The Problem with ORP
The first Sutro Smart Monitor used a technology called ORP (you can see our demo at TechCrunch back in 2015 at CES’s Hardware Battlefield). The two wires sticking out of the chlorine floater are nothing but a pH and ORP sensor. ORP stands for Oxidation-Reduction Potential. It measures the oxidizing properties of any sanitizer present in the water. When chlorine is free to oxidize, sensors generate a millivolt reading, expressed as ORP. If the chlorine isn’t free and available, a millivolt reading will not be generated. At the time, ORP was the go-to method to measure this because it was electronic meaning you did not have to do the manual process of dropping chemicals into a flask of water.
The problem with ORP (which Ravi figured out 3 years ago) is that it drifts all over the place and the sensor needs to be calibrated with a known standard. This is cumbersome and leads to all sorts of inconsistencies in measurements.
As an example, ORP measurements vary by time of day since sunlight (actually the UV part of sunlight) will cause cyanuric acid (CYA) and chlorine to combine, which makes the chlorine less free to do its job. It still can mind you, but any ORP reading will “show” that it can’t. Or that the pump running can send signals through the water which will affect ORP and cause it to go wacky. Kind of like passing through a metal detector if you have a pacemaker or a titanium hip.
The first ORP Smart Monitor had lots of problems that nearly bankrupted Sutro. It was only through Ravi’s hard work, pool boy experience, and mechanical engineering background that he realized the best way to test water would be to create a “mini pool boy” robot (like the Roomba vacuum). He thought why not take the dropping chemicals in a tube of water and create a robot that would do it.
Reason #1: The “easy” way did not cut it and was wildly inaccurate.
A Roomba For Testing Water
Our Friend (and Inspiration), the Roomba
You have probably seen a Roomba or know someone that has one. For those of you who don’t know what a Roomba is, it’s a robotic vacuum cleaner that learns your rooms and vacuums them automatically. It’s probably the best comparison we can draw for the Smart Monitor. Just imagine a Roomba in your pool sans the vacuuming.
The Roomba was first introduced in 2002 by a company called iRobot. iRobot was founded in 1990 by Massachusetts Institute of Technology roboticists with the vision of making practical robots a reality, iRobot has sold more than 30 million robots worldwide. Currently a Roomba sells for ~$299, depending on the model.
Robots Do a Lot of Work
Robots perform functions that humans can do as opposed to passive electronics or just a sensor. All this work, especially the moving of things in physical space, takes a lot more effort and smarts to make it work. If you compare the process of taking a Smart Monitor Measurement vs an ORP Measurement, you’ll see what I mean:
| Smart Monitor | ORP Measurement |
| Prime Flow Cell Siphon Sample Titrate Sample Measure Color Calculate Result Report Result |
Measure Potential Calculate Result Report Result |
The first part of our process relates to taking in an actual sample of the water and adding drops of reagents — just like you would do with your home kit. That’s the robot part and while it’s more complicated (and costly), it’s the most accurate way to do it.
The pumps, flow cell, titration and precision syphoning is where the majority of the cost adder comes from (about 35-50% of the total cost). That’s why we have to charge more. It’s worth it (to us anyway) because if we get accurate measurements of pH, Chlorine, and Alkalinity, we can give you the best treatment recommendations.
Reason #2: The mechanicals allows us to take an actual sample of your water.
We know that it’s important to test your pool (or spa) water regularly to ensure that it’s crystal clear and ready for a swim. An investment in a Sutro Smart Monitor will ensure that you’ll always be ready for a swim. Here is what you get when you invest in the best pool (and spa) water testing robot:
- Monitor + Hub + 2 rechargeable Monitor batteries.
- Automatically measure pH, Chlorine, and Alkalinity 3 times a day
- One Year of cartridges (shipped monthly) + monitoring
- iOS + Android App
- Expert treatment recommendations based on Your Chemicals.
- 60-day no-hassle money-back guarantee
- Phone + Email Customer Support
- Access to exclusive Sutro’s Cabana Club Facebook Group
- Lifetime warranty
Join the top 10% of pool owners who demand precision monitoring to keep their pools and spas safe, stable, and crystal clear.