PoolOwl

Opening & closing

Pool Opening Planner

Turn your first test of the season into an ordered start-up checklist with balancing and chlorine doses filled in.

What you'll need (3)
  • Your pool's volume in gallons
  • Free chlorine, CYA, pH and total alkalinity results after the pool has circulated
  • How the water looks (clear, cloudy or green)
Units
Your pool
Don't know it? Work it out in about a minute.
How does the water look?
Your test results

Test right before you start. If you can't test CYA, a pool store will usually do it free.

Example: 1.
Example: 40.
Example: 7.8.
Example: 90.
Doses are for liquid chlorine. Use the chlorine calculator for other products.

Your opening plan

Your result will appear here

Enter your pool size and test results to build a step-by-step plan with chemical amounts.

How the plan is built

The planner follows the usual start-up order: clean the cover off, restore the water level and equipment, circulate, then test and adjust. Chemical doses follow your readings:

  • Alkalinity is raised first if it’s below 60 ppm.
  • pH is moved into 7.4–7.6.
  • Chlorine is topped up to the high end of normal for clear water. For cloudy or green water, it’s raised to the shock level for your CYA and held there.

Green water

A green pool after winter means algae, and algae uses up chlorine as fast as you add it. One big dose doesn’t work. Holding the shock level does: retest several times a day, top up, brush, and clean the filter as it clogs. Keep everyone out until you can clearly see the main drain.

Don’t forget CYA

Winter rain and splash-out dilute stabilizer. If CYA comes back low, chlorine will burn off in the sun almost as fast as you add it. Check it at opening, and use the CYA calculator if it needs raising.

Assumptions and limitations

  • Chemical amounts assume liquid chlorine, 31.45% muriatic acid, soda ash and baking soda.
  • Cloudy and green pools need repeated chlorine doses over days; the planner gives the first dose.
  • Test after the pump has circulated for a few hours, or the readings may not represent the whole pool.

Common questions

What order do I add chemicals when opening a pool?

Alkalinity first (it steadies pH), then pH, then chlorine. Add one chemical at a time with the pump running, and give each time to circulate.

How long does it take to open a green pool?

Often several days to a week of holding chlorine at shock level, brushing and cleaning the filter. Very green pools with high CYA can take longer; partially replacing water can speed things up.

Should I test the water before starting the pump?

Get the pump running and let it circulate for a few hours first, so your sample represents the whole pool rather than the layer near the surface.

Sources and methodology references

  1. Home pool and hot tub water treatment and testing, US Centers for Disease Control and Prevention
  2. Pool School (opening and clearing a pool), Trouble Free Pool

Published October 2, 2026. Results are estimates. See how our calculators work.

Spotted a wrong result or an outdated source? Report a problem with this calculator.

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