WaterGuru Sense S2 review: Upgraded pool chemistry analyst

Best Prices Today: WaterGuru Sense S2

The WaterGuru Sense (now marketed as the Sense S1) changed the game for my swimming pool maintenance back in 2022. It drops a sensor into your skimmer basket, where it takes regular measurements of chlorine, pH, and temperature, letting you know if anything is getting out of balance; no test tubes required.

I liked the WaterGuru Sense S1 so much I’ve kept it installed ever since, continuing to purchase the consumables needed to keep the sensor data coming. The all-new WaterGuru Sense S2 doesn’t change much on the surface—the two units look nearly identical, in fact—but it measures additional chemical levels the original doesn’t.

WaterGuru Sense S2 feature set

Let’s dig into the new features. While the original Sense measures pH and free chlorine daily, the Sense S2 adds measurements of cyanuric acid (CYA), total alkalinity, and calcium hardness (or water hardness). The new Sense S2 is supposed to measure pump flow performance hourly instead of just once a day, although I can only find daily reporting of flow levels in the app. Water temperature measurements remain relayed once every 30 minutes, as they were on the original Sense. Finally, the Sense S2 is also suitable for use in hot tubs, while the original Sense is not.

I love the Sense and check its results carefully every day to see if we need to get ahead of a chemical situation

Why do these new readings matter? Let’s look at each.

CYA is a compound that keeps chlorine stable in the pool. Without it, chlorine breaks down due to ultraviolet radiation. If you don’t have enough CYA, your chlorine will vanish too quickly, but too much CYA can cause problems as well, reducing the effectiveness of chlorine and causing algae growth. It’s important to note that CYA can’t be removed from a pool short of draining it; so, overloading with CYA can be a big issue.

Total alkalinity is related to pH and is a measurement of pH level stability. I’ve seen it described as being to pH what CYA is to chlorine; in this case, it’s a measurement that indicates how resilient your pH level is.

Finally, there’s calcium hardness, which is familiar to anyone who lives with hard water. I live in central Texas, where the water seems to be more limestone than H2O, and the mineral clogs shower heads and leaves stains on all our countertops. Too much calcium can cause the same kind of deposits to appear in the pool, but too little can cause calcium to leech out from the plaster, weakening the material.

The fine print is that it’s not the Sense hardware itself that is making the chemical measurements but rather the replaceable cartridges that you put in the Sense periodically. But the cartridges can’t relay their readings to you without the hardware they reside in.

Water Guru Sense cartridges

There are two different cartridges for the Sense S2: the C5 and the C2. The C5, as the name suggests, measures all five chemical levels described above, but it only lasts one month. The C2 measures just pH and free chlorine, but it lasts two months (same as the C1 cartridge used with the Sense S1). Both cartridges effectively cost $20 each, being sold as a 3-pack of C5 cartridges for $60, or a $60 combo pack consisting of two C2 cartridges and one C5 cart. WaterGuru pushes the latter bundle pack regularly, suggesting perhaps that you don’t really need to measure CYA, alkalinity, and calcium hardness all that frequently.

My pool guy would probably agree; he measures total alkalinity and CYA but never calcium, and the only chemicals he ever uses to adjust anything in the pool are chlorine (solid and liquid) and muriatic acid. That said, he told me does keep tabs on those other numbers and manipulates them when required.

Is all this extra knowledge helpful to the layperson? One moderate problem I’ve noticed with the app is that it only reports the most recently recorded data point for each variable, but it includes that information in its push notifications as if it is a fresh recording every day. I sent a water sample to WaterGuru for manual testing a month ago (though this WaterGuru Test service appears to be unavailable going forward) and received back a report that noted low CYA and calcium in the pool.

My last C5 cartridge-based readings for those numbers date back to September 2023. But even though that measurement is now a month old as I write this, I am still instructed daily to, for example, add 63 cups of 90-percent concentration calcium chloride. I’m currently using a C2 cartridge, and had I in fact added those chemicals, WaterGuru wouldn’t be able to measure the results of the addition until I install a new C5 cartridge into the WaterSense. A less skeptical consumer in my shoes might be prone to keep adding more and more chemicals every day because they wouldn’t see any changes reported in the app, which could ultimately create a problem.

Prices have been going up, too. When I reviewed the original Sense in 2022, it was priced at just $199. The Sense S1 now costs $295 and the Sense S2 is priced at $325. Consumables used to cost $50 for three cartridges; they’re $60—and with the combo C5/C2 cartridge pack, you’re only getting 5 months of use instead of 6.

Should you buy a WaterGuru Sense?

I still love the Sense and check its results carefully every day to see if we need to get ahead of a chemical situation before our appointed pool maintenance day, but I doubt most pool owners will need to spend the extra money for the S2, at least not while the S1 remains available. At press time, prices were discounted to $292.50 and $265.50 respectively, but the model S1 was out of stock. If you do buy the Sense S2, I don’t think the more expensive C5 cartridges add a lot of value.

As a final note, I am happy to report that, while the hardware is functionally identical, some upgrades have clearly gone on to the Sense S2 under the hood. I experienced none of the setup issues with the Sense S2 that troubled me with the original Sense. Just pop in four C batteries, install a cartridge, and drop the sensor into the water. A quick Bluetooth connection had the device registered on my network within a few minutes, ensuring I could start stressing about something else in my home in record time.

Best Prices Today: WaterGuru Sense S2