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BRAND:  yolink        MODEL: YS7903-uc  

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Water Leak Sensor 4
Water Leak Sensor 4
Water Leak Sensor 4
Water Leak Sensor 4


One Water Leak Sensor 1, "puck" style water leak detector.



This product requires a YoLink Hub or SpeakerHub!


Free U.S. Shipping, Orders $50 & Up

Hassle-Free 60 Day Returns

2-Year Warranty

Do-It-Yourself Installation

U.S. Phone Support Available

100% Satisfaction Goal






Home Assistant

Raedius Web Console





  • Smart wireless water leak detector, with water-sensing electrodes on the top and bottom, sealed and waterproof
  • For "rope" or cord style water leak sensors, see the Related Products section below.


  • Built-in water-sensing probes, on top and bottom, self-contained inside the rugged IP68-rated waterproof housing
  • Portable; may be placed anywhere in your home or wall-mounted
  • Wireless operation; no 120V outlet or wiring required
  • Battery-powered (two standard alkaline AAA batteries, included)
  • LoRa long-range/low-power technology offers 5+ years battery life, compared to 1+ year for other brands
  • Real-time water sensor status displayed on the YoLink app
  • Alexa voice assistant and IFTTT integration
  • YoLink Control D2D device-to-device pairing allows for the Water Leak Sensor to directly control other YoLink devices, without an internet connection, and without power ("No WiFi, No Internet, No Power - No Problem!")
  • YoLink’s industry-leading long range communication (1/4 mile, open air!) allows for operation in larger homes and in areas difficult for other wireless systems, such as basements, separate garages/structures, and even outside your home
  • Two year warranty


  • Exceptional value; high-quality wireless smart leak/flooding detection at a great price
  • Be informed immediately of off-normal environmental conditions, such as water from leaks or flooding, in your home and property, before expensive repairs are required
  • Create custom automation using the YoLink app, to trigger responses from other YoLink devices, such as the Siren Alarm
  • Compact design allows for placing the sensor where others may not fit
  • Easy to install and portable; move to other locations as needed
  • Lower cost of ownership than other technologies; low-power operation means batteries may last over 5 years, compared to 1 or less from other brands
  • Carefree maintenance, with more years between battery replacement
  • Low-battery alerts give you advanced warning that it is almost time to replace the batteries
  • Uses standard alkaline batteries (2 AAA batteries); no Lithium or special batteries required
  • Works with the convenient and user-friendly YoLink app
  • Extremely easy and fast installation using the YoLink app with Scan & Play

  • Place the YoLink Water Leak Sensor anywhere that is at risk of high moisture or water, due to leaks or flooding
  • Use the YoLink smartphone app to remotely monitor the status of your water leak sensors in your home, rental property, condo, summer home, or business (internet connection and YoLink Hub required)
  • YoLink’s industry-leading long range communication allows for placing the sensor in your out-buildings, separate garage building, barns, greenhouse, etc.
  • Some common applications include:
  •    Locations at or below grade, subject to water incursion
  •    Basement floors
  •    Near sump pumps
  •    Under water heaters
  •    Under sinks
  •    Next to toilets
  •    Under or near laundry machines
  •    Under dishwashers
  •    Under refrigerators & ice machines
  •    Under fish tanks/aquariums
  •    Under swimming pool pumps and equipment*
  •    In attic spaces under a leaky roof*
  •    Inside hot tubs*
  •   *Refer to device environmental limitations in Technical Specs, below. Use this device outside the recommended ranges at your own risk; warranty may be voided, etc.
  • Semtech® LoRa® RF Module YL09 microcontroller with 32-Bit RISC processor
  • Color: White
  • Dimensions (L x W x D): 2.44 x 2.44 x .96 inches (62 x 62 x 24.5 mm)
  • Multi-color status LED (underside)
  • Set button (underside)
  • Power: 2 AAA batteries (3V DC)
  • Environmental:
  • Operating Temperature Range:  -4°F – 122°F (-20°C – 50°C)
  • Operating Humidity Range: ≤100%RH non-condensing
  • Intended for indoor use only
  • (1) YoLink Water Leak Sensor 1 (batteries included)
  • (1) Quick Start Guide
  • YoLink Hub with an internet connection (wired Ethernet or 2.4GHz Wi-Fi). Refer to the Hub user guide for additional information
  • Smartphone or tablet running iOS 9 or higher, Android 4.4 or higher
  • Tools Required: None
  • Installation Difficulty Level: Super Easy
For full functionality, including for the app to work, YoLink devices must connect to at least one hub (YoLink Hub or SpeakerHub), and that hub must have an internet connection. Unless you are adding devices to an existing YoLink account, or unless your building is covered by an existing YoLink or Raedius wireless network, please add one hub to your order.

Automatic water shut-off is an important part of a comprehensive water leak protection system. Consider adding a Bulldog Valve Robot or a Motorized Valve and Smart Wireless Valve Controller to your YoLink system. Learn more here

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Siren Alarm, Indoor Siren, HUB REQUIRED
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Water Leak Sensor 2
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YoLink Water Leak Sensor 3
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YoLink LoRa 1/4 Mile Long Range Water Level Monitoring Sensor, Alexa and IFTTT. YoLink Hub Required - YoLink
Q:  Are the batteries replaceable?  A: Yes. On the underside of the sensor, after removing the waterproof screw hole plugs, remove the four screws to access the battery area. The sensor uses two AAA batteries, standard alkaline (lithium is optional), but do not use rechargeable batteries. You should get upwards of 5 years between battery changes!  

Q: Does this detector make a sound?  A: No. As part of the waterproof requirements, this device can not have an audible sounder. We offer the Water Leak Sensor 2 and 3, with built-in sounders, as well as several siren options and a talking- and tone/sound-playing audio hub, the SpeakerHub. 

This product is a member of the following collections:

Water Sensors Collection

Water Leak Protection System Collection

Smart Water Solutions Collection

Do you have questions? We have answers!

Do you have questions? We have answers!

Please fill out the form below, or if your matter is urgent, please call us at  949-825-5958. Please note our Irvine, California office hours: 9AM - 5PM Pacific, Monday through Friday. You may experience waits as we attend to previous customer requests. 

Please fill out the form below, or if your matter is urgent, please call us at  831-292-4831. Please note our Irvine, California office hours: 9AM - 5PM Pacific, Monday through Friday. You may experience waits as we attend to previous customer requests.