Flo by Moen vs Phyn Plus: Which Detects Leaks BEST?!?
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In the last few months, I shared the results of testing both Phyn Plus and Flo by Moen. I tested both devices across many sized leaks in an attempt to see how fast they turn off water to the house due to potentially large, catastrophic leaks, and I wanted to know what is the smallest leak each unit could detect on my home. I have also shared how the automatic and manual checks work in both systems. In this post we are comparing the results to determine which device detects leaks best.
How do Phyn Plus and Flo by Moen detect water usage and determine if a problem exists? Both units accomplish this feat through a combination of software algorithmic monitoring and learning paired with specialized detection hardware. First, I will share the devices’ software results in multiple leak scenarios. Later, we are going over each system’s nuances: the software and hardware differences, and why the results are not as clear cut as you might think.
Here are some things you need to know upfront.
Phyn Plus as a learning period after you initially install the unit. During this time, the algorithm is learning your household usage patterns and Phyn recommends you do not enable auto shutoff so that your normal life is not interrupted.
Flo by Moen has a hard and fast timeline with a one week learning cycle where the auto shutoff is not an option. Phyn’s learning period is more adaptive, waiting for at least 1,000 water events, which in my house took closer to a month both times–your timeline will vary depending on how often you use water.
Phyn Plus learning cycle differences–remember, auto shutoff can still be enabled when you first install it. That is definitely something to consider enabling if this is a vacation home with limited or no use.
Large leak results:
I ran these tests after the learning cycle was complete. Here, we are looking at the results of how long it took for both Phyn and Flo to shut off the water for medium to large leaks after the learning cycles were complete.
The data shows Phyn’s more conservative approach, not only in the learning cycle, but as you can see, the initial results from the few tests I did run a month after installing the unit are on par with the results from Flo, when Flo was only installed two weeks.
While you can see four months later Phyn allows the water to run for a considerably longer period of time, the algorithm is taking our water usage into account, where we flood irrigate our citrus trees in the backyard.
Phyn Plus 1 month vs 4 month leak results
Phyn Plus same test 4 months apart has much different results based on our normal usage pattern.
I was not able to replicate the test on the most recent Flo because of the reason I covered in this recent video.
Just looking strictly at these limited results, it *appears* both Phyn Plus and Flo by Moen have similar enough results for catching a medium to large leak so it is not easy enough to declare a clear winner. I will go into why this isn’t quite the case after the small leak results.
Flo vs Phyn all leak results
Small leak results:
So now it’s on to the small leaks which are only caught by automatic daily, or manual tests.
Due to problems with device longevity in the desert, I was only able to prove that Flo detected a leak somewhere between 6.5 seconds, which was caught, and 52 seconds, which wasn’t caught. Meanwhile, I was able to pinpoint Phyn Plus catches leaks down to just over 4 seconds.
Phyn Plus smallest leak automatically caught
Even with limited Flo testing, Flo is clearly the winner at finding the smallest leak automatically.
But it’s not that clear…THIS IS THE IMPORTANT PART!!!
Here is the rest of the story on specific scenarios I’ve encountered and how these devices work. I’m getting into mad details here so if you get the point right away please use the jump to the next one to make sure you understand each observation *especially* if you are trying to decide on the best system for your house.
#1 Differences in how these devices share the information with small leak detection.
Phyn shares the results of automatic and manual plumbing checks in the plumbing check log, which clearly shows the PSI drop over the course of the test.
Phyn vs Flo app differences in shared information–this picture will get replaced because it is somewhat misleading. Flo gives sort of similar information in the event of a suspected leak. However, the Flo nightly check details state “Congrats! your home water system passed the Health Test on January 3 at 2:01 am. You’re Secure.”
Knowing my home’s baseline PSI drop over 3 minutes means I can look at the plumbing check log and take note if anything is more than .14 PSI.
Sample regular week PSI drop
The drawback is this is a manual process because it requires you to look at the data, know your baseline psi behavior when no leak is present, and subtract the numbers yourself from time to time. The data isn’t exportable. BUT it IS possible to find an extremely small leak. In my case, if I look for a drop of .3 PSI I’m looking at a drop of water every 25 seconds.
For instance, I actually had a gasket fail on our toilet diaper sprayer. I was pretty upset about this when I first found it–I thought one of our kids was jacking around in the bathroom only to find there was a legitimate leak.
Real sample leak
For those of you who saw my video on how to change a toilet supply line where the old one failed, well, this seems to be the unlucky toilet in the house. In any case, Phyn didn’t send me an alert on this issue, and you can see by the time I figured out how to shut it off, it was up to a drop every 8 seconds. However, it is possible to detect a leak, just by knowing your baseline numbers and looking at the app on occasion. Unfortunately, there is no way to export this data at this time so you can’t make your own automated excel type tracking like you see here, but you CAN see the leak was clearly on it’s way to being detected.
New leak PSI drop over time using Phyn Plus PSI drop.
I have now made a weekly reminder to go into the Phyn app and look at the plumbing check history.
With that suggestion, don’t check on Friday or a holiday–I recommend checking on Monday or Tuesday so you don’t incur any extra plumber fees for off hour calls.
If you do not know why there is a drop in PSI and you are curious–you are not alone–I was there too when I first installed Phyn Plus. I’ve included a few videos here which explain this phenomenon.
WHY DETECTING A [small] PLUMBING LEAK IS HARD because of your water heater: THERMAL EXPANSION
THERMAL EXPANSION IN A CLOSED VS OPEN PLUMBING SYSTEM: Causes, Risks & How to Deal With It
The notifications history in Flo does not log the PSI drop so you don’t have this same insight into your plumbing system.
#2 The length of a plumbing check is also notably different.
If there is no leak, the leak is too small or the leak is sizable, but less than .2 gpm Flo’s health check only runs 30 seconds long. This is true of both the manual and automatic tests. If it does catch an extremely small leak close to the minimum the device can detect, the health test can run up to 4 minutes.
Flo by Moen tests with different sensitivity slider settings in the Flo app.
Flo by Moen differences in health checks between different homes
In comparison, the automatic plumbing check in Phyn Plus runs a minimum of 3 minutes, with a smaller leak causing it to run 10 minutes.
You can check out the specific details in these past videos to compare how each system performs manual and automatic plumbing checks or health checks.
Phyn Plus’s plumbing tests run 2.5 to 6 times as long as Flo by Moen, depending on the size of the leak, and Phyn gives you the data for your own use.
While Flo automatically alerts you on smaller leaks, Phyn’s tests run longer and they share the data.
#3 How the devices hardware and algorithm detects different leak sources.
Now I’m going to move back to the medium to large leak scenario results, starting off with this excerpt from a past post on Phyn Plus:
“It is important to note at this point, and this is the really cool finding in this post so stick with this [still cool in this post] Phyn Plus has an ultrasonic pressure sensor, which is a different design from water monitors that use an impeller or turbine to mechanically measure the flow of water. What that really translates into is each fixture in my house, and yours, has a different pressure signature so Phyn Plus can tell that I’m using the outdoor hose bibb. Since I generally use it for longer events, Phyn is more likely to let me run that fixture longer than let’s say, a shower that is only used in the summer due to the plumbing run of at least 50 feet from the water heater. Since it is now summer, we’ve started using the shower again and Phyn started sending alerts the first two times we used it at the 14 minute mark both times. The Phyn Plus has since learned about the “new” fixture and has not sent another notification.”
The real alerts from this scenario. Phyn Plus identifies new fixtures! (Also, remember you can click on a photo to get a larger version that is legible.)
So if you were alarmed at that 274 gallon number, the fact that Phyn saw an unusual usage and detected it at only 19 gallons used while also allowing me to use the hose bibb during my irregular watering in an attempt to fool Phyn’s algorithm, that should give you some peace of mind.
This scenario shows a big difference in the detection algorithm and design between these units: Flo uses a turbine to detect the flow of water while Phyn uses an ultrasonic flow sensor which works in conjunction with the pressure sensor.
Flo by Moen on the left vs Phyn Plus on the right: water monitor design differences.
The fact that Phyn caught a new fixture at 19 gallons while allowing another known fixture to run hundreds of gallons for a usual event means there is definitely some extra processing going on inside Phyn. Flo has a pressure sensor as well, but I can tell you that Flo did not alert us for the second summer that we had it installed and used the shower only in the summer.
#4 Hardware differences
This next point can impact both small and large leak detection.
Some initial feedback from long term users of Flo have observed corrosion buildup on the magnets in the turbine or have experienced flow sensor issues, which is how Flo measures the rate of water flowing through the unit. As corrosion builds up this can cause inaccuracies in the measured flow rate.
This is not an issue for Phyn since they use an ultrasonic flow sensor which has no moving parts.
You can check out this post for a possible repair for Flo’s turbine, if you encounter this.
post
Last mathematical thoughts…
Here are some of my last thoughts concerning what these devices are giving you and the very real limits on leak protection. Also to give you some context of what you should expect.
Let’s step back and look at the small leak results from a higher level. Admittedly, I didn’t find the bottom threshold for Flo, but let’s go a little further and say Flo catches a drip every 10 seconds, assuming it will detect 3 drops of water over the course of the initial 30 second automatic health check, triggering the algorithm to run the full 4 minutes. Even at this generous number, the water loss is ¼ a cup an hour versus just over half a cup an hour in Phyn’s result. That’s 6 cups a day for Flo and 15 cups a day for Phyn.
6 cups of water staged to “leak” to see how far it extends in my kitchen.
HOWEVER, no matter what, 6 cups a day is significant when it is inside a wall…or anywhere!
The 6 cups of water on the floor.
Is the difference between 6 cups and 15 cups enough to help you decide between the two systems?
90 drops = 1 TBSP
Drop of water every 4 seconds
= 15 drops/ min = 900 drops/hr = 10 TBSP/hr = 0.625 cup/hr = 15 cups / day
Drop of water every 10 seconds
= 6 drops/ min = 360 drops/hr = 4 TBSP/hr = 0.25 cup/hr = 6 cups / day
Drop of water every 6.5 seconds
= 9.23 drops/ min = 553.85 drops/hr = 6.15 TBSP/hr = 0.384375 cup/hr = 9.225 cups / day
Please note, I have some SIGNIFICANT plumbing runs in my house. Hopefully you have less and your device will catch smaller drips. Otherwise, these numbers only go up.
Not my house and I love this manifold system, but the volume of water in this system is a downside for a whole house small leak test. Now if you test each run individually we could really have some fun finding a ridiculously small leak and maybe that’s not a bad idea to run a series of tests like that on a regular maintenance schedule–especially on toilet lines…
Taking a second step back, am I saying, these companies are doing a bad job?!?
Absolutely not.
You have to remember they are creating a device and algorithm for a plumbing system that can work in a one bathroom house and a castle.
Sample one bathroom house. Aren’t those some pretty floors?!? 😉
In addition to huge differences in volume of water between even two houses, water in plumbing is always changing with thermal expansion, and customers quite simply do not want to have a lot of false positives.
A quick preview into how pressure changes based on a leak and thermal expansion.
In other words, there better be a leak when a notification comes across. Phyn and Flo are doing excellent work at detecting leaks and providing a solution to keep you from having a catastrophic water loss.
Also note, these devices are not going to save you from all water damage…
All water damage is not preventable.
…but when I’m not home a few hundred gallons is a lot less than a thousands of gallons that cannot be shut off automatically or remotely.
If you don’t have some massive water usage like we do from time to time, your cutoff threshold will be a lot lower as well.
Also, consider I allowed all these tests to run to completion, but both devices give you alerts, which you can respond to well before the valve shuts off–this is important if you need to keep the water running, or if there is an actual leak, you can shut off the water to your home sooner.
You can check out my past videos on what happens in a real scenario for both systems.
Both companies are improving their algorithm as time goes on, so really take this all into account as these videos and posts age out. For example, two weeks into my first Flo in May of 2019 the algorithm allowed the water to run 464 gallons for 68 minutes.
The Flo by Moen email critical leak notification.
That’s definitely not the case anymore–I appreciate the shorter cutoff, thank you Flo!
Looking back at the hard numbers, am I saying this is how Flo by Moen and Phyn Plus will perform in your home?
Yes and no.
Of course, my goal for this post was to compare the results to show which water monitor detects leaks best, but as we just went over, it’s not as simple as just looking at the hard numbers.
Test numbers are nice, but having lived with both, there are some major differences that cannot and should not be overlooked.
What I really want you to understand is how these devices’ detection monitoring software and hardware work together and protect your home long term. I have also shown what information each company’s apps share with you and what you can do with that information.
However, your monitoring results will be different than mine based on your household’s behavior patterns and the amount of plumbing in your house.
I pushed small leak testing further in separate posts on Phyn Plus and Flo by Moen.
WHAT IS THE smallest LEAK PHYN PLUS CAN DETECT?
WHAT IS THE smallest LEAK FLO by MOEN CAN DETECT?
Both can detect leaks as small as a drop every 4 minutes on my home, and you can check those posts out.
This is just one example of how you certainly have a lot more insight and protection on your plumbing once one of these systems is installed.
Last, this post is not meant as the determining factor when deciding between which unit you want to install on your home. There are a LOT. OF. DIFFERENCES. which need to factor into your decision. All of these concepts can and should be applied to any system you are currently considering.
All of these testing posts and videos I mentioned are the leadup to the actual comparison post and video between these two systems. And since this is the backstory of the YouTube channel if you’ve been following on there, now you can see the master plan of why each of those seemingly odd onesie-type videos came out. I’m on this ride too not knowing exactly when the comparison video will come out because as each seemingly simple video comes out it often expands into a new tangent. These devices are really interesting and how each company has addressed each issue is surprisingly very different and has different consequences.
In the meantime, you can check out my cost comparison post right now.
The REAL COST of Flo by Moen vs Phyn Plus
PRICING / REVIEWS
○ Phyn Plus (10% off) – https://www.phyn.com/plus-smart-water-assistant/ enter discount code ‘Margaret10’ at checkout
○ Other pricing/reviews on Phyn Plus on Amazon
○ Flo by Moen
RELATED POSTS:
The ULTIMATE Phyn Plus Resource [OUTSIDE of Phyn.com, of course]
