — this is the #1 problem we see in DIY pools in Steiner Ranch and Lakeway. If your CYA exceeds 70-80 ppm, even high chlorine levels won't prevent algae. The solution is to use liquid chlorine (which doesn't add CYA) and manage pH separately with muriatic acid.

Liquid chlorine (sodium hypochlorite/bleach): Adds only chlorine, no CYA buildup, no pH change. Best for regular dosing. Short shelf life (loses potency in 3-4 weeks, faster in Texas heat). Tablets (trichlor): Slow-dissolving, convenient, but adds CYA with every tablet. Great for vacation feeders, problematic as your only chlorine source long-term. Granular shock (cal-hypo): Fast-dissolving, no CYA, but adds calcium — already high in Austin water. Dichlor shock adds CYA. For Austin pools, liquid chlorine is the gold standard for regular maintenance.

Three reasons in Austin: (1) UV sunlight — without adequate CYA (stabilizer), the sun destroys 90% of your chlorine in 2 hours. Keep CYA at 30-50 ppm. (2) Heat — warmer water breeds more bacteria and algae, consuming chlorine faster. A 90°F pool uses chlorine roughly twice as fast as an 80°F pool. (3) Organic load — pollen, leaves, body oils, sunscreen all consume chlorine. In peak Austin summer, you may need to add chlorine 2-3 times per week instead of once.

Shocking means raising chlorine to 10x or more above normal levels to kill algae, bacteria, and break down chloramines (the "chlorine smell" that actually means too LITTLE free chlorine). Shock when: the pool looks cloudy or green, you smell strong chlorine odor (that's chloramines), after heavy rain, after a pool party with many swimmers, or when chlorine demand is high and levels won't hold. Always shock at dusk — sunlight destroys unstabilized shock chlorine rapidly.

No. "Chlorine lock" is a myth perpetuated by some pool stores to sell you unnecessary products. What's actually happening when chlorine "isn't working" is almost always high CYA (cyanuric acid). When CYA exceeds 70-80 ppm, chlorine becomes so bound up that it can't effectively sanitize. The fix isn't a magic product — it's partially draining the pool and refilling with fresh water to dilute the CYA. This is why we recommend liquid chlorine over tablets for regular use.

Austin's tap water comes from a limestone aquifer — it's naturally high in calcium and alkalinity, which constantly pushes pH upward. Additionally, if you have a salt chlorine generator, the electrolysis process itself raises pH. Aeration from water features (waterfalls, bubblers, fountains) also drives pH up. Most Austin pool owners need to add muriatic acid weekly, sometimes twice a week. This is completely normal for our water chemistry.

Muriatic acid (hydrochloric acid, typically 31.45% concentration) is the most common pool acid used to lower pH and alkalinity. It's effective and inexpensive but requires respect: always add acid to water, never water to acid. Pour slowly around the pool perimeter with the pump running. Wear chemical-resistant gloves and eye protection. Never mix with chlorine — this creates toxic chlorine gas. Store outside, never in an enclosed garage in Texas summer heat. If you're uncomfortable handling it, that's a great reason to hire a professional.

pH measures how acidic or basic your water is right now (target: 7.4-7.6). Alkalinity is your water's ability to resist pH changes — think of it as a pH buffer (target: 80-120 ppm). High alkalinity makes pH hard to change and tends to push pH upward. Low alkalinity makes pH bounce around wildly. Always adjust alkalinity first, then fine-tune pH. In Austin, our tap water fills pools with high alkalinity, so most corrections involve lowering it with muriatic acid.

At pH 7.4, chlorine is about 50-60% effective as a sanitizer. At pH 8.0, it drops to about 20% effective — meaning you need 3x more chlorine to get the same sanitation. High pH also causes calcium to precipitate out of solution, forming scale on tile, equipment, and salt cells. Low pH corrodes metal equipment, etches plaster surfaces, and irritates skin and eyes. In Austin's heat, where chlorine is already under stress, keeping pH in range is the difference between a clean pool and an algae bloom.

Cyanuric acid (CYA) acts as sunscreen for your chlorine. Without it, Austin's intense UV radiation destroys 90% of your chlorine within 2 hours. With proper CYA (30-50 ppm), chlorine lasts throughout the day. CYA bonds loosely with chlorine molecules, protecting them from UV while still allowing them to sanitize. It's essential for any outdoor pool in Texas. However, too much CYA (above 70-80 ppm) makes chlorine sluggish and ineffective.

There is only one reliable way to lower CYA: drain and dilute. Partially drain your pool (25-50% depending on how high CYA is) and refill with fresh water. No chemical, enzyme, or product reliably removes CYA from pool water despite marketing claims. This is the single biggest problem we see in pools that have used trichlor tablets for years — CYA slowly creeps up with every tablet until chlorine becomes ineffective. Prevention is better: use liquid chlorine for regular dosing and tablets only sparingly.

Austin sits on a limestone aquifer (Edwards Aquifer), giving us water that's naturally high in calcium (200-300+ ppm from the tap), high in alkalinity, and has a pH that constantly pushes upward. Add intense UV radiation, 100°F+ summer temps that accelerate chlorine consumption, cedar pollen (December-March) loaded with phosphates, and oak leaf debris year-round — Austin is one of the more challenging pool chemistry environments in the country. Pools here need more acid, more chlorine in summer, and more vigilant monitoring than pools in softer-water regions.

That's calcium scale — calcium carbonate deposits from Austin's hard water. It forms at the waterline where water evaporates and leaves mineral deposits behind. Prevention: keep pH below 7.6 and calcium hardness below 400 ppm (difficult with our tap water). Regular brushing helps. For existing scale, you can use a pumice stone on plaster and tile (never on vinyl or fiberglass), or hire a professional bead/salt blasting service. Muriatic acid dilutions can dissolve light scale. Severe scale on tile usually requires professional removal.

Cedar pollen is too fine for most skimmer baskets to catch. It floats on the surface and passes through some filters. Here's the protocol: (1) Run your pump 24/7 during peak cedar season (January-February). (2) Add a clarifier or flocculant to help the filter grab fine particles. (3) Use a skimmer sock over your basket for finer filtration. (4) Brush walls and floor frequently — pollen settles and feeds algae. (5) Add extra chlorine — the organic phosphates in pollen consume chlorine. (6) Consider a phosphate remover if levels exceed 300 ppb. This is temporary — it passes by March.

Maybe. Phosphates are algae food — they don't cause algae directly (that requires low chlorine), but they make algae blooms more aggressive when chlorine does drop. Austin pools naturally accumulate phosphates from pollen, leaves, fertilizer runoff, and even tap water. If your phosphate levels exceed 300 ppb and you struggle with recurring algae, a phosphate remover like PHOSfree can help. However, if your chlorine is properly maintained, phosphates are less of a concern. Think of phosphate removal as insurance, not a replacement for proper chlorine management.

Critical rules: NEVER mix chlorine and muriatic acid — produces deadly chlorine gas. NEVER mix different types of chlorine (liquid + tablets, or cal-hypo + trichlor) — can cause fire or explosion. NEVER mix chlorine and algaecide directly — add to pool separately. NEVER add water to acid — always acid to water. Wait at least 30 minutes between adding different chemicals to the pool, with the pump running. When in doubt, add one chemical, run the pump for an hour, then add the next.

Texas garages can hit 140°F+ in summer — too hot for most chemicals. Liquid chlorine loses potency rapidly above 75°F and has a shelf life of just 3-4 weeks in heat. Store it in the coolest, shadiest spot possible. Muriatic acid is more heat-stable and can be stored outside (it doesn't freeze either). Dry chemicals (tablets, shock, CYA) should be in sealed containers in a cool, dry area — moisture causes them to react. Never store chlorine products and acid products next to each other. Keep all chemicals off concrete (acid drips etch it) and away from pets and children.

Shelf life in Austin conditions: Liquid chlorine — 3-4 weeks (loses ~50% potency per month in heat). Trichlor tablets — 3-5 years sealed, but degrade once opened and exposed to moisture/heat. Cal-hypo shock — 1-2 years sealed. Muriatic acid — virtually indefinite. CYA (granular) — indefinite if kept dry. Algaecide — 3-5 years unopened. Test strips — 1-2 years (store sealed, away from moisture). Buy liquid chlorine in small quantities and use it fast. Buy dry chemicals once a season.

The Taylor K-2006 is the gold standard for homeowners — it uses liquid reagent drops (DPD/FAS method) and measures Free Chlorine, Combined Chlorine, pH, Alkalinity, CYA, and Calcium Hardness with lab-grade accuracy. Cost: about $80-100. For a budget option, the Taylor K-2005 or TF-100 (sold by TFTestKits.com) are excellent. Test strips are convenient but less accurate — fine for a quick chlorine/pH check between proper tests, but don't rely on them exclusively. Avoid the cheap 5-in-1 strips from big box stores.

Minimum: Chlorine and pH twice per week (these change fastest, especially in Austin heat). Alkalinity once per week. CYA once per month (it changes slowly unless you're adding trichlor tablets). Calcium hardness once per month. After events that stress chemistry: heavy rain, pool party, extreme heat wave, or chemical additions — test again within 24 hours. During cedar pollen season or green pool recovery, test daily until chemistry stabilizes.

Pool store tests are useful for a second opinion and for tests you can't do at home (like phosphates, metals, or TDS). However, be aware that pool stores are in the business of selling chemicals — some will recommend products you don't need. Always bring a fresh sample (collected elbow-deep, away from returns) in a clean container. Compare their results with your own home test. If they suggest 5+ products, get a second opinion. A well-maintained pool rarely needs more than chlorine, acid, and occasional CYA.