When the ADT app reports a Water and Temperature Sensor as offline, the sensor cannot be heard by the control panel, and the likely causes are a flat battery, distance or interference, a damp or cold environment and a sensor that was reset. Start with the battery. These sensors sit in cold, damp places such as basements and crawl spaces, and cold shortens battery life, so a battery that lasted a year in a warm room may fail in a few months in a cold one. Replace it with a fresh battery of the type specified, and make sure the contacts are clean and dry.
The checks in more detail
Do not use rechargeable cells unless the instructions allow it. Then the radio link. A basement or crawl space is a poor place for radio: concrete, brick and earth block signals, and the panel upstairs may be a long way off. Check the signal in the app, and if it is weak, move the panel to a more central position or closer to the stairs, or consider placing the sensor where it can still protect the area but gets a better link, such as at the foot of the stairs. Keep it away from large metal objects, and avoid placing it right beside a router.
If the sensor reappears after a restart of the panel, the link was temporarily lost. Moisture and cold can damage electronics. Check that the sensor is not submerged and that its contacts are not corroded; a sensor that has been in water may need replacing. Avoid mounting it where the temperature falls well below its rated range. If it still shows offline with a fresh battery and a good signal, remove it from the system and add it again, following the pairing steps, and check its location. A leak sensor that is offline protects nothing, so do not leave it unresolved.
Contact ADT support with the model and serial number if it will not reconnect, and ask about replacement if it has been in water. Write the date you fit each battery on a small label inside the sensor cover, so that you know when it is due; sensors in cold, damp places should have their batteries changed yearly. If the sensor sits in a spot that floods, fit it on a short stand so the contacts, not the electronics, touch the water, which prolongs its life. After any repair of a leak, dry the sensor thoroughly before replacing it on the floor.
Differential
Likely causes of “ADT Water and Temperature Sensor is offline or unavailable”, and how to tell them apart
- 1
A battery drained by cold
What separates it The sensor goes offline in winter
How to confirm Fit a fresh battery
- 2
Moisture or corrosion
What separates it The sensor will not respond
How to confirm Dry it, clean contacts or replace it
- 3
A sensor reset by accident
What separates it It lost its pairing
How to confirm Remove and add it again
- 4
A temperature outside its range
What separates it It misbehaves in extreme cold
How to confirm Move it to a warmer spot
Before you touch a setting
Record this first — changing settings destroys the evidence
- The device's state in the app
- The battery or power
Try in this order
0 of 3 completedReplace the battery
ReversibleFresh and correct type.
Move the panel closer
ReversibleOr the sensor.
Check for moisture damage
ReversibleAnd corroded contacts.
Model-specific
What is true of this model and not of its siblings
- Cold batteries
- They drain faster in basements.
- Radio
- Concrete and earth block signals.
Stop boundary
When this stops being a self-service repair
- !If the problem persists after these steps, contact ADT with the device and system details
- !Do not disable a safety device
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Does the basement matter?+
Concrete blocks radio.
Can it get wet?+
Only as designed; check for damage.
Is it safe to leave offline?+
No, it protects nothing offline.