How To Open Your Inground Pool: 6 Steps To Crystal Clear Water

Introduction

Hey there, I'm Justin, your resident pool aficionado. And today, I'm talking about opening your inground swimming pool. A lot of people get confused about how to do this — but opening your pool doesn't have to be hard. And that's why I'm here to help.

It is a sequence. You can't do it in any random order. Most pool owners skip steps, do things out of order, or dump chemicals in before the water is circulating — then wonder why they're still fighting cloudy water three weeks into pool season.

Here's the thing: follow these 6 steps in order and you'll be swimming in no time. Skip around and you'll still be fighting a green swamp into June.

What You Need

Get everything together before you pull the cover. You won't want to be running back and forth to the pool store. So I made an easy checklist for you to follow. You can find all the links in the description below:

Water Testing Equipment

• Smart Water Monitor — this is your primary testing tool. You want one that is ORP-based, because ORP tells you how effective your sanitizer actually is—not just how much chlorine is in the water. Two pools can have the same chlorine level but completely different ORP, which means one is clean and one isn't. We use the ICO in our test pool, which continuously tracks ORP and pH every hour and pushes alerts directly to your phone so you're not guessing or reacting too late. I have a full review on it if you want to check it out. Or you can learn more at mysmartpool.com

• Handheld digital ORP meter — your second option if you prefer a manual approach. It still gives you accurate ORP readings so you know how well your sanitizer is working, but you'll need to test it yourself regularly instead of having continuous monitoring

• Taylor K-2005 liquid test kit — use this as a backup for alkalinity, calcium hardness, and CYA readings that your ORP sensor or smart monitor doesn't cover

  

Cleaning Tools

• Leaf net, pool brush, and a pool pole
• Manual vacuum or robotic cleaner
• Submersible pump — if you have a solid cover sitting in standing water

Equipment Pad Supplies

• Silicone-based O-ring lubricant — never petroleum. Petroleum destroys rubber seals.
• PTFE/Teflon tape for threaded fittings
• Spare O-rings for pump and filter lids
• Replacement skimmer and pump baskets if yours are cracked or warped
• Fresh pressure gauge if yours is fogged or cracked

Chemicals

• Liquid chlorine (12% sodium hypochlorite)

• pH decreaser (muriatic acid) and pH increaser (soda ash)

• Alkalinity increaser (sodium bicarbonate)

• Calcium hardness increaser (calcium chloride)

• Trichlor tablets

  

Step 1: Remove Cover

If you have a solid cover, pump off standing water first. Don't drag the cover across the pool — you'll dump months of accumulated leaves and debris straight in.

Remove the cover carefully, rinse it off, let it dry fully, and store it folded in a dry place. Storing a wet cover invites mold and shortens its life significantly.

Some debris will fall in no matter how careful you are. Accept it — you'll deal with it in Step 5.

Step 2: Fill Your Pool

Bring the water level to mid-skimmer before starting any equipment. Low water starves the skimmer, pulls air into the system, and risks running the pump dry — which can damage your pump and seals.

Step 3: Reconnect

Before touching anything electrical: test your GFCI. Pool pump circuits sit dormant all winter and outdoor outlets can corrode without any visible warning. Press TEST — circuit should cut. Press RESET — power should restore. If it won't reset or trips immediately when the pump starts, stop and call an electrician. A tripping GFCI is telling you something is wrong. Take it seriously.

Now reinstall everything you pulled last fall: return eyeballs, skimmer baskets, ladder and handrail plugs, pump drain plugs, filter drain plugs. If you winterized with expansion plugs in the returns or gizmos in the skimmers, swap them out now. Physically touch every fitting before starting the pump — one missed plug means a geyser later.

Inspect O-rings and lid gaskets. Cracked, flattened, or chalky means replace. Good ones get a coat of silicone lubricant before reassembly.

Prime and start the pump: fill the strainer pot with water, open suction and discharge valves, open the air relief valve on top of the filter tank, start the pump, and close the air relief only after a steady stream of water — not air — shoots out. Trapped air causes pressure buildup and prevents proper priming. Don't skip this valve.

If the pump doesn't prime within a couple of minutes, shut it down. Don't let it run dry.

Filter Reconnect By Type

Sand: Backwash 2 minutes → Rinse 30–60 seconds → Filter. Always shut the pump off before rotating the multiport valve. If the pool came out of winter green, use a sand filter cleaner additive during that first backwash — fouled sand develops channels where water bypasses filtration entirely.

Cartridge: Remove and hose off pleats inside and out. If the pool was rough last season, start with a chemically soaked or brand new cartridge. Body oils and sunscreen don't rinse out — they clog the media and kill flow rate. Reassemble with silicone on the O-ring.

D.E.: Start up, then add D.E. slurry through the skimmer within the first couple of minutes. Running without D.E. damages grids fast. Precoat is roughly 1 lb per 10 sq ft of filter area.

Step 4: Test — And Why ORP Changes Everything

Here's where most pool owners are still doing it wrong — and I want to fix that.

The standard advice is: test your chlorine. But here's the problem. Your chlorine level can be perfectly high and your water can still have zero sanitizing power. How? Because pH and CYA are chlorine's kryptonite. The wrong pH or too much CYA renders chlorine completely ineffective — it's just sitting there doing nothing. You'd never know that from a chlorine test.

This is why I monitor ORP — Oxidation-Reduction Potential. ORP doesn't measure how much chlorine is in the water. It measures whether that chlorine is actually working. It's a direct measurement of your water's sanitizing power, in millivolts. If your ORP is above 650 mV, your pool is actively killing bacteria and algae. If it's below 650, things are getting questionable. Below 600? You've got a problem.

This isn't some backyard experiment. Olympic facilities and commercial aquatic centers worldwide rely on ORP monitoring — not chlorine test kits. The reason most backyard pool owners have never heard of it is because traditional test strips aren't designed to measure it, and the pool store business model depends on you staying confused.

ORP is the one number to rule them all. Everything else — pH, alkalinity, CYA, chlorine — those are the inputs that drive your ORP. Nail your ORP and your water is genuinely safe.

The tool I use to monitor ORP is the ICO Smart Monitor by Ondilo. It sits in my pool, measures ORP and pH once an hour, and sends the data straight to my phone. No test strips, no color charts, no guessing. When ORP starts dropping, I know immediately — before it becomes a green pool problem. I have a full review of the ICO on the channel, and you can check it out at mysmartpool.com.

Now — run a full baseline test before adding anything. The order you adjust chemistry matters. Total Alkalinity is the anchor. Get it right first and pH becomes much easier to hold. Fix pH before worrying about chlorine — and watch your ORP respond once pH is dialed in.

Your primary ORP target: 650–700 mV

Parameter	Target	Why It Matters
ORP (Sanitizing Power)	650–700 mV	The number that actually tells you your water is safe. This is your primary target.
pH	7.0–7.2	The biggest driver of ORP. A half-point pH rise cuts chlorine power by 50%. Fix pH and ORP climbs.
Total Alkalinity (TA)	80–120 ppm	The anchor for pH stability — fix this first or pH will keep swinging.
Calcium Hardness (CH)	175–225 ppm (vinyl/fiber) / 200–400 ppm (plaster)	Too low and water leaches plasticizers from vinyl liners, making them brittle.
CYA (Stabilizer)	30–50 ppm	Sunscreen for your chlorine. Too much and chlorine gets locked up — ORP tanks.
Free Chlorine (FC)	2–4 ppm	The chemical doing the work. Dial this in last — ORP confirms it's actually working.

Need exact dosing amounts? Use my pool chemical calculator to plug in your current readings and pool volume — it tells you exactly what to add. I also have dedicated calculators for pH, alkalinity, and muriatic acid.

A few critical callouts:

• pH above 7.4: your chlorine is losing serious power. At pH 8.0, you're down to roughly 20% effectiveness. This is exactly why your ORP will be tanked even if your chlorine test looks fine. Fix pH first — always. Check out my guide on How to Lower Pool pH if you need help.

• Calcium Hardness below 175 ppm in a vinyl pool: water gets chemically hungry and leaches plasticizers from the liner, making it brittle over time.

• CYA above 80 ppm: chlorine gets so locked up it barely sanitizes — and your ORP will show it, even if free chlorine reads high. Trichlor tablet users, test this before adding any stabilizer. If CYA is already high, partial drain and dilute is the only fix.

  

Dosage Reference — Scale Linearly By Pool Volume

Goal	10k gal	15k gal	20k gal	25k gal	30k gal
Raise FC by 10 ppm — 12% liquid chlorine	3.3 qt	4.95 qt	6.6 qt	8.25 qt	9.9 qt
Raise FC by 10 ppm — 67% cal-hypo	13 oz	19.5 oz	26 oz	32.5 oz	39 oz
Raise TA by 10 ppm — sodium bicarbonate	1.4 lb	2.1 lb	2.8 lb	3.5 lb	4.2 lb
Raise CH by 10 ppm — 77% calcium chloride	1.2 lb	1.8 lb	2.4 lb	3.0 lb	3.6 lb
Raise CYA by 10 ppm — cyanuric acid	13 oz	19.5 oz	26 oz	32.5 oz	39 oz
Lower TA by 10 ppm — 31.4% muriatic acid	26 fl oz	39 fl oz	52 fl oz	65 fl oz	78 fl oz

Dose in stages — especially with acid. Circulate and retest before adding more. Watch your ORP come up as you get pH into range. If you don't know your exact pool volume, run it through my pool volume calculator first — every dosage depends on it.

Step 5: Clean & Filter

With the pump running and chemistry adjusted, now you physically clean. Net out everything visible first. Don't vacuum yet if the water is still cloudy — you'll blast debris back up and load the filter instantly.

Brush walls and floor to knock settled debris into suspension. Let the filter run. Backwash or clean when pressure rises 6–10 psi above your clean baseline — and expect to do it at least twice during the opening clear-up.

Aim your return jets downward and angled to one side to create a slow whirlpool effect that pushes debris toward the drain. If there's a dead spot in your pool where debris always settles, adjusting that eyeball fitting fixes it.

Run the pump 24 hours a day until the water clears. Once you've got clear water holding, dial back to your normal schedule.

Step 6: Shock

Shock last — after chemistry is in range and the filter is clean. Shocking into a dirty filter or a pool with pH out of range wastes product and time. If you want a deep dive on shocking, check out my full guide on How To Shock Your Pool. Or use my pool shock calculator to get the exact dose for your pool size.

And here's the thing about knowing when to shock: stop guessing. If you're monitoring ORP with your ICO, this becomes obvious. ORP under 650 mV? Time to shock. ORP under 600 mV? Shock heavily and immediately. That's the professional standard — and now you have access to it.

If you don't have an ORP monitor yet, the traditional triggers still apply: water is green or cloudy, combined chlorine is elevated, or you just want a hard oxidation reset after winter. If the water looks clear and chemistry tested clean, a normal chlorine dose to bring FC into the 2–4 ppm range is often enough.

Shock in the evening. UV burns off unstabilized chlorine fast — morning shocking is money down the drain.

Add liquid chlorine near a return jet while the pump is running. Walk the perimeter as you pour for even distribution. Run the pump overnight and test ORP in the morning.

Wait until FC drops below 5 ppm before swimming — typically 8–24 hours depending on how much you added.

That's It

6 steps, in order. Cover off, water level right, everything reconnected, chemistry tested and adjusted with ORP as your guide, filter running clean, then shock when ORP tells you to. Do it in that sequence and you'll have clear water while your neighbors are still pulling their covers.

For the best deals on smart monitors like the ICO and robotic cleaners like the Dolphin Premier or Sigma, head to ThePoolNerd.com/deals. Questions? Drop them in the comments. Enjoy that pool.

Frequently Asked Questions

What month should I open my pool?

You should open your pool before water temps hit 60°F.

• South (Texas, etc.): March–April
• Most of U.S.: April–May

The exact month doesn't matter nearly as much as temperature. Algae starts growing fast once water gets above ~60°F. If you wait too long, you're not opening a pool — you're fixing a problem.

Pool Nerd tip: Opening early is the single easiest way to save money and time all season.

What temperature should I open my pool at?

Around 55–60°F water temperature.

• Below 60°F → algae is mostly dormant
• Above 60°F → algae starts growing quickly

If you open at 70°F+, expect more chemicals, more brushing, and more frustration.

How long does it take to open a pool?

Hands-on time: 2–6 hours | Total time to clear: 1–7 days

Typical timeline:

• Day 1 → equipment + circulation
• Day 2–3 → chemistry adjustment
• Day 3–7 → filter clears water

Opening is quick. Clearing is what takes time.

What chemicals do you need to open a pool?

Core chemicals:

• Liquid chlorine (preferred over granular)
• pH decreaser (muriatic acid)
• Alkalinity increaser (sodium bicarbonate)

Depending on your water:

• Stabilizer (CYA) if low
• Calcium hardness (plaster pools)

What order should I add pool chemicals when opening?

This is where most people mess up. Correct order:

1. Get pump running
2. Test water
3. Adjust Total Alkalinity
4. Adjust pH — watch your ORP climb as you hit the 7.0–7.2 range
5. Add chlorine
6. Add stabilizer (if needed)

Rule: Always fix pH before dumping chlorine. Your ORP will confirm when you've got it right.

Do I need to shock my pool when opening it?

Not always. Let your ORP reading guide you.

Shock if:

• ORP is below 650 mV
• Water is green or cloudy
• High combined chlorine
• Lots of debris went in over winter

Skip shock if:

• ORP is above 650 mV and water is clear
• Chemistry is already close

Pool Nerd truth: Shock is just concentrated chlorine. Don't overthink it — and don't add it blindly. Let your ORP tell you when.

How much shock do I need to open a pool?

Target about 10 ppm chlorine.

• 10,000 gallons → ~1 gallon liquid chlorine
• 20,000 gallons → ~2 gallons
• 25,000 gallons → ~2.5 gallons

My pool shock calculator will give you the exact amount based on your pool size and current chlorine level. If your pool is green and ORP is tanked, you'll likely need more over several days. Monitor ORP and keep dosing until you're above 650 mV and holding.

Should I run my pool pump continuously after opening?

Yes — at least at first. Run 24/7 for the first 2–3 days. After that, you can dial it back. Your filter is doing the real work of clearing the pool.

How long does it take a pool to clear up after opening?

• Clear water → 1–2 days
• Cloudy → 2–4 days
• Green → 3–7 days

Chemicals kill algae. The filter removes it. ORP tells you when the job is actually done.

Why is my pool still cloudy after opening?

Common causes:

• Filter is dirty or undersized
• Not running pump long enough
• Low chlorine — confirmed by low ORP
• pH out of range — kills chlorine effectiveness and tanks ORP

Fix:

1. Get pH into the 7.0–7.2 range first
2. Clean/backwash filter
3. Run pump longer
4. Maintain chlorine and watch ORP climb

For more help, check out my full guide on How to Clear Cloudy Pool Water.

Why is my pool green after opening?

Almost always: opened too late, not enough chlorine, or poor circulation.

Fix:

1. Get pH right — then add chlorine aggressively
2. Brush daily
3. Run pump nonstop
4. Monitor ORP — you're aiming for above 650 mV and holding

For a full walkthrough, see my guide on How to Clean a Green Swimming Pool.

Do I need to add algaecide when opening my pool?

No. It's optional and most pros don't bother. Chlorine is the best algaecide ever invented. Keep your ORP above 650 mV and algae doesn't stand a chance.

Do I need to backwash my filter when opening?

• Sand → Yes (backwash + rinse)
• DE → Yes (and recharge DE)
• Cartridge → No (clean instead)

How often should I clean my filter when opening my pool?

More than usual. Expect to clean/backwash every 1–3 days if the pool is dirty. A dirty pool means the filter clogs fast.

Should I vacuum my pool before or after adding chemicals?

Remove debris before adding chemicals so you don't waste them.

How full should my pool be before turning on the pump?

Water should be at mid-skimmer level. Too low → pump sucks air. Too high → skimmer doesn't work properly.

Can I swim right after opening my pool?

Only if ORP is above 650 mV, water is clear, free chlorine is 1–4 ppm, and pH is in range. If you can't confirm all of those — wait.

What happens if I open my pool too late?

• Green water
• Higher chemical cost
• Longer cleanup time

What happens if I open my pool too early?

Not much. Slightly higher heating cost. Better early than late — every time.

How much does it cost to open an inground pool?

• DIY: ~$50–$150
• Professional: ~$200–$500+

Can I open my pool myself or should I hire a professional?

DIY if you understand your equipment and the pool is in decent shape. Hire someone if it's your first time, you've got equipment issues, or the pool is very dirty.

Why won't my pool pump prime after opening?

Common causes:

• Low water level
• Air leak
• Clogged basket
• Closed valve

Why is my pool filter pressure high after opening?

Filter is dirty — lots of debris in the water. Solution: clean or backwash the filter.

Do I need to add stabilizer (CYA) when opening my pool?

Only if it's low. Target 30–50 ppm. Important: if CYA climbs above 80 ppm, your ORP will tank even with plenty of chlorine — the CYA locks up the chlorine. Trichlor users, test before adding any stabilizer.

How do I know if my pool water is safe to swim in?

The real answer: check your ORP. Above 650 mV, your water is actively sanitizing. Combined with clear water and a pH of 7.0–7.2, you're good to go. If you're using a traditional test kit, target free chlorine 1–4 ppm, pH 7.0–7.2, and clear water.

What is the ideal pool chemistry after opening?

• ORP: 650–700 mV (your primary target)
• pH: 7.0–7.2
• Total Alkalinity: 80–120 ppm
• CYA: 30–50 ppm
• Free Chlorine: 2–4 ppm
• Calcium Hardness: 175–225 ppm (vinyl/fiberglass), 200–400 ppm (plaster)

How do I calculate how many gallons my pool holds?

Basic formula (rectangle): Length × Width × Average Depth × 7.5

For round, oval, kidney, or L-shaped pools, use my pool volume calculator — it handles all common shapes and gives you an accurate gallon count instantly.

What's the fastest way to clear a green pool?

1. Get pH into the 7.0–7.2 range first — otherwise the chlorine you're about to add is wasted
2. Add chlorine aggressively — aim for ORP above 650 mV and hold it there
3. Brush daily
4. Run pump 24/7
5. Clean filter often — expect multiple backwashes

Should I use liquid chlorine or shock bags?

Liquid chlorine. It works faster, it's cleaner, and it's more predictable. Shock bags are convenient but often overpriced and harder to dose accurately.

How often should I test my pool water during opening week?

If you have an ICO: your ORP and pH are being checked every hour automatically. You'll know the moment something shifts without lifting a finger.

If you're using a test kit: test daily during opening week, sometimes twice. Focus on pH first — then add chlorine and watch chlorine do its job.

The information is for educational purposes only. Handling pool chemicals, specifically muriatic acid and chlorine, involves significant risk of injury or property damage. Always read the manufacturer's labels and MSDS sheets. Use this information at your own risk.

If you want to look into a pool water monitor like the ICO, head on over to my deals page, where I post all the best deals on top pool equipment and more.