💧 Not sure how much chemical to add? PoolDiag calculates exact doses for your pool size and current readings.
Try It Free →Step-by-Step Pool Opening Checklist
Pick the Right Day to Open
Don't wait until June. Algae start growing as soon as water temperatures consistently hit 60°F. Opening in early-to-mid spring — before it gets warm — makes startup chemistry far easier and prevents the "already green before I got to it" problem.
Remove and Clean the Winter Cover
Remove the cover carefully to avoid dumping debris into the water. Use a pool cover pump to remove standing water first. Rinse the cover with a garden hose, let it dry fully, then fold and store. Inspect for holes or tears that need repair before next winter.
Remove Winter Plugs and Reinstall Equipment
Pull the winter plugs from return jets and skimmer lines. Reinstall drain plugs on your pump, filter, and heater. Reinstall ladders, handrails, and pool cleaner hoses. Hand-tighten first, then use a wrench for fittings that need it. Don't overtighten plastic fittings.
Reinstall and Inspect the Filter System
Reconnect all plumbing lines between the pump, filter, and heater. Sand filters: check for channeling or clumping — sand typically needs replacing every 5–7 years. Cartridge filters: inspect for tears, cracks, or heavy calcium buildup. Replace the cartridge if the pleats are damaged.
Refill the Pool if Needed
Refill to the middle of the skimmer opening. Don't overfill — water at the top of the skimmer reduces skimming efficiency.
Prime and Start the Pump
Before starting, fill the strainer basket housing with water (this primes the pump so it doesn't run dry). Check all valves are open. Turn the pump on and watch for bubbles at the return jets — they should disappear after 1–2 minutes as air clears the lines. If the pump loses prime or runs dry for more than 30 seconds, shut it off immediately and re-prime.
Check for Equipment Leaks
With the pump running, walk the entire equipment pad and look for drips or spraying water. Check the pump lid o-ring — it often dries out over winter and needs a light coat of o-ring lubricant or replacement. A small leak at startup becomes a big problem mid-season.
Brush and Vacuum the Pool
Before adding any chemicals, brush the entire pool — walls, floor, steps, and corners. This loosens algae and dirt so the filter can capture it. Then vacuum to waste or to filter depending on how much debris is on the bottom. If there's heavy sediment, vacuum to waste to avoid overloading your filter.
Test Your Water Before Adding Anything
This is the most skipped step — and the most important. Take a water sample from elbow depth in the middle of the pool and test for: pH, Total Alkalinity, Free Chlorine, Calcium Hardness, and CYA/Stabilizer. Don't guess. Every pool comes out of winter differently.
🧪 Enter your test readings into PoolDiag and get exact chemical doses — no math required.
Get My Doses →Balance Alkalinity First
Get Total Alkalinity into the 80–120 ppm range before touching anything else. Add sodium bicarbonate to raise it, or muriatic acid to lower it. This is your foundation — adjusting pH on out-of-range alkalinity is like building on sand.
Adjust pH
Once alkalinity is in range, bring pH to 7.4–7.6. Use soda ash (pH Up) to raise it or muriatic acid / dry acid to lower it. Pre-dissolve granular chemicals in a bucket of pool water first, then pour slowly around the perimeter with the pump running.
Adjust Calcium Hardness
Target 200–400 ppm. Add calcium chloride to raise it. If it's too high, the only fix is partial draining and refilling. Plaster pools are especially vulnerable to low calcium hardness — it causes surface etching.
Perform Opening Shock Treatment
With the water balanced, shock with calcium hypochlorite (cal-hypo) at 1 lb per 10,000 gallons for clear-looking water. If the water is cloudy or greenish, double or triple the dose. Add shock at dusk or evening, distribute around the pool perimeter, and run the pump overnight.
Add Stabilizer (CYA) if Needed
If your cyanuric acid level is below 30 ppm, add stabilizer/conditioner to bring it to 30–50 ppm. Add through the skimmer slowly with the pump running. CYA takes 24–48 hours to fully dissolve — don't retest immediately.
Run the Filter and Re-Test After 24 Hours
Run the filter continuously for the first 24–48 hours. Backwash or clean the filter after the first run. Re-test the water after 24 hours and make final adjustments. Once chlorine is in the 2–4 ppm range, pH is 7.4–7.6, and the water is clear — you're ready to swim.
You're Open — Now Stay Ahead of It
The easiest way to keep your pool problem-free all summer is to test consistently (2–3 times per week), maintain chlorine above 2 ppm, and address imbalances before they spiral. An ounce of prevention is worth a pound of algaecide.