Water flow meters


Thanks Jonathan for setting up the forum.

Timing is great as I’m currently browsing the internet looking a flow meters for the house so figured I’d ask here!

Does anyone use flow meters and can recommend a model? I will measure pulses using Arduino most likely pushing MQTT messages to openhab. Will likely grab something like this to do some testing.


Hi Kerry,

I have looked into using various methods for measuring I have in fact bought one that looks very similar to the one you are looking at. I have never put it in line, simply because they are made of plastic and I have some doubt of the longevity of it, and if it fails when you are not there, the water can make quite a mess.

There are ultrasonic flow meters available, but they are expensive as far as I have seen.

The last way may be to use an optical sensor that measures the light that is reflected by the digits on the display (depends on your water meter). I plan on using this method on my gas meter which has a small silver stripe on the least significant digit which makes it very easy.



Hi Kerry,

It’s good to see this being useful!

I did a project about this in Practical Arduino. The example code is still up on GitHub, but unfortunately I let the actual domain for the book expire and a squatter grabbed it so the only other place it’s documented is in the book itself:

Jon :slight_smile:


I’d like to see something for our reverse osmosis system since we overflow when filling up water glasses about once a week. I looked at the flow meter you linked but really need one for little 1/4” tubing for the RO plumbing. I would incorporate it into my kitchen controller mounted under a cabinet to flash my embedded LED strips blue while running.

BTW - kitchen control running EtherTen powered by Freetronics mid span injector. :slight_smile:


Wow, this is awesome! So you embedded LED strips behind the tiles? I thought I was cool putting 4 LEDs behind a single tile, but you’ve taken it to another level!


I bought the flow meters for my hot water loop from amazon

I haven’t used them yet but I plan on doing the project next week. I use the flow sensor to detect hot water demand and turn on the loop pump. I have a temp sensor at the hot water outlet of the tank and a temp sensor at the faucet. My arduino sketch will be set to turn on the pump relay when it senses flow if the faucet temp is .75xT(tank)


so basically
F1=flow meter 1
Tf= temp faucet
Th= temp hot water heater out
R1= relay 1
F1=on (flow meter 1)
Tf< .75 Th
R1=on (turn on pump)
R1=off (turn off pump)

I don’t actually use the flow meter to track gal/min but to indicate an on/off state although I might use the flowmeter in the future to track water usage (my room mate takes ridiculously long showers, daily). I could use a pressure sensor instead of a flow meter but since I am using an arduino for the temp sensor, this hall effect sensor seems like the perfect item. Also I like that it’s made out of brass, rather than plastic, at about the same price.


Looks nice, I’ll probably grab one of these over the next couple of weeks to do some testing


Pressure drop is an interesting idea. That might work for my application since I can’t find a flow meter for the small lines in the RO system.