How to Raise CYA Without Destroying Your Pool Chemistry

You could be wasting over HALF your chlorine! And today, I’ll show you the $15 fix.

Every jug of chlorine you pour into an unprotected outdoor pool is on a timer. And I’ve seen it happen all the time — the chlorine reading looks fine on a strip, while your sanitizing power falls by the minute in the sun. The sun doesn’t care what you paid for that jug.

The fix is one cheap chemical: cyanuric acid. Stabilizer. Today I’m going to show you how to raise it the right way — because this is also the one chemical in pool care you can’t take back out. Get it right, and the fix costs fifteen bucks. Get it wrong, and the fix is a garden hose and a water bill.

Hey guys, I’m Ryan with ActuallyUsed, where we put the products to the test so you don’t have to. Today: what CYA actually does, the exact numbers to hit, how to dose it without overshooting, and why I don’t run chlorine pucks in my own pool on a weekly basis. Let’s get into it.

What CYA Actually Does

Cyanuric acid goes by a bunch of names — CYA, stabilizer, conditioner. Same chemical. Here’s the job. UV light from the sun tears chlorine apart, and it’s shockingly fast. An outdoor pool with zero stabilizer can burn through most of its free chlorine in a single sunny afternoon. Chlorine without CYA is ice on a driveway in July. Technically it’s out there working — just not for long.

CYA fixes that by loosely bonding with chlorine and shielding it from UV, then letting go a little at a time so the chlorine keeps sanitizing all day. Same amount of chlorine, several times the working life.

One carve-out before we go further: indoor pools. No sun means no UV, which means you don’t need this chemical at all. Zero to 20 ppm and you’re set — the rest of this guide is for the outdoor crowd.

The One-Way Door

Before we touch a single granule, here’s why I treat CYA differently than everything else on my shelf.

CYA is a one-way door. Adding it takes ten minutes. Removing it takes a hose, a water bill, and most of a weekend. There’s no chemical that reliably pulls stabilizer back out of the water — I’ve seen the reducer bottles at the pool store, and in my experience they don’t move the needle enough to matter. The only fix that actually works is draining a chunk of your pool and refilling with fresh water. And then you get to rebalance every other chemical from scratch. (If you’re already there, my guide on how to lower CYA walks through the safe way to do it.)

So every step in this guide is built around one idea: go slow. You can always add more tomorrow. You can’t easily add less.

The Numbers to Hit

So what are we aiming for? Depends on your pool. Standard outdoor chlorine pool: 30 to 50 ppm. Saltwater pool: 60 to 80. Indoor pool: zero to 20, and zero is fine.

Why do salt pools get a higher target? Because a salt cell generates chlorine with no stabilizer attached to it, all day long. If there isn’t enough CYA already in the water to protect that chlorine, the sun burns it off about as fast as the cell can make it — so the cell runs longer and harder just to hold the same reading. My theory, and I’ll flag it as a theory since I haven’t run a five-year cell test, is that you’re paying for that in cell lifespan. The cell is the most expensive part of a salt system. Sixty to 80 ppm is cheap insurance.

Test Twice, Dose Once

Rule number one: never dose CYA off a guess, and never off a single test. CYA is the squirreliest test in pool care. The standard method is a turbidity test — mix pool water with a reagent in a little tube and watch for a black dot on the bottom to disappear. Lighting, eyesight, the angle you hold it — all of it moves the result. Run it twice and average the two.

For gear, a Taylor drop kit like the K-2006 is what I trust for the actual number. Test strips are fine for a quick “am I roughly in the zone,” but I wouldn’t measure out chemicals based on a strip.

And here’s where my ICO water monitor earns its keep. It will not hand you a CYA number — no continuous monitor does that. What it gives you is ORP, around the clock: the actual killing power of your water, not just how much chlorine is floating in it. The target band is 650 to 750 millivolts. When stabilizer is low, you can watch ORP sag all afternoon while a strip swears your chlorine is fine. In my testing, that graph is the earliest warning you’ll ever get. It runs about 400 bucks, no subscription, and my full review is here on the site.

How to Raise It the Right Way

Alright — the actual how-to. What you want is pure cyanuric acid. It’s sold as “stabilizer” or “conditioner,” in granular form, and check the back of the bag: the only active ingredient should be cyanuric acid. Not tablets. Not stabilized shock. One chemical, one job. We’ll get to why that matters in a minute.

The math is simple: about 13 ounces of pure CYA raises 10,000 gallons by roughly 10 ppm. Know your gallons, do the math — here’s the cheat sheet. And here’s the rule I never break: raise it 10 ppm at a time. If you’re at 20 and want 40, that’s two doses on two separate days. Not one big scoop.

How it goes in matters too. Don’t dump granules straight into the skimmer, and don’t broadcast them across the pool. Undissolved acid sitting in your plumbing is asking for trouble, and on a vinyl liner, a pile of granules on the floor can bleach a spot you’ll be staring at for years. Here’s what I do instead: pour the measured dose into an old sock or a leg of pantyhose, knot it, and hang it right in front of a return jet so moving water works on it nonstop. Every few hours, throw on gloves and give it a squeeze to break up the clumps.

Then comes the hard part: waiting. CYA is one of the slowest-dissolving chemicals you will ever put in a pool. In warm summer water, give it a full 48 hours before you retest. In cold spring water, it can take most of a week to fully show up on a test. Which brings me to the number-one way people wreck their pool with this stuff.

Why I Don’t Recommend Pucks

Now, the pucks. Trichlor tablets in a floater. I know a lot of you run them, and I get the appeal — drop them in, walk away, chlorine handled for the week.

Here’s the part the label technically tells you but nobody reads: trichlor is two chemicals pressed into one puck. It’s chlorine plus stabilizer, bonded together, and you only get a vote on one of them. Every pound of trichlor that dissolves in a 10,000-gallon pool adds roughly 6 ppm of CYA — and that never pauses. The puck doesn’t know your stabilizer hit 50 back in June. It just keeps stacking more, tab after tab, all season long.

Run tabs as your primary chlorine from May through September and it’s completely normal to close the year over 100 ppm — double or triple the target. And up there, chlorine gets sluggish, algae starts winning fights it should lose, and the usual reaction is to shock the pool… often with dichlor granules, which also carry stabilizer. At that point you’re bailing out a boat while a hose fills it back up.

To be fair to the tab makers — nobody’s lying to you. It’s on the label, and tabs have a real place: vacation weeks, or pools with tons of splash-out and constant fresh fill. But as your everyday chlorine source? In my opinion, that’s buying a chemistry problem on a payment plan. My setup is liquid chlorine for daily sanitizing and pure CYA dosed once or twice a season. Two levers, moved separately. That’s the whole trick.

When to Raise CYA and When You Shouldn’t

Quick word on timing, because “my CYA tested low” doesn’t always mean “add stabilizer today.”

The moments low CYA actually shows up: spring opening — rain and snowmelt diluted your water all winter, so a low spring test is normal, not a crisis. After a big storm or heavy backwashing. After a partial drain — lose a quarter of your water, you lose a quarter of your stabilizer with it. And the sneaky one: the season after you switch from tabs to liquid chlorine. Those tabs were quietly topping off your CYA the whole time. Liquid doesn’t, so a year later people think something’s broken. Nothing’s broken — you just have to add stabilizer on purpose now.

And when to leave it alone: if you’re anywhere inside the target range and the pool is holding chlorine through the day, don’t chase a prettier number. If you dosed within the past week, wait — it may not have registered yet. And if you’re closing in a month, save the money. Winter doesn’t need stabilizer.

Clear Water Is Not Clean Water

One last trap before the wrap-up. Low CYA doesn’t make water look bad — not at first. The chlorine burns off, and the water just sits there sparkling like a screensaver. But a clear pool and a sanitized pool are two different tests. Once the killing power’s gone, everything you can’t see gets a two-day head start before the haze shows up — three before the green. This is exactly where an ORP graph pays for itself: the water looked identical on both days. The graph did not. (I dig into this in Your Pool Is Crystal Clear — But Is It Actually Safe to Swim?.)

Two quick notes on lowering the load in the first place. SpectraLight says their UV system kills 99.9 percent of pathogens before the water returns to the pool — that’s the manufacturer’s number, not my measurement — and less demand on your chlorine means less pressure on your stabilizer. Same logic with debris: a corded robot like my Dolphin Premier pulls leaves and organics out before they rot and drag your chemistry around. Everything in the water is connected.

My Final Thoughts

So what’s my final thoughts? Here’s the whole guide in 30 seconds.

Outdoor chlorine pool: 30 to 50 ppm. Salt pool: 60 to 80. Indoor: skip it. Test twice before you dose. Buy pure cyanuric acid — not tabs — sock it in front of a return jet, raise 10 ppm at a time, and wait two full days before retesting. A full week if the water’s cold. And keep an eye on ORP, not just chlorine, because clear water hides the truth.

CYA is the foundation everything else in your water sits on. Get it right once, move slow, and your chlorine finally sticks around long enough to earn its keep.

If this guide just saved you from a drain-and-refill, the other side of this coin is how to lower CYA when it’s already sky-high. My full ICO review and my top water monitor picks are here on the site, more pool care guides live in the pool maintenance hub, and I keep running deals on all my top gear on the deals page.

Thanks for watching — I’ll catch you on the next one.