Score
Ondilo ICO — Our verdict
The ICO is the easiest way to keep track of your pool water and handle it yourself. Hourly pH, ORP, and temperature readings straight to my phone, dosing advice sized to my actual pool, and one battery charge since February that's still at 23% in July — water chemistry went from a weekly guessing game to a set-and-forget system. I'll never go back to strips.
The good
- Hourly pH, ORP, and temperature readings pushed straight to your phone
- Connects directly to home Wi-Fi — no hub, dongle, or subscription fees
- Dosing recommendations sized to your actual pool volume and chemicals
- One battery charge since February — still at 23% in mid-July
- Replaceable plug-and-play probes instead of a disposable device
- Caught pH drift days before my water would have told me visually
The not-so-good
- Reads ORP (disinfection power), not a direct chlorine ppm number
- Probes need periodic calibration and eventual replacement
Ondilo ICO — key specs
| Measurements | pH, ORP/Redox (disinfection), water temperature — hourly; TDS on the salt version |
|---|---|
| Ideal ranges | pH 7.2–7.6 · ORP 650–750 mV · TDS 3,000–5,000 ppm (salt pools) |
| Connectivity | Wi-Fi 802.11 b/g/n (2.4 GHz) + Bluetooth Low Energy — no hub required |
| Battery | Rechargeable lithium-ion (USB) — my one charge in February is at 23% in mid-July |
| Build | UV- and chemical-resistant ABS, IP68 waterproof, rigid probe shell |
| Probes | Plug-and-play, removable, and replaceable; calibration kit included |
| App | iOS and Android, free, no subscription; trends by day/week/month |
| Smart home | Home Assistant support |
I've automated almost everything about my pool at this point. A Clear UV robot scrubs the floor and walls on a schedule, a skimmer handles the surface, and after four years my old Dolphin Premier taught me that "set it and forget it" isn't a marketing slogan — it's a standard. But there was one job I was still doing by hand every week like it was 1995: dunking a test strip, squinting at the color chart in the sun, and guessing whether that pink was "7.2 pink" or "7.8 pink."
The Ondilo ICO is the gadget that finally closed that loop. It's a floating smart water monitor that sits in the pool 24/7, samples the water every hour, and sends the readings to my phone. After more than a year with it bobbing around out there, I can tell you exactly what it does well and where it falls short.
What the ICO Actually Is
The ICO looks like an oversized chlorine floater, but the business end is underwater. The white cone hanging below the surface houses removable plug-and-play probes that measure three things every hour:
- pH — the acidity/alkalinity balance of your water. The app targets the classic 7.2–7.6 window.
- ORP (Redox) — the actual disinfecting power of your water, measured in millivolts, with an ideal range of roughly 650–750 mV.
- Water temperature — which matters more than people think, because warm water burns through sanitizer faster and grows algae quicker.
If you have a saltwater pool, the salt version adds a third probe for TDS (salinity), targeting the 3,000–5,000 ppm range. Mine is a chlorine pool, so I tested the standard two-probe unit.
The body is chemical- and UV-resistant ABS, it's IP68 waterproof, and there's no base station or dongle to plug in anywhere — it talks directly to your 2.4 GHz home Wi-Fi and falls back to Bluetooth when you're standing next to the pool. Crucially, there's also no subscription. You buy the device, you download the free app, and that's the whole business relationship.
Setup and Calibration
Setup took me about twenty minutes, and most of that was the probes, not the electronics. The app walks you through pairing over Bluetooth, joining your Wi-Fi, and then building a profile of your pool: volume, in-ground or above-ground, chlorine or salt, and which treatment products you actually use. That profile matters — it's what turns raw readings into dosing advice later.
The probes ship dry and need to be conditioned and calibrated before the readings mean anything. The calibration kit is included, and the process is just dipping the probes in reference solutions and letting the app confirm. It's not hard, but don't skip it — my pH probe read a couple tenths high out of the box, and calibration pulled it right in line with my Taylor drop kit.
That Taylor kit was my referee for the first few months. Once calibrated, the ICO's pH readings stayed within about 0.1 of my manual tests — tighter than I can read a test strip.
Living With Hourly Data
Here's the thing nobody tells you about testing your water once a week: you're not really maintaining chemistry, you're doing archaeology. By the time a strip shows you a problem, the problem is already days old.
The ICO flips that. Every hour, a new reading lands in the app, and the dashboard shows you trends by day, week, or month. Watching that data for over a year changed how I understand my own pool:
- Rain events show up instantly. A big summer storm would knock my pH and my ORP down within hours, and the app would flag it before the water looked any different.
- Heat waves are sanitizer killers. When water temp climbed into the 90s during a Texas July, I could watch the ORP sag day after day as the heat chewed through chlorine.
- Pool parties are measurable. A weekend with six kids in the water shows up as a very obvious dip in disinfection power. The ICO had me dosing that same evening instead of discovering cloudy water on Wednesday.
The app doesn't just show numbers — it tells you what to do about them. Because it knows my pool's volume and my exact treatment products, the recommendations come out as real-world instructions: add this much of this product, then re-check. It also folds in the weather forecast to anticipate swings before they happen. I stopped doing chemistry math entirely.
The ORP Question
This is the most important thing to understand before buying, so I'm giving it its own section: the ICO does not give you a chlorine ppm number.
Instead it measures ORP — the oxidation-reduction potential of the water. ORP is the more telling measurement, because it reports how effectively your water is actually killing things right now, factoring in pH, stabilizer, and temperature all at once. Commercial pools are regulated on ORP for exactly this reason. A pool can have "2 ppm of chlorine" on a strip and still sanitize poorly if the pH is out of whack; ORP catches that, ppm doesn't.
But it takes recalibrating your brain. If you've spent years thinking in ppm, staring at "685 mV" feels foreign for the first few weeks. My advice: run your normal test kit alongside it for a month, watch how the two relate in your pool, and you'll quickly learn what your water's healthy ORP looks like. After that, the millivolt number becomes second nature — and more useful than a ppm reading ever was.
Battery, Build, and Connectivity
Ondilo's battery claim is "charge it once or twice a season." Mine has done better than that. In over a year of use, I've charged it exactly once — a top-up back in February — and now, in mid-July, after a full pool season of hourly readings, it's sitting at 23%. One charge covered fall, winter, spring, and most of the swim season. Charging is USB, like a phone. Compared to hauling a cordless pool robot out to charge every couple of days, this is a non-issue.
Build quality has held up well. Over a year of direct sun, chlorine, and the occasional bump against the wall from my Clear UV doing its rounds, and the housing still looks new. The probes live inside a rigid shell, so there's nothing fragile exposed. And because the probes are replaceable, a worn sensor in a couple of years means a cheap swap, not a new device — I appreciate any company that doesn't design its product to become e-waste.
Connectivity was refreshingly boring in the best way. The ICO talks straight to your 2.4 GHz home Wi-Fi — no hub, no dongle plugged into an outlet by the back door — and my readings have arrived reliably for over a year. One practical tip: it's a device floating at ground level in water, so make sure your Wi-Fi actually reaches the pool. If your pool sits at the far edge of your coverage, a mesh node near the back of the house keeps the hourly readings flowing in real time. Home Assistant support is a nice bonus for the smart-home crowd.
What It Won't Do
An honest list, because no review should read like a brochure:
- No alkalinity, calcium hardness, or CYA readings. You still need a drop kit for the slow-moving parameters a few times a season. The ICO covers the fast-moving daily chemistry, not the full panel.
- It won't dose anything. It tells you what to add; you still walk out there and add it. (I prefer that to trusting a machine to pump acid unsupervised.)
- It's a visible gadget in your pool. It's small and reasonably subtle, but it does live on the surface. You can toss it in the skimmer basket during parties.
Final Verdict
The ICO does for water chemistry what my robot did for vacuuming: it takes a recurring chore that depends on me remembering to do it, and turns it into a notification that only shows up when something actually needs attention. It's simply the easiest way I've found to keep track of your water and handle pool care yourself — no service, no guesswork, no chemistry degree.
And it earns its keep fast. Price it against a season of guesswork: the algae bloom you catch three days late, the shock treatments, the swim days lost to cloudy water. The ICO paid for its spot in my pool the first time it pinged me about a pH slide that I would never have caught mid-week — days before it would have become a visible, expensive problem.
If you're the person who tests faithfully with a Taylor kit twice a week and enjoys it, the ICO is a luxury. For everyone else — especially anyone who's already automated their cleaning with a robot and wants the chemistry side handled with the same set-and-forget philosophy — this is an easy recommendation. My test strips are in a drawer somewhere. I don't miss them.
