Sutro vs pHin- What Other Reviewers Won’t Tell You!

Every dedicated pool owner knows that balancing and maintaining the pool chemistry is no walk in the park. Not only do you have to keep track of something that is not visible to the naked eye, but also strive to make sure it stays within a narrow range.

While pool water testing strips are an accurate and cheap way to measure pool chemicals, not everyone has the time and energy for that. This is where the smart pool monitoring devices come in.

Sutro and pHin are two of the top tier smart pool water sensing monitors that have been launched in the past decade. This article compares and contrasts the salient features of Sutro and pHin.

We also made a comparison of Sutro to WaterGuru, another worthy competitor, for the best pool monitor available.

Products and Ease of Use


The Sutro monitoring system comes with the monitor itself, two rechargeable batteries, a cartridge that holds the test reagents, and an adapter. The monitor is designed in a minimal and sophisticated manner, but is quite large as compared to pHin. 

The setting up and installation of Sutro is quite uncomplicated. It is made further easier by the detailed users manual that comes with the unit.

All you have to do is install the app, connect the unit to your home wifi via a hub, and then drop the monitor in your pool.

The canister itself is 15 inches long, which is quite a size. The fact that it floats around in the pool between the swimmers might be a nuisance for some but atleast it looks good.


The overall structure of the pHin unit is much more compact than Sutro. The monitor is a smart, white device that floats in the pool.

Accompanying the monitor is a wifi bridge, a tether rope and a calibration kit containing the test strips. 

The process of setting up the pHin monitor is pretty straightforward too, and is in fact, similar to that of Sutro. An additional step, however, is the setting up of the Wi-Fi bridge.

A unique feature of pHin is that its chemicals come in the form of color-coded pods. They are easier to use as you do not have to go through the process of identifying or measuring them.

Performance and Efficiency 


Sutro is remarkable in terms of its excellent performance and wide coverage of pool parameters. It can accurately measure the chlorine, bromine, pH, free alkalinity and water temperature of the pool.

Sutro is superior to pHin in terms of accuracy, which is mainly due to the fact that it uses liquid LaMotte reagents instead of the ORP method. The use of these reagents reduces the margin for error to a very significant degree.

With regards to efficiency, Sutro is an absolute trooper. It records and presents the free chlorine levels and pH every three hours, the water temperature every hour, and the free alkalinity once daily.


Although the readings of pHin have been successfully compared to those given by test kits, it does not fare exceptionally well. pHin employs the ORP method for the measurement of pH, chlorine and free alkalinity.

The ORP method does not calculate the actual ppm of the parameters, but instead is an estimation of them by measuring other related values. This creates a room for discrepancies and errors.

The water temperature, nonetheless, is measured very accurately.

The process of obtaining readings from pHin is rather inefficient. You have to dip a test strip in the water, match the reading to the calibration card, take a picture of it and then send it over to an agent for matching and analysis. This process is not only lengthy but also cumbersome.

Durability and Maintenance 


The Sutro monitor itself is made of a fairly sturdy material, which makes it very durable. However, the fact that it is large in size and floats around in the pool makes it prone to getting hit by the swimmers.

The monitoring system comes with one cartridge that contains 3 to 10 microlitres each of the test reagents. These perform up to 90 tests, and last for about one and a half months.


The pHin monitoring system has a life expectancy of 2 years, which is one of its major downsides. After 2 years, the battery and sensor of the system fail and need replacement. Thus, it is not very durable.

Furthermore, as pHin is no longer available in the market, this means that you will not be able to find replacements in the future.

The system comes with 25 test strips. This means that you will have to buy new ones after around a month.

Apps and Subscriptions


The Sutro app is elegant and easy to navigate. It has a very minimal layout, and the information is presented in an organized and simple manner.

It, however, requires a hub to connect to your wifi network. The data is categorized, and extra information can be obtained by a dropdown menu.

The app also notifies you about changes in your pool chemistry, and gives recommendations to keep the chemicals in balance. In addition, you can also track the pool chemical levels over the past weeks or months.

Nonetheless, the app requires a monthly subscription fee which makes it fairly costly. The subscription fee also covers support, guidance material and cartridge replacements on demand.

For more information on the monthly plans, we recommend visiting Sutro’s official website and then selecting a plan.

Sutro App


The newer version of pHin app has a modern look, with separate categories for different data. It presents the pool chemical levels in a pretty straightforward and easy to grasp way.

The app tells you when a chemical is out of balance, and which color pod to use to correct it. It also stores data of the past 90 days, and allows you to reach out to the customer service for assistance or to get chemicals.

pHin app does not require a mandatory subscription, but you can opt for an annual subscription option that is supposed to help you get a free replacement for as long as you are subscribed.

However, it is pertinent to mention here that pHin has been discontinued so I can not say much about the future.

pHin App

Cost and Value for Money


Sutro lies at the high end spectrum of pool monitors. It is comparable to pHin in terms of its initial buying cost. The initial price may even be lower if you avail the $50 discount that they offer by using our discount code “THEWATERHOBBY”.

However, as mentioned above, the app of Sutro requires a monthly subscription fee, so the overall cost of running the system may be a bit higher than that of pHin.

Considering the capabilities of the system, it is safe to say that the higher price is more than justified due to Sutro being one of the most premium pool monitors right now. It is also for this reason that Sutro topped our recommendations list for the best automated chemical monitors.

Official Discount

You can also visit Sutro’s official website and avail a discount of $50 by using the discount code “THEWATERHOBBY”

Alternatively, you can go check the price from Amazon as well.


pHin also retails for a comparatively higher price than most other testing systems in the market. You can check the updated price on Amazon here. Although the app does not necessarily require a subscription fee, you have to pay some amount if you wish to utilize some extra features.

Moreover, the test strips need to be purchased almost every month, which adds to the cost. Given that the system lasts for merely two years, the hefty buying cost puts a question mark on the value offered for the money .

Conclusion- Which One to Buy?

Sutro and pHin both have been prominent players in the world of smart pool water monitors. However, when weighed against each other, it is not hard to conclude that Sutro has more pros.

It does the required job well and you do not have to go through the tiresome and costly process of replacing it every 2 years like pHin. This concern is further aggravated by the fact that pHin is no longer being brought to the market. Thus, Sutro is naturally a much better investment.

If you have decided to go with Sutro’s MySutro Pool monitor, we recommend buying it from Sutro’s official website to avoid any hassle and avail a discount of $50 by using the discount code “THEWATERHOBBY”.

We also made a comparison between pHin and WaterGuru, which is another noteworthy competitor to Sutro.

If you decide to go with the conventional test strips, make sure to read our rundown on the most popular ones here: