Opening your pool in spring is what sets up the whole season. Do it right and you get crystal-clear, safe water within days. Wait too long and you're fighting algae before you've even had your first swim.
Timing matters: open when daytime temperatures start consistently climbing (roughly 70°F and up). Warm water plus a neglected pool is exactly what algae needs to take over, so it's better to open a little early than a little late. Here's the step-by-step.
Open once daytime temperatures are reliably around 70°F (21°C) or higher. It's tempting to wait for peak summer, but opening in late May or June once it's already warm gives algae and other organics a head start, especially under a mesh cover where sunlight reaches the water. Opening earlier, while it's still cool, keeps you ahead of the algae.
Work through these in order. The whole process is usually a couple of hours of hands-on work, plus a day or two of running the filter until the water clears.
Not sure how much shock or balancing chemicals to add? Enter your pool volume and readings below for exact amounts.
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Best All-in-One Start-Up Kit
A pre-measured opening kit that takes the guesswork out of start-up. Includes algaecide, water clarifier, chlorine shock, and oil absorbers, everything you need to go from covered to clear.
Best Quick Test Kit
Fast diagnostic strips that read the key levels in about 15 seconds, pH, total alkalinity, hardness, and cyanuric acid, so you know exactly what to correct at opening.
Best Opening Shock
A high-strength, fast-dissolving cal-hypo shock that clears cloudy water and kills organics without adding extra cyanuric acid, ideal for a strong opening shock.
When daytime temperatures stay consistently around 70°F (21°C) or above. Opening earlier, while it's cool, keeps you ahead of algae; waiting until it's hot lets algae get established first.
No. Just top off the level and balance the existing water. Draining a hard-sided pool risks structural damage, and it's unnecessary, chemistry will clear even a green opening.
That's a normal algae bloom from sitting all winter. Follow a green-to-clean routine, balance pH, shock hard, brush, and run the filter until it clears. See our green-to-clean guide for the full process.
Usually a day or two. After shocking, let free chlorine fall back to 1–4 ppm and confirm pH is 7.2–7.6 and the water is clear before anyone gets in.
Open your pool as soon as the weather warms up, not once it's already hot. Pump off and store the cover, top off the water, reconnect and prime the filter, then balance and shock. Run the filter until it's clear, and you'll start the season with safe, sparkling water instead of a green mess.