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YoLink Water Sensor 1 Manual

Water Leak Sensor 1 (YS7903): Installation and User Guide

User Guide Conventions

The following icons are used in this guide to convey specific types of information:
⚠️ Very important information (can save you time!)
🤔 Good to know info but may not apply to you
Visit our Water Leak Sensor 1 support page on our website, for the latest installation guides, additional resources, information and videos by visiting:
Your Water Leak Sensor 1 connects to the internet via a YoLink hub, and it does not connect directly to your WiFi or local network. In order for remote access to the device from the app, and for full functionality, a hub is required. This guide assumes the YoLink app has been installed on your smartphone, and a YoLink hub is installed and online (or your location, apartment, condo, etcetera, is already served by a YoLink wireless network).

In the Box 

  • Water Leak Sensor 1 
  • Quick Start Guide
  • 2 x  A  A  A Batteries (Installed) 

Get to Know your Water Leak Sensor

Water Leak Sensor Diagram Front has Alert LED with Electrodes (Water Detector), and back has Electrodes (Water Detector), a Status LED, SET Button, and Sensor Foot / Battery Compartment Screw Protector (4)

LED & Beep Behaviors

LED & Beep Behaviors Colors Diagram

Alert LED

Alert LED

Power Up

Before you can use your Water Leak Sensor 1, it must be turned on. (Batteries have been pre-installed.) Press the SET button briefly, until the LED flashes red then green (which indicates it has turned on and connected to a hub and the cloud).
Back of Water Leak Sensor with SET Button to press

Install the App

If you are new to YoLink, please install the app on your phone or tablet, if you have not already. Otherwise, please proceed to the next section.

Google YoLink App

Apple YoLink App


Open the app and tap Sign up for an account. You will be required to provide a username and a password. Follow the instructions, to set up a new account. Allow notifications, when prompted.

You will immediately receive a welcome email from with some helpful information. Please mark the domain as safe, to ensure you receive important messages in the future.

Log in to the app using your new username and password.

The app opens to the Favorite screen. This is where your favorite devices and scenes will be shown. You can organize your devices by room, in the Rooms screen, later. 

Add Your Water Leak Sensor 1 to the App

1. Tap Add Device (if shown) or tap the scanner icon:

2. Approve access to your phone’s camera, if requested. A viewfinder will be shown on the app.

Image of QR Code at back of Water Leak Sensor 1

3. Hold the phone over the QR code so that the code appears in the viewfinder. If successful, the Add Device screen will be displayed.

4. You can change the device name and assign it to a room later. Tap Bind device.
5. If successful, the screen will appear as shown. Tap Done
Success app screenshot of binding water leak sensor 1


Sensor location considerations: Before placing and setting up your Water Leak Sensor 1, consider the following important factors:
1. The Water Leak Sensor 1 is intended for indoor use, only. It should only be used in indoor environments and within the temperature and humidity ranges as specified in the product listing and product support page on our website.
2. While the Water Leak Sensor 1 is waterproof, it should not be used where it will always be in water or where it may frequently be submerged in water. If water level monitoring is required, consider our Water Level Monitoring Sensor.
3. The Water Leak Sensor 1 has water-sensitive probes or electrodes on both the top and bottom. When water is on or touches any pair of electrodes, this creates an electrical “short circuit” between the electrodes, and the sensor responds with a water leak alert. The top of the sensor is identified by a cupped area with one pair of electrodes. This cupped area is ideal for catching dripping water from above, such as under a sink. The bottom of the sensor has two pairs of electrodes. These are optimized for detecting water that pools or floods below the sensor. (See the next section)
Water Leak Sensor 1 Diagram
4. When determining the location and quantity of sensors required for your applications, consider the types of leaks or flooding that is expected. For example is the water coming from water overflowing, like a sink, toilet, or tub? Is it coming from a leak within an appliance, like a dishwasher? Is it coming from a loose or broken plumbing fitting, like on a laundry machine or ice maker water line? Generally, every location where water goes into or leaves an appliance, where there is a fitting or connection between two pipes, or fixtures, between a hose and a hose connection, and at every faucet or fixture where water comes out, is a potential leak location.
5. Consider how water may flow and pool or collect if there is a leak at each possible leak location. Consider the slope of the floor or the surface that water may drip onto. A leak at a sink cleanout will result in water directly below the sink, and this water may run towards the front of the vanity or cabinetry or to the back, draining into the base of the cabinetry (only appearing on the floor after a significant leak has occurred). Floors with drains, like in a mechanical room or near a water heater, are intentionally sloped down to the drain. Floors in older homes or where settling has occurred can also result in a slope. Take advantage of any slope in the floor by placing the leak sensor at the bottom of the slope or in the path of the water flowing down the slope. A marble, toy ball, or similar object can be used to check the floor's level, or you may consider pouring a small amount of water on the floor or surface where a leak is possible, to see how the water may flow and pool up.
6. Additional leak sensors can be added if you wish to protect a large region, or you can consider the Water Leak Sensor 2, our rope style leak sensor, that allows for creating larger water detection regions, with the use of additional cables.
7. Avoid locations where the sensor may be moved or disturbed by people or pets. Avoid locations in traffic areas where it may be kicked or stepped on, etc.
Applications (locations and placement) for the Water Leak Sensor 1 are many, and they can not all be covered in this guide. The following application examples cover the most popular ones for the WLS1, as well as for other YoLink water sensors. If your application is unique or if you are unsure where to place your sensor, please contact us!

Common Leak Sensor Application Examples


For external water leaks, place near the toilet, at the rear. Consider the Water Leak Sensor 4 MoveAlert, if the sensor may be kicked or moved. Also, consider the Water Leak Sensor 2, our rope style water sensor, that can be used to detect leaks from the toilet as well as an adjacent sink, tub or shower. For internal water leaks, consider our Water Level Monitoring Sensor (with float switch).


For vanity or enclosed style sinks, place the leak sensor under the P-Trap, otherwise at a location where leaking water may gather. For multiple sinks, place a sensor below each sink. For open or pedestal style sinks, place the sensor on the floor, near the wall, below the sink. Consider the Water Leak Sensor 4 MoveAlert, if the sensor may be kicked or moved. Also, consider the Water Leak Sensor 2, our rope style water sensor, that can be used to detect leaks from the toilet as well as an adjacent sink, tub or shower.


The sensor can be placed on the floor in front of the dishwasher, but this location may be subjected to being knocked out of place, in high traffic areas. Consider the Water Leak Sensor 4 MoveAlert, to protect against this. If the appliance can be moved out, placing one or a second sensor underneath the washer is ideal. Consider the cold and hot water line, and the drain hose connections, as likely locations for a leak. If keeping the sensor out of view is desired, consider the Water Leak Sensor 2, that can be discretely placed on the floor at the front of the dishwasher, and/or underneath the washer. And it may be possible, with extension ropes, to also detect leaks in an adjacent sink area.

Icemakers, Refrigerators 

Icemakers, and refrigerators with water and/or icemaker features (with a water line in) are subject to water leaks, which typically occur at the rear of the appliance. Ideally, place the leak sensor behind the appliance and under the water connection. The Water Leak Sensor 2 can also be used for this application, and it is often possible to place the sensor body at a more accessible location, such as in the cabinet above the fridge. This can make battery replacement more convenient, and it may be more appropriate for built-in appliances. Extension ropes/cables are available for this purpose.

Laundry Machines

Laundry machine water leaks are common at the front as well as the rear of the appliance. Depending on floor slope (if applicable) and the amount of water, placing one sensor near the rear of the appliance may be sufficient, otherwise, consider placing one at the front and rear. Also, consider the Water Leak Sensor 2, with extension ropes, that can encircle the machine with the water-sensitive ropes. Consider our Water Leak Sensor 3, our probe type water sensor, for use with drain pipes, for early-warning of backups, otherwise, a sensor on the floor at the drain pipe location is suggested as an alternative (to the WLS3).

Water Heaters

Water heater leaks are frequently detected at the base of the water heater, but the location is often on a floor that has a slight slope to a floor drain. When placing the sensor, factor-in the path water may take, as it runs to the low point of the floor. Or, consider the  Water Leak Sensor 2. The Water Leak Sensor 2’s rope(s) can be used to encircle the base of the water heater, making it less likely that a small leak is not detected promptly.

Sump Pumps

For sumps that are typically dry, placing the sensor in the sump is ideal. If a small, acceptable, amount of water may be present, the sensor should be placed on the floor, near the edge of the sump. This is not to be considered early-warning. In this case, consider the  Water Leak Sensor 2. The Water Leak Sensor 2’s rope(s) can be used to encircle the sump. Also, consider the Water Level Monitoring Sensor (with float switch), for placement within the sump.


The Water Leak Sensor 1 can be used to detect water condensation overflow or build-up, depending on the air conditioner type and method of condensate discharge. For pans or trays, the sensor can be placed in the pan/tray, if it is normally dry. Or, place the sensor on the floor near the air conditioner. Otherwise, consider our  Water Leak Sensor 3, our probe type water sensor, or the Water Level Monitoring Sensor (with float switch) for faster detection, as they can be placed in the condensate overflow pan or in the discharge pipe.


Water leaks from fish tanks can result in extensive damage. Typical aquarium applications include simply placing the sensor on the floor, behind the tank. If there is filtration or pump equipment located in the tank stand, for example, additional sensors may be required here. For confined space water detection, consider the  Water Leak Sensor 2. For early warning, consider our Water Level Monitoring Sensor (with float switch), to monitor water levels in the tank and/or sump.


Consider our  Water Leak Sensor 2, a rope style sensor, that may be more appropriate for detection of leaks in roofs. Otherwise, if detecting leaks at locations prone to leaks, place the Water Leak Sensor 1 at these locations and/or where water gathers or pools up. The use of trays or pans (even large baking pans/trays), placed below areas at risk of leaks, can be used to gather leaking water, allowing a sensor placed in the tray to detect leaks as quickly as possible.
Please refer to device environmental operating range information. Use this device outside the recommended ranges at your own risk


Place the leak sensor

After you have selected a location for the leak sensor, simply place it on the floor or surface, with the cupped part of the sensor facing up.

Test the leak sensor

Functionally test each sensor. A common way to test the Water Leak Sensor 1 is by touching any pair of electrodes with a damp paper towel, but you may find that you can activate the sensor by bridging a pair of electrodes with your thumb or finger. If you choose to pour water on the sensor or on the floor, be sure to fully dry off the sensor after testing. With the app in hand, and the particular leak sensor in view in the app, test your Water Leak Sensor 1. After the sensor has responded properly (and you’ve dried it off, if applicable), confirm the sensor is shown to be “Normal” in the app.

App Functions: Device Screen

In the app, tap on your Water Leak Sensor 1 icon. Your Water Leak Sensor 1 main screen should be similar to the one shown below.

Water Leak Sensor Diagram


Tap the three dots (in the upper right corner) to open the Water Leak Sensor 1 Details screen. Your Water Leak Sensor 1 screen should be similar to the one shown below.

Water Leak Sensor Diagram


App Functions: Alert Settings Screen

Water Leak Sensor Alert

App Functions: Alarm Strategy Screen

You can set up notifications in Alarm Strategy settings, make sure you have enabled App, Email, SMS notification from the app->Menu->Settings->Account Settings->Advanced Settings, and verified your email address and added your phone number in the app.

Water Leak Sensor Screenshot

 App Functions: Automation

The Water Leak Sensor 1 can be set up as a condition in an automation. For example, you can automatically turn on a fan if the sensor detects a high temperature. This example is shown below. The automation also sends a custom notification (via app push notification, email SMS, or SpeakerHub broadcast) reminding you the sensor detects high or low temperature or humidity.


Water Leak Sensor 1 Automation

Control D2D

YoLink Control-D2D is our unique device to device control technology. Using YoLink Control-D2D, YoLink devices can be controlled without the Hub or an internet connection. (Use of YoLink Control-D2D is optional; you can use the Automation feature in the app OR use YoLink Control, but YoLink Control-D2D offers the benefit of operation without the Hub or internet connection.) One device controls another, directly. A device that sends out commands is called the controller. A device that receives the commands is called the responder. Examples of a controller are a Water Leak Sensor, while examples of a responder are a Siren or the Smart Motorized Valve. The following instructions uses pairing your Water Leak Sensor 1 with a YoLink Valve Controller as example.

Set button on back of water leak sensor 1

1. To configure your Water Leak Sensor 1 as a controller, Press and hold the SET button for 5-10 seconds until the LED quickly blinks green, then, release the button.

2. To configure a Valve Controller as the responder, close the valve using SET button or via YoLink app (verify the valve is shown to be Closed on the app).Press and hold the SET button for 5-10 seconds until the LED quickly blinks green, then, release the button.

Setting Water Valve Controller

3. Upon pairing, the LED will stop blinking (this may happen after only blinking two or three times).

When the Water Leak Sensor detects water, the Valve Controller will now immediately close the valve. The valve will remain closed until opened via the app or using the SET button; the restoral of the Water Leak Sensor to normal (no water detected) does not open the valve.

More advanced sequences, controlling multiple outputs (e.g.close valve and activate siren) are available via the YoLink app. To take a look at the smart valve solutions we offer, please visit our Smart Water Solutions page.

3rd Party Services

You can use the Water Leak Sensor 1 to trigger Alexa routines. You must have the Alexa app installed, the YoLink skill installed and connected to your YoLink app account.

1. Create a new routine in the Alexa app.

2. In the When This Happens section, select Smart Home.

3. Find your water leak sensor and select it.

4. Alexa integrates the Water Leak Sensor 1 as a contact sensor, so the available sensor states are "Closed" or "Open" like a set of electrical contacts on a relay, button or switch. The default state is Open. Leave on or change to Closed, then tap Next.

5. For Add Action, tap the + button, then Smart Home and select your device (siren, valve controller, etc.), tap Next.

6. For a valve controller, for example, select On, then tap Next.

7. Review your settings, then tap Save.

⚠️ Always functionally test your new automations and routines!

You can use the Water Leak Sensor 1 to trigger IFTTT applets. You must have the IFTTT app installed, the YoLink service installed and connected to your YoLink app account.

🤔 Please note, is a paid service, typically offering a limited number of free applets.

1. Create a new applet in the IFTTT app.

2. For the If This section, search and select the YoLink service.

3. Tap Leak Sensor.

4. In the Device drop-down box, select your Water Leak Sensor 1, tap Done.

5. Tap Create Trigger.

6. Tap Continue to save your settings.

7. Review your applet settings, if they are correct tap Finish.

⚠️ Always functionally test your new automations and routines!

Battery Replacement

Tools Required :

Small Phillips Screwdriver

Small Phillips Screwdriver


Tweezers or Needle/Pin or Tack

Tweezers or Needle/Pin or Tack



1. To maintain the watertight design of your Water Leak Sensor, use extreme care and follow the battery replacement instructions closely

2. Do not mix old and new batteries

3. Make sure that the bottom shell and sealed rubber pads are tightly secured. Otherwise, the entry of water into the sensor may cause severe damage.

1. Use a pin or needle, tack, or tweezers to remove the four sealed rubber pads at the base of the device

Replacing Water Leak Sensor 1 Batteries

2. Use a screwdriver to loosen the screws at the base of the device and remove the base. Use care to retain the screws in the base, or carefully set them aside

Replacing Water Leak Sensor 1 Batteries

3. Remove the two old batteries

Replacing Water Leak Sensor 1 Batteries

4. Install two new AAA batteries

Replacing Water Leak Sensor 1 Batteries

5. Close and secure the base by reinstalling and tightening the four screws

Changing batteries in Water Leak Sensor 1

6. Reattach the four sealing rubber pads

Changing batteries in Water Leak Sensor 1

7. Press the SET button, and observe the Status LED blinks red then green, indicating it is online. 

⚠️ After replacing the batteries, it is a good idea to test the sensor.


Voltage: 3V DC (2-alkaline non-rechargeable AAA batteries)

IP Rating: IP68

Dimensions: 2.44 × 2.44 × 0.93 inches (62 × 62 × 23.5 millimeters, L×W×D)

Environment: Working Temperature: 32°F - 122°F (0°C - 50°C) Working Humidity: ≤ 100%RH (non-condensing)

Factory Reset

When directed by customer support, and/or as an attempt to resolve a problem with your Water Leak Sensor 1, it may be necessary to perform a factory reset. Factory resetting your Water Leak Sensor 1 returns it to the factory default programming and settings.

This is a simple process: Hold the SET Button for 20 to 30 seconds, until the LED blinks red and green alternately, then release the button.

Water Leak Sensor 1

Factory reset is complete when the LED stops flashing.

Firmware Updates

Your YoLink products are frequently being improved, with new features and functions added over time. It is periodically necessary to make changes to your device firmware. For optimal performance of your device, and to give you access to any improvements made to your device model, these firmware updates should be installed (added to your device) when they become available.

In the Detail screen of your device, you will see the Firmware section, as shown in the image below. A firmware update is available if it says “#### ready now” (where #### is a four-digit combination of letters and/or numbers).

Firmware updates

Firmware is like settings in your Water Leak Sensor 1 that define the overall operations of the Water Leak Sensor 1. These settings are added to the Water Leak Sensor 1 when it is manufactured, and they are periodically updated, as needed, to add improvements, new features, new integrations, etc, to your Water Leak Sensor 1, as they become available. Tap in the Firmware area to start the update. The Water Leak Sensor 1 will update automatically, indicating the progress by percentage-complete. You may use your Water Leak Sensor 1 during the update process, as the update is performed “in the background”. You may see the LED slowly blink green during the update, and the update may continue for several minutes beyond the LED turning off.

🤔 If you experience incomplete firmware updates, please update only one device at a time. If this does not resolve the problem, please contact our customer support department!

Troubleshooting Problem: Sensor is Offline

a) Sensor has not been turned on. Press the Set button to turn on the sensor.

b) Batteries are dead. Replace the batteries. (See above for instructions on how to replace batteries) If this does not resolve the issue, please contact our customer support department.

We recommend checking for and performing any available firmware updates before contacting customer support. See Firmware Updates. 


For optimal performance and lifetime of your Water Leak Sensor 1, please adhere to the following warnings:

  • When replacing the batteries, only use new alkaline or lithium non-rechargeable batteries.
  • Do not use zinc blend batteries.
  • Do not mix old and new batteries.
  • Adhere to the battery manufacturer’s safety and disposal or recycling instructions.
  • Please contact Customer Support before attempting to repair, disassemble, or modify your Water Leak Sensor 1, any of which can permanently damage your Water Leak Sensor 1 and void the warranty.


2 Year Limited Electrical Warranty

YoSmart Inc. warrants to the original user (“customer”) of this product that it will be free from defects in materials and workmanship, under normal use, for 2 years from the date of purchase. This warranty does not apply to devices that have been improperly installed, modified, put to a use other than designed, or subjected to acts of God (such as floods, lightning, earthquakes, etc.). This warranty does not cover neglected or abused products. This warranty is limited to the repair or replacement of the device, only, at YoSmart's sole discretion. YoSmart will NOT be liable for the cost of installing, removing, nor reinstalling this product, nor direct, indirect, or consequential damages to persons or property resultng from the use of this product. This warranty only covers the cost of replacement parts or replacement units, it does not cover shipping & handling fees. The customer must provide proof of purchase, in the form of the original purchase invoice or order number. The purchase must have been made from an authorized seller.

To implement this warranty please contact us by one of the methods listed on the Contact Us page of this user guide.

FCC Statement

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. Any Changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment.

Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

- Reorient or relocate the receiving antenna.

- Increase the separation between the equipment and receiver.

- Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

- Consult the dealer or an experienced radio/TV technician for help.

The device has been evaluated to meet general RF exposure requirement. The device can be used in portable exposure condition without restriction.

Contact Us

We are here for you, if you ever need any assistance installing, setting up or using a YoLink app or product!

Need help? For fastest service, please email us 24/7 at

Or call us at 831-292-4831 (US phone support hours: Monday - Friday, 9AM to 5PM Pacific)

You can also find additional support and ways to contact us at:

Finally, if you have any feedback or suggestions for us, please email us at

Thank you for trusting YoLink!

YoLink Customer Support