Inline pipe water temperature sensor?

What I’d like to do is monitor the water temperature in pipes at a couple of locations under my house. The crawl space can get pretty cold. What we do now is run the water at a trickle if it’s going to be below freezing.

I’m wanting to make an automation that activates a recirculating pump if pipe water temp gets too close to freezing. The return line would just be the normal cold line. Thus the water heater would be warm the water all the pipes if it got too cold. Basically I’d use the water heater to ensure my pipes don’t freeze. This seems a lot safer than heat tape, which I find sketchy at best. Further it could be used to heat up water at various faucets so we don’t have to run it until it’s hot enough. This could save a lot of water, while not using nearly as much energy as a traditional re-circulation system as it wouldn’t be running unless someone was wanting hot water.

Basically for implementation I’m imagining Home Assistant a smart relay like a Shelly unit turning on a recirc pump until the water temp reaches a predetermined temp ranged then turning it off. Sensors under the house, and at faucets would provide data for both automation types.

So if someone hits a programmed button, in say the kitchen, a pump would recirculate the water until it was hot. Likewise if a pipe under the house got too close to freezing, a pump would recirculate the water until both lines were back in a safe temperature range.

Unfortunately not finding a lot about temperature sensors for water in pipes, which brings me here.

What I’m considering doing is using a temperature sensor on the metal pipe connectors. We have pex, but the connectors are copper. The sensor wouldn’t have to be exact, I bet I could get a close enough reading by checking the temperature of the metal.

I’m just wondering does anyone know of any good pipe temp sensors for this? Is just checking the connector temp likely a good idea?

ETA: we live out in the country, so cloud things are slow, and flakey. Needing something that connects to HA locally without the cloud


A DS18B20 attached to your copper fittings should work nicely.

You can use ESPHome or Tasmota to connect locally to Home Assistant.

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Get something like this. You can install it in the pipe and then use any PT100 or DS18B20 sensor with ESP, Arduino, Raspberry or some Z-wave controller.

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I’m using DS18B20 on a ESP8266 using ESPHOME. It’s not perfect but gives me a rough idea when there is flow.
I just have mine taped to the pipes. BUT you could also the sensors with pipe insulation to sense more of the pipe temps.

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Everyone’s suggestion of DS18B20 seems to be the key! Did a lot of reading, it’s quite a rabbit hole. ESPHome, Tasmota, ect. Found out there’s a Shelly addon that uses DS18B20 probes. Only downside is it only will connect 3, so it’s kind of limited, but it’ll work in my use case at my current skill level.

Looking into BebeMischa’s suggestion of immersion tube now, but I think digiital’s suggestion of wrapping the sensors in insulation would probably work. the pipes are already insulated, and close is good enough.

Thanks for the suggestions!

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using ESPHOME is really easy to get this up and running and probes are inexpensive as well … not complex wiring.

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Well in my use case the Shelly also doubles as a power source for the sensors and relay to control the pumps which simplifies the installation a bit. Plus it can be automated directly on the unit, so a cat accidentally unplugs the Home Assistant Pi, which has happened. Then there’s backup automation to keep the pipes warm.

Getting off topic, but I’m thinking once I get winterized, about making an esphome soil moisture sensor for some potted plants, and an esphome air quality, humidity and temperature sensor for the bedroom. I was also reading about using it as IR blaster, which would be nice to control some things like the heat pump. Replacing the crappy Mr. Cool automation options with Home Assistant would be a nice boon.

So my interest is def peaked in esphome.

Just a follow up. Ended up building the ESPhome sensors after more planning made realize the Shellys would be too far away from the pipes. They work great! Very simple to set up. Only real issue is I’m not super good at soldering, but that’s more a personal practical problem.

Thanks everyone for recommending them!

Hey :slight_smile: I need temperature sensors for a similar use case.
How do I get the sensor data using the shelly (hardware) add-on in HomeAssistant?

What case are you using for the esp8266?

None, I just left it in the corner… One of those winter projects.