How to open a pool in spring

When to open

Leslie’s, the pool retailer, suggests opening once daytime highs have reached about 65–70°F for at least a week: the risk of a hard freeze has usually passed, and waiting much longer gives algae a head start as the water warms. Opening a little early and keeping chlorine up is easier than opening late to a green pool.

Step by step

1. Clear the cover. Pump or siphon the water off the top and sweep off leaves, then lift the cover off without tipping debris into the pool. Clean it and let it dry fully before storing it.
2. Unplug and reconnect. Remove the winterizing plugs from the returns and the skimmer winterizers. Hayward’s filter manual warns that plugs left in suction outlets are an entrapment hazard, so check every one is out. Put back the drain plugs in the pump, filter and heater, refit the filter’s drain cap, and reconnect any hoses on an above-ground pool.
3. Refill to the normal level — usually the middle of the skimmer opening. If you are not sure how much water went in, a hose meter tells you; how long to fill a 10,000 gallon pool with a garden hose gives an idea of the time.
4. Start the pump (prime it if needed), check for leaks at every fitting, and run it on high while you work. Set the filter valve back to filter.
5. Clean. Skim, brush and vacuum; backwash or clean the filter once the first load of debris has gone through it.
6. Test everything: free chlorine, pH, alkalinity, calcium, stabilizer (CYA) and, for a salt pool, salt.
7. Balance in order — alkalinity, then pH, then calcium, then stabilizer — with the pump running and time between each chemical. The order is explained in how to balance pool water.
8. Shock, at dusk, then keep chlorine at the right level for your stabilizer. Swim once chlorine is back down to what your product’s label allows.

The opening chemistry, worked out

Most opening jobs need some of the same doses. For a typical 10,000 gallon pool: how much stabilizer for a 10,000 gallon pool if CYA was lost to a drain or heavy rain, how much baking soda to raise alkalinity in a 10,000 gallon pool for low alkalinity after winter rain, and how much liquid chlorine to shock a 10,000 gallon pool for the opening shock. Salt pools usually need a top-up after winter overflow — the pool salt calculator works it from your test. Opening kits are sized by pool volume, which is one more reason to know your gallons: the pool volume calculator works it out.

If it opens green

A green or cloudy pool at opening is common, especially if the cover leaked or the pool was closed while the water was still warm. Use the same order the shock and balancing guides use:

1. Keep everyone out and test free chlorine, pH and stabilizer (CYA). Most strips have a CYA pad; a pool store will test it free.
2. Very high CYA? Drain first. Above about 80 ppm the shock level gets impractical, so partly drain and refill before buying chlorine — see how much water to drain to lower CYA.
3. Clear the debris — skim leaves, empty the baskets — and start the pump. Leave it running until the pool is clear.
4. If pH is above about 7.6, lower it first to about 7.4 with acid, run the pump a few hours and retest: chlorine works better at lower pH. Leave alkalinity, calcium and stabilizer for later. Never add acid and chlorine together.
5. At dusk, raise chlorine to the shock (SLAM) level — 40% of your CYA — usually with liquid chlorine. How much liquid chlorine to SLAM a pool works the first dose.
6. Hold it there. Test two or three times a day and top up what was used. Strips can’t read this high — use a FAS-DPD drop test kit (a drop-count chlorine test) or a pool store’s free water test. Brush daily and clean or backwash the filter as its pressure rises.
7. Stop when it is clear and chlorine drops no more than about 1 ppm overnight (the Trouble Free Pool method’s rough guide). Let chlorine fall back to your label’s swimming level, then balance alkalinity, calcium and stabilizer in the usual order.

The first shock dose for a typical green pool is worked through on how much liquid chlorine to SLAM a pool.

Above-ground pools

• Check the wall and liner before you fill: look for rust at the bottom track, bulges and liner pulled out of the coping.
• Reconnect the hoses and clamps between the skimmer, pump, filter and return, and refill the filter with sand only if you emptied it — the pool filter sand calculator lists the amount by model.
• Soft-sided and frame pools that were stored come out of storage and go through a new setup, including a level base; see the above-ground pool sand calculator.

Common mistakes

• Leaving a winter plug in a suction line. Check the skimmer and main drain lines before the pump runs.
• Adding everything at once. Leslie’s kit instructions say never to mix chemicals and to allow time between different chemicals; one chemical, pump running, retest.
• Chasing pH before alkalinity. Fix alkalinity first, or pH will drift back.
• Swimming the same day as the shock. Wait until chlorine is back within the label’s limit.

In autumn, the same steps run in reverse — see how to close (winterize) a pool.