If your pool’s pH is too high, the chlorine you’re pouring in can be up to 80 percent less effective. Eighty percent. You could be dumping jug after jug into the water and barely moving the needle — and most pool owners never know it’s happening, because they’re dipping a test strip once a week and guessing the rest of the time.
I don’t guess anymore. Two numbers run my entire pool now, and this little floating device watches both of them around the clock. Once I learned how to keep those two numbers in range, pool care went from a weekend chore to a quick check on my phone with my morning coffee.
Hey guys, I’m Ryan with ActuallyUsed, where we put the products to the test so you don’t have to. Today I’m walking you through exactly how I use the Ondilo ICO to maintain my pool — what it tracks, the two ranges I live by, and the simple weekly routine that keeps my water clear without turning my garage into a chemistry lab.
What the ICO Actually Tracks
Quick refresher if you’re new here: the ICO is a floating smart water monitor. You drop it in the pool, connect it to your Wi-Fi, and it samples your water every hour and sends the readings straight to the ICO app on your phone. No strips, no drops, no squinting at little color charts. We’ve been using ours for over a year now.
It tracks three things. (The saltwater version adds a fourth reading for salt levels, but if you’re on chlorine, these three are the whole game.)
ORP. That stands for oxidation-reduction potential — and it’s measured in millivolts. This is your sanitation number. Here’s the key: ORP is not telling you how much chlorine you dumped in. It’s telling you how hard your water is actually working to kill bacteria and algae. Chlorine you added and chlorine that’s doing its job are two very different things, and ORP measures the one that matters. In my opinion, it’s the single most useful number in pool care — it’s what commercial pools run on, and it’s the reading that let me retire my test strips.
pH. How acidic or basic your water is. And this is the part most people sleep on: pH isn’t just about comfort or cloudy water. pH controls how well your chlorine works. These two numbers are in a relationship, and pH is the one calling the shots. We’ll come back to that in a big way.
Temperature. No target to chase here, but it’s context. Warm water burns through sanitizer faster and gives algae a head start, so when summer peaks, expect to feed the pool a little more often.
A test strip tells you what your water looked like for one second on a Saturday. The ICO gives you a trend line — where your water is headed. In my experience, that difference is what turns pool care from reacting to problems into preventing them.
The Only Two Numbers You Need
Alright, here’s the entire cheat sheet. Two targets:
- ORP between 650 and 750 millivolts
- pH between 7.0 and 7.4
That’s it. Keep those two in range and the water stays clear, the chlorine does its job, and nobody comes out of the pool with red eyes.
Sounds easy, right?
Well… here’s the catch. Neither number stays put. pH naturally drifts upward over time — every splash, every water feature, every bit of aeration nudges it higher. And ORP fades fast. Sunlight eats it. Swimmers eat it. Leaves, rain, dust — all of it chips away at your sanitizing power every single day.
So the game isn’t hitting those numbers once. The game is keeping them there with the least possible effort. And after plenty of trial and error, here’s the system I’ve landed on.
Step One: Fix pH First — Everything Revolves Around It
Remember that stat from the top? When pH climbs too high, your chlorine can be up to 80 percent less effective. Adding chlorine to a high-pH pool is like flooring the gas with the parking brake on. You’re burning fuel and going nowhere.
That’s why pH is always step one. Before I add a single drop of chlorine, I check pH on the app. My sweet spot is 7.2. The workable window is 7.0 to 7.6, but I aim for 7.2 because it gives chlorine its best conditions and leaves me room for that inevitable upward drift.
Since pH almost always drifts up, the correction is bringing it down: a small dose of muriatic acid with the pump running, then let it circulate and recheck the app. Follow the label amounts for your pool size, and remember the golden rule of pool chemistry — add less than you think you need, recheck, then add more if you have to. You can always pour more in. You cannot un-pour it. (My guide on how to lower your pool’s pH covers the safety rules and dosing in detail.)
Step Two: Raise ORP With Liquid Chlorine
Once pH is sitting in that 7.0 to 7.6 window, now we raise the ORP. My tool of choice: liquid chlorine, if you can get it locally.
Why liquid? Because it’s about as close as you’ll get to chlorine and nothing else. No stabilizer baked in, no calcium, no binders or fillers. You pour it in, and the ORP responds — clean and fast.
For dosing, here’s my rule of thumb: I typically add about one jug for every 200 millivolts I need to raise. So if the app is showing 500 and I want to be around 700, that’s one jug — and then I watch the ORP climb over the next few hours.
Now, that ratio comes from my pool and my testing. Your pool’s size, sun exposure, and swimmer load will move that math around, so treat it as a starting point. Dose light, let the ICO confirm where you landed, and top up from there.
Step Three: Hold It Steady With CYA-Free Pucks
Liquid chlorine raises ORP. Pucks are what hold it there, so you’re not out pouring jugs every other day.
Whether you’ve got an inline chlorinator or just a simple floater, either one works. But here’s the detail that matters more than the hardware: use pucks without CYA.
Most standard pucks are stabilized, meaning every single puck adds cyanuric acid to your water. And CYA basically never leaves. It doesn’t evaporate, it doesn’t burn off — the only real way out is draining and replacing water. As it stacks up, it handcuffs your chlorine, and you’ll watch your ORP sag on the app even though you keep feeding pucks. It’s a treadmill, and it’s why so many pools end up chlorine-locked by August.
CYA-free pucks give you that slow, steady chlorine feed without the buildup, which keeps your ORP stable instead of sawtoothing up and down.
One quick safety note: never mix different puck types in the same chlorinator or floater. If you’re switching over, clean the feeder out completely first — different chlorine chemistries do not play nice together.
Step Four: Watch the App and Dial It In
From here, the routine is almost embarrassingly simple. A few mornings a week, I open the ICO app with my coffee and glance at the trends. pH creeping toward 7.6? Small shot of acid. ORP sliding toward 650? Time to top up.
And here’s the payoff: once you’ve dialed in your pool’s rhythm, you’ll find you’re adding things about once a week. That’s it. The ICO’s hourly readings and alerts do the watching — you just make small corrections before they become big ones.
Keeping an eye on that app is the whole system. The trend line will warn you days before the water ever looks off, and catching a drift early means a splash of acid instead of a weekend fighting an algae bloom.
Quick Reference: Ryan’s ICO Targets
| Reading | My Target | If It Drifts High | If It Drifts Low |
|---|---|---|---|
| ORP | 650-750 mV | Ease off additions — sun and swimmers will bring it down | Liquid chlorine — my rule of thumb is about 1 jug per 200 mV; dose light and recheck |
| pH | 7.2-7.4 | Small dose of muriatic acid, circulate, recheck the app | Ease off the acid — natural aeration nudges it back up |
| Temperature | No target — context only | Expect ORP to fall faster; check the app more often | Chlorine lasts longer; enjoy it |
The Bottom Line
So, does the ICO make owning a pool easy? Absolutely. Here’s my take.
The ICO doesn’t pour the chlorine for you — you’re still the one doing that. What it kills is the guessing. Before, pool care meant strips, squinting at little colored squares, and hoping. Now it’s two numbers on my phone. They’re either in range or they’re not, and if they’re not, I know the exact nudge to make.
Keep pH at 7.0 to 7.4 so your chlorine can actually work. Keep ORP at 650 to 750 — liquid chlorine to raise it, CYA-free pucks to hold it. Add less, recheck, add more if needed. And watch that app. It’s your early warning system.
That’s the whole method. In my experience, it’s the difference between owning a pool and the pool owning you.
If you want my full deep-dive on the ICO itself — setup, accuracy, and how it stacks up against the cartridge-based monitors — that review is right here. And I’ve got more water-chemistry-made-simple guides in the pool maintenance hub.
Thanks for watching — I’ll catch you on the next one.
