How to Open a Pool in Spring (Without Buying a Start-Up Kit)

Pulling the cover off is the best part of spring — and how you do the next four hours decides whether you’re swimming next weekend or fighting algae for a month. The good news: the process is short, the chemical list is nearly empty, and the most valuable step costs nothing.

Open before the water reaches 60°F. That’s the whole trick. Algae grows much slower in cold water, so opening early greatly reduces your risk of a green pool. Waiting too long is one of the most common mistakes people make, and it’s what turns a two-hour opening into a two-week recovery.

Before you touch the cover

Fifteen minutes of prep here saves hours later:

• Clean the filter. Cartridge or DE gets cleaned now; sand can be backwashed once the system is running.
• Clear the debris off the cover — all of it.
• Pump off any standing water if you have a solid cover.
• Walk the equipment pad looking for leaks, cracks, and anything that needs replacing before you pressurize it.

Step 1: Take the cover off slowly

This step matters more than people realize. Rushing it dumps everything you just cleaned off the cover into the pool. Remove all the debris, drain the remaining water, then pull the cover carefully — it’s heavy when wet, so get help.

Two notes for the cover itself, since you’re about to store it for six months:

• Dry it before you store it or it will mildew. Spread it on the driveway, mop it with a dish-detergent solution, hose it off, and let it dry.
• If you ran a cover pump on a solid cover and the level kept dropping, check for pinholes — a pinholed cover lets the pump quietly drain your pool.

Step 2: Get the big debris out

Once it’s uncovered:

• Run a robot if you have one — it’s the fastest way to lift silt and dirt off the bottom before it clouds up. (Which robot suits which surface if you’re shopping.)
• Leaf rake or skimmer net for anything large.

Don’t try to get it perfect yet. You’ll vacuum properly once the pump is running.

Step 3: Reassemble the equipment

Pull the winter plugs — rubber ones last. This is the tip that saves a service call: if you have rubber expansion plugs, open those last, because the negative pressure in the pipe can suck a plug into the line once the system starts drawing.

Then put it all back together:

• Drain plugs and pump lid. Pentair’s SuperFlo VS instructions are just “reinstall the two drain plugs, hand tighten only” — the plugs you stored in the strainer basket last fall.
• Lube every o-ring with silicone lube. Only silicone. The wiki is emphatic: never use petroleum products such as Vaseline on anything rubber, use a lube that’s 100% silicone, and skip PTFE/Teflon, which gums up and gets sticky.
• Filter drain plugs, air relief valves, heater plugs all go back, lubed.
• Reinstall chlorinator covers, drains, and your salt cell.
• Ladders and handrails go back in.
• Check skimmers, returns, and hoses for freeze damage while everything is apart. This is the only time of year you’ll have a clear look.

A note on the antifreeze you put in last fall: you don’t need to pump it out. It is safe to let pool or marine antifreeze drain into the pool — chlorine will rapidly destroy the antifreeze compounds.

Step 4: Refill, prime, and start it up

Fill so the water is halfway up the skimmer opening. Pentair says the same in the SuperFlo VS manual: always maintain proper water level in your pool, halfway up the skimmer opening.

Then prime the pump before you hit the switch. Put water into the pump so the shaft seals aren’t running dry. Every manufacturer says a version of this, and it’s the fastest way to destroy an otherwise healthy pump:

• Pentair: do not run the pump dry — the shaft seal will be damaged.
• Hayward: fill the strainer housing with water to suction pipe level. Never operate the pump without water.
• Bestway (above-ground): do not dry run the filter pump — and the priming step has to be repeated every time you start the pump after winterizing.

Above-ground owners, take this one seriously: pumps designed for in-ground pools are self-priming; above-ground pool pumps often are not. If you flip the switch on a dry above-ground pump and walk away, you can cook it in minutes.

If you have a DE filter, don’t forget to add DE when you start the system — an empty DE grid filters nothing and gets dirty fast.

Sand filter startup: backwash for at least two minutes, then rinse, then go to filter. And always turn the pump off before changing valve positions — moving a multiport under pressure is how spider gaskets die.

Then let it circulate for 24 hours to mix the water. That’s the actual documented figure — not the “run it 72 hours straight” advice you’ll see repeated online. Once it’s circulating, vacuum the silt off the bottom.

Step 5: Chemistry — in this order

Here’s the part where the pool store makes its money and you don’t have to give it to them. Start-up kits usually include unnecessary products and overpriced chlorine. Test first, then add only what your pool actually needs — with a drop-based kit, not strips. (How to test your water covers the kit and the method; is the pool store a scam covers why their printout says you need eight bottles.)

Test FC, CC, CYA, pH, TA, CH, and salt if you have a salt system.

5a. Chlorine goes in first — the same day

Most pools open with zero chlorine, and zero chlorine is an algae invitation. Add liquid chlorine right away, up to the target FC for your CYA. Don’t wait until tomorrow, and don’t wait until you’ve “balanced everything first” — at a routine opening, chlorine is the urgent number.

• Target FC band (≈ 11–12% of CYA)
• Minimum FC (≈ 7.5% of CYA)
• Below minimum — algae can grow

5b. Raise CYA to about 30 ppm — then stop

Get CYA to roughly 30 ppm first, which protects the chlorine you just added from the spring sun. Use the sock method (CYA takes a day or more to dissolve). Then stop and run an overnight chlorine loss test before adding any more stabilizer.

5c. The OCLT — the step almost everyone skips

An overnight chlorine loss test is free, takes zero effort, and is the difference between a clean opening and a month of misery. Test FC at dusk, test again at first light, and compare. A loss of 1.0 ppm or less means no algae. If you fail the OCLT, or your combined chlorine is 1.0 or higher, you have something to kill — go run the SLAM process.

5d. The winter-CYA trap: ammonia

This is the one that ruins springs, and it’s genuinely counterintuitive.

You’ll read that “CYA degrades over the winter.” What actually happens is worse than degradation. CYA does not break down on its own. When your stabilizer reads near zero after a closed winter, it’s usually because bacteria ate it — and that can only happen once free chlorine has fallen to zero. Those bacteria convert your CYA into ammonia, which is a chlorine sink of a different order.

The signature is unmistakable once you know it: disappearing CYA, high combined chlorine, low pH, and an inability to hold a chlorine level at all.

The test: add enough liquid chlorine for 10 ppm and test free chlorine 30 minutes later. If you lost 80% or more, you likely have ammonia.

And here’s the part that matters most: if you have ammonia, you absolutely should not add any more CYA. Every instinct says “my stabilizer is at zero, add stabilizer” — and doing that while ammonia is present digs the hole deeper. Clear the ammonia with chlorine first (it takes a lot; keep adding until FC finally holds), then bring CYA up. And if your CYA is high rather than low, note that dilution is the only proven way to reduce it — see CYA too high.

5e. Then balance the rest

With chlorine established and the OCLT passed, bring pH, TA, and CH into range. The 5 numbers covers targets; water balance and LSI covers why they interact.

5f. Salt systems

If you have a salt pool:

1. Test salt with a proper salt test.
2. Add only two-thirds of the calculated amount. Overshooting is only correctable by draining water.
3. Circulate 24 hours, then retest and top off.
4. Turn the cell on last. Hayward’s manual is explicit: do not turn the Aqua Rite on until pool water chemistry has been brought to proper levels. And the cell may not run at all in cold water regardless — Pentair’s IntelliChlor cuts off at 52°F ±3°F, Hayward’s below 50°F. Practically: water above 60°F, salt correct, 24 hours circulated, then start it.

If you opened to green

Don’t panic and don’t drain the pool. A green opening is a chlorine problem, and draining creates a much bigger set of problems:

• Vinyl liner pools should not be drained below 12-18 inches of water in the shallow end.
• Fiberglass pools should not be drained at all without significant precautions — they can pop out of the ground.
• Above-ground pools are risky to drain because of the fragility of the walls and supports.
• In general, exchanging water is safer than draining it.

Instead, run the SLAM process. The short version: set pH to 7.2-7.5 before you start, raise FC to shock level — 40% of your CYA — with liquid chlorine, run the pump 24/7, brush, and hold that FC by retesting and re-dosing several times a day. You’re done when all three are true: combined chlorine at or below 0.5, overnight FC loss of 1.0 ppm or less, and the water is crystal clear. You can swim during a SLAM as long as you can see the bottom and FC is between your minimum and the SLAM level.

If the water is clear but something still feels off, green but levels look fine and cloudy water cover the near misses.

Above-ground opening specifics

Most of the sequence above applies, with these differences that actually matter:

• Reconnect the external plumbing first, then fill. Hoses, unions, and the return/skimmer fittings are all outside the pool on an above-ground, and every one of them is a leak candidate after a winter of cold. Reinstall with the spider gasket you stored indoors and lube it.
• Prime manually, every time. Above-ground pumps are frequently not self-priming, and Bestway specifically notes the priming procedure must be repeated at every startup after winterizing.
• Replace the cartridge, don’t resurrect it. Intex’s own manual says to discard the old cartridge and use a fresh one. A winter-stored cartridge is a false economy — see sand vs. cartridge for above-ground.
• Refill to halfway up the skimmer, same as in-ground — the skimmer needs the water line in the middle of its mouth to skim rather than gulp air.
• Inspect the wall and top rails before the water goes back up. This is your one clear look at them all year.
• Sand filter people: if you dumped the sand at closing, refill and level it before you prime, then backwash-rinse-filter. (Sand vs. glass vs. filter balls if you’re reconsidering the media.)

After it’s open

• Don’t backwash on a calendar. The only trigger is filter pressure 25% above your clean baseline. Backwashing early just wastes water and chemistry.
• Go back to a normal run schedule, not 24/7 — see why 24/7 is a myth.
• Set your summer CYA and FC targets — how chlorine and CYA work is the one concept that makes the rest of the season easy.
• Plan for the first trip away. Prepping your pool before vacation is the same runway math you just did, in miniature.

Bottom line: open early — before 60°F — clear the cover before you pull it, lube everything with silicone, pull the rubber plugs last, prime the pump before you start it, and put chlorine in the water the same day you uncover. Then test before you buy a thing. Get CYA to 30, run the overnight loss test, and if your stabilizer vanished over the winter, check for ammonia before you add more. That’s the whole job — and it’s the exact reverse of how to close a pool for winter.