How to open a pool

When to open

Earlier than you think. Open once daytime temperatures are regularly in the 70s, before the water warms up enough for algae to take off under the cover. An early opening is usually a clear pool and a little chlorine; a late one is often a green pool and a week of work.

Step 1: Take the cover off cleanly

1. Pump the water off the top of a solid cover first, and sweep or blow off leaves. Whatever is on the cover ends up in the pool if you rush this.
2. Remove the cover, clean it, let it dry fully, and fold it for storage. Storing a damp cover grows mildew.
3. On an above-ground pool, deflate and remove the air pillow.

Step 2: Get the water and equipment running

In-ground pools

1. Raise the water to the middle of the skimmer opening.
2. Remove the winterizing plugs from the returns, the Gizzmo from the skimmer, and any skimmer line plug. Put the return eyeballs back in.
3. Reinstall the equipment: drain plugs back in the pump and filter, the pressure gauge back on the filter, and the salt cell back in its union. Set a multiport valve back to Filter.
4. Open the valves, including the main drain valve you closed in fall.
5. Prime the pump: fill the pump basket with water, close the lid, and turn the power back on. Run it and check every fitting for leaks and for air in the pump basket.
6. If you used pool antifreeze, run the pump to waste or backwash for a few minutes to clear it out of the lines.

Above-ground pools

1. Remove the skimmer cover plate and the return plug, and top up the water to the middle of the skimmer.
2. Reconnect the pump and filter, put the drain plugs back, and reattach the hoses with their clamps.
3. Prime and start the pump, and check the hoses and fittings for leaks.

Step 3: Test everything, then balance

Run the pump for a few hours first so the water mixes, then do a full test, including CYA and calcium. Winter rain and snowmelt dilute everything, so expect CYA and calcium to be lower than when you closed, and don't assume last fall's numbers.

Fix things in this order:

1. Chlorine first if the water is green or cloudy (see Step 4). Algae uses up chlorine faster than anything else in the water.
2. CYA: bring it back to 30 to 50 (60 to 80 for salt pools). It sets how much chlorine you need, so get it right early. Stabilizer dissolves slowly, so allow a few days.
3. Alkalinity, then pH. Alkalinity first because it controls how pH moves; then bring pH into 7.2 to 7.8.
4. Calcium hardness: top it up if dilution took it low.
5. Salt pools: test salt and bring it to your cell's range before turning the cell back on. A cell run with low salt can be damaged.

Use the chlorine calculator to set your chlorine target from your CYA and work out how much to add.

Step 4: If it's green or cloudy

Very common after winter, and fixable. Don't drain it. SLAM the pool: hold chlorine at 40% of your CYA, run the pump 24 hours a day, brush daily, and keep going until combined chlorine is 0.5 or less, the water is clear, and you pass the overnight chlorine loss test. A swampy pool can take a week or more; a little cloudiness, a day or two.

Step 5: The first week

• Run the pump longer than normal, around the clock if the water is cloudy.
• Brush and vacuum every couple of days to lift settled debris into the filter.
• Watch filter pressure: it climbs as the filter catches winter's dirt. Clean it when pressure is about 25% above clean.
• Test chlorine daily until it holds steady, then go to your normal schedule.

Closing again in the fall? See how to close a pool.