The Shelly Flood Gen4 is a water leak sensor that looks promising on paper. It offers an external probe, battery power, and support for both Wi-Fi and Zigbee. For short-term rental owners, that combination sounds appealing.

Unfortunately, after hands-on testing, this device turned out to be one of the more disappointing leak sensors I’ve evaluated—especially when compared to simpler, less expensive alternatives designed for reliability and low maintenance.

This review focuses specifically on short-term rental and remote property management use, where consistent connectivity and clean installation matter more than feature checklists.

Shelly Flood Gen4 Design & Installation Issues

The first issues show up immediately during installation.

External Probe Cable Problems

While the external probe seems like a good idea in theory, the cable does not lay flat. It ships tightly coiled and resists staying in place, which makes neat placement under sinks or appliances difficult. Instead of sitting cleanly where leaks occur, the cable tends to curl back and get in the way.

For short-term rentals, where devices should be discreet and tamper-resistant, this is a downside.

Large, Wall-Mounted Form Factor

The Shelly Flood Gen4 is larger than most leak sensors and is designed to be wall-mounted. I generally prefer compact, floor-level leak sensors that can be placed directly where water will collect.

Wall mounting:

• Makes installation more involved
• Adds visual clutter
• May prevent guests from moving it, but not moving the cord

It feels like you would need to mount the sensor and then also mount the cable everywhere you want it to run. While that may add to the reliability, these two aspects of the design aren’t great for our use cases.

Poor Battery Access

Once the cover is installed, removing it to change batteries is extremely difficult. Even when wall-mounted, the access point is awkward and not intuitive. For a battery-powered device that will require periodic maintenance, this is simply bad design.

Zigbee Connectivity Problems (Major Deal-Breaker)

This is the primary reason I cannot recommend the Shelly Flood Gen 4.

The sensor supports both Wi-Fi and Zigbee, but for this review it was tested exclusively using Zigbee, which is a preferred protocol for short-term rentals (and any smart homes to be honest). We recommend to avoid adding smart devices to a property’s Wi-Fi network.

Despite being:

• In the same room as the hub
• Well within Zigbee range
• Tested alongside multiple other leak sensors

…it was the only leak sensor that repeatedly dropped offline.

SmartThings would regularly show the device as:

• Offline
• Then back online
• Then offline again

This behavior persisted despite troubleshooting and was not observed with any other leak sensors tested in the same environment.

For a water leak sensor, connectivity reliability is non-negotiable. If a device is frequently offline, you don’t know what is happening with that device—and that defeats the entire purpose of installing it.

Yes, the Shelly Flood Gen4 detects water correctly (and connects to report if it’s offline). But that’s not enough for remote property management.

Short-Term Rental Suitability

From a short-term rental perspective, the Shelly Flood Gen4 misses several key requirements:

• Bulky and visually intrusive
• Awkward battery replacement
• External probe cable that doesn’t behave well
• Unreliable Zigbee connectivity

There are many less expensive leak sensors available that offer:

• Smaller, puck-style designs
• Easier battery access
• More consistent Zigbee performance
• Faster, cleaner installs under sinks and appliances

When managing properties remotely, simplicity and reliability always beat complexity.

Who This Sensor Is (and Isn’t) For

This sensor may be acceptable if you:

• Intend to use it strictly over Wi-Fi
• Don’t mind wall mounting
• Are okay with more involved maintenance

This sensor is not a good fit if you:

• Manage short-term or vacation rentals
• Rely on Zigbee for reliability
• Want low-maintenance, discreet leak sensors
• Need consistent online/offline reporting

Final Verdict: Not Recommended for Short-Term Rentals

I went into this review genuinely excited about the Shelly Flood Gen4, but real-world testing changed that opinion quickly.

Between the awkward physical design and—most importantly—the unreliable Zigbee connectivity, this device does not meet the standards I expect for protecting a rental property from water damage.

With multiple simpler, cheaper, and more reliable leak sensors available, the Shelly Flood Gen 4 is not recommended for short-term rental use.