smart RO – A reverse-engineering experiment on a Waterdrop G3P600 reverse-osmosis system shows how its smart faucet communicates with the RO unit. By probing a four-pin serial connection and designing a custom PCB, the researcher connected the system to Home Assistant—un
The moment a reverse-osmosis system starts talking back is the moment things get interesting—and for one tinkerer, it ended with a custom PCB and Home Assistant running the show.
Reverse-osmosis (RO) systems are a route to cleaner drinking water. The Waterdrop G3P600 model that [Tomasz Wasilczyk] recently purchased leans into the trend of “smart” appliances: its faucet includes a 7-segment display and a cluster of LEDs. and those lights connect to the actual RO unit through a four-pin connector.
That cable wasn’t just decoration. It created an obvious question for anyone willing to get their hands dirty: what protocol runs through that link?
The work quickly moved beyond theory. With more custom PCB work. the practical goal became clear—make the system smarter in a way that integrates with real home setups. The faucet and RO unit could potentially be plugged into a home automation system with ESPHome support. and the system could also be made to play nicely with refrigerator lines.
What that integration can do depends on what data actually travels between the RO unit and the faucet. In this case, the available signals were extensive. The researcher found that the RO unit could send information related to filter health. water quality. pump status. air temperature. and faucet state.
The four-pin connector itself turned out to be the key. It behaved like a basic serial link carrying 5 V, ground, and a 9,600 baud connection. Once the hardware behaved like something familiar, deducing the protocol became straightforward. The faucet’s own display and LEDs also helped guide the mapping—what lit up corresponded to what the system was reporting.
To bridge the gap between the RO unit and automation, a custom PCB followed. But the experiment didn’t stay clean. After one blown-up fuse—caused by applying 24 V instead of 12 V when tapping power from the RO unit—the system finally came back to life.
From there, the results sharpened. The RO system could be connected to Home Assistant. and from that setup. the full functionality and the conditions that triggered different states could be mapped. The faucet wasn’t just displaying status anymore; it became a window into the RO unit’s internal behavior.
There’s still more to discover and reverse-engineer inside the unit. but the researcher has clearly found a practical starting point—one where a smart faucet isn’t a sealed appliance. It’s a controllable, monitorable system that can plug into broader home automation instead of sitting behind its own LEDs.
reverse osmosis smart faucet Waterdrop G3P600 Home Assistant ESPHome reverse engineering serial protocol custom PCB home automation water quality monitoring smart home security
So wait they hacked a faucet… from a 4-pin plug? That’s scary but also kinda smart??
If it can be “hacked” then it’s basically unsafe drinking water, right? Like people’s filters are getting bypassed or something.
Home Assistant??? I have that too and now I’m like, should I unplug my RO stuff? I didn’t know faucets had 7-seg displays connected to the RO unit.
Bro they blew a fuse by putting 24V instead of 12V and that’s somehow “the hack”? I mean I know serial pins exist but most folks aren’t gonna do custom PCBs. Sounds like a hobby project that got stretched into clickbait. Still, who approved these things being connected at all.