WHAT IS THE smallest LEAK FLO by MOEN CAN DETECT?

by Margaret · Published November 2, 2021 · Updated November 4, 2021

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Flo by Moen smart water monitor and shutoff system

The goal of this video is to discover the smallest leak Flo by Moen can detect. A previous post covered medium to large loss leak scenarios (How FAST Does Flo by Moen Detect a Leak?), but at some threshold Flo doesn’t cut the water off. Instead, the daily health check discovers the smaller leaks.

For instance, when I first installed Flo, I was running a test under my patio in an attempt to prove concrete is porous.

Flo by Moen detects small leaks and sends notifications

Both the slow flow attempt and the higher flow attempt weren’t strong enough to get cut off during the day, but they were discovered in the automatic nightly health check.

These were very steady streams of water you expect to discover with a $500 unit. Well, a drop every 52 seconds out of my home’s plumbing is not enough to be caught by the pressure sensor to trigger a leak notification. A drop every 6.5 seconds is enough.

Volume of water from drip every 6.5 seconds.

While the health test didn’t catch a drop at the minute mark, Flo actually can help you discover a leak way smaller than a drop a minute. I’ll cover that towards the end of this post and stay focused on the automatic and manual health checks at the moment here.

Unfortunately, that is where the leak testing for this video has to stop and here’s why, along with what you can expect from automatic and manual plumbing checks. This was my fourth Flo unit and I didn’t get a chance to continue finding the limit for my home due to the August heat in Arizona.

Original Flo by Moen next to unit #2.

I also wanted the nightly check to catch it and not run manual checks back to back, to give this video a more realistic scenario. There is also a difference between a manual health check and an auto health test. The manual check warns you it can last up to 4 minutes before you kick it off.

In actuality the Flo by Moen health test only runs up to 4 min.

What you are looking at was my attempt at running a manual health check after the nightly health check did not discover the drop every 52 seconds.

Flo by Moen health test complete.

Since the test only lasted 40 seconds in August of 2020 (as of Sept 2021 it would only last 30 seconds) and a manual health test can run up to 4 minutes if it suspects a very small leak is present, just under a drop a minute is too small of a leak to detect in my home’s plumbing.

Based on the advertised runtime difference, it appears an automatic check may catch a smaller leak than a manual test, but in reality the maximum Flo runs a test is 4 minutes (I’ll be sharing the test results I gathered last month in an upcoming video in a few weeks on the YouTube channel).

I am enrolled in the Flo Protect plan and had the fifth unit sent to a location where it can be installed indoors to continue testing the longevity of Flo in a more protected environment.

Aaaaand I still have the Flo by Moen FloProtect exended warranty and deductible coverage on unit #5 here.

While I could continue the test in the new location, I can’t test Phyn Plus in that new location because it is now installed on my home for similar testing to share with you. None of these water monitors are the same size for an easy swap.

The problem is, this test is very dependent on the amount of plumbing in your home.

Flo by Moen leak test results different based on plumbing volume.

If you have less pipe, Flo by Moen will detect a smaller leak and if you have more plumbing than my trunk and branch system, it may not catch a drop every 6 and a half seconds. If you have a manifold, you can turn off all the valves and individually test each line, which Flo would perform beautifully.

While there is a big difference between 6.5 seconds and 52 seconds, this still gives you an idea of what Flo by Moen is capable of on a real home of about 2000 square feet and how health checks work.

<from more recent tests on another house> Honestly though, I don’t think it could get much bigger than 6.5 because if a health test is only 30 seconds long–no longer 40 seconds–when a leak is not detected, asking a device to detect more than three drops over that amount of time seems unreasonable. Somewhere between 6.5 to 10 seconds seems likely.

Now its on to how to discover a leak of less than a drop a minute with Flo by Moen: overnight testing.

If you saw my video on how small of a leak you can detect with a water pressure gauge, this is EXACTLY the same. We’re capitalizing on Flo’s pressure sensor. First, if you have a tank style water heater you’ll have to completely cool the water inside so that thermal contraction does not impact the results of the test. I covered thermal expansion specifically with regard to it’s interference with detecting a minute leak in this past video. Once you’ve eliminated thermal expansion, turn off the water shutoff to the house and make sure NOTHING uses water for the duration of the test. Then, write down the pressure reading at the start of the test.

Flo by Moen screen capture to compare pressure drop.

While I can’t show you the results with Flo, in the water pressure gauge test, where my goal was to get a drop in pressure of 5 PSI, a drop of water about every 4 minutes will drop the pressure in my home’s plumbing by 5 PSI over the course of 8 hours. At the end of 8 hours, or whatever duration you run the test, compare the beginning pressure reading with the ending pressure reading. If there is a significant enough drop, you have your answer. Again, keep in mind your own results will be different just because there is a difference in the volume of water between your plumbing and mine.

Sample before and after Flo by Moen App screenshots after an 8 hour leak test pressure drop.

This small of a leak will never be caught in a health test and it is unrealistic to expect it to. But it is possible and that’s part of the fun of thinking what you can do with these kinds of systems.