Sonoff WTS01 Waterproof Temperature Sensor

Sonoff WTS01 — Waterproof Temperature Probe

A waterproof probe you can drop directly into water — your water heater tank, an aquarium, a pool, a greenhouse. It plugs into a Sonoff TH Elite or Sonoff TH Origin, and that pair gives you live temperature readings on your phone plus automatic on/off control of whatever you’ve wired up.

The most common use: replace your water heater’s old mechanical thermostat. Stop heating water you don’t need.

Why people buy it

• Stop heating water 24/7. Drop the probe in your tank, pair with a TH Elite, set “off at 55°C, on at 45°C”. Your heater only runs when it actually needs to.
• Keep an aquarium / vivarium stable. Get alerts the moment temperature drifts outside your set range.
• Monitor your pool from the app. Especially useful if it’s somewhere you don’t visit daily (rooftop, village house).
• Greenhouse and germination control. Auto-turn heating mats on at night and off in the morning.

Key Features

• Fully waterproof — submerge it in water, no enclosure needed.
• Temperature range: -40°C to +115°C — covers anything from freezer to boiling water.
• Cable extension up to 25 m using a standard phone (RJ9) cable or Cat6 ethernet — for when the heater is far from where you want the switch.
• Live readings in the eWeLink app, refresh every few seconds.
• Pairs with Sonoff TH Elite (16A or 20A) or Sonoff TH Origin for automatic device control.
• RJ9 plug — same shape as an old phone-line connector.

💡 Pro Tip: Attach the probe directly to the side of your water heater tank (not in the water — touch the metal). Wrap it with insulation tape so it reads the tank surface temperature accurately. Then set the TH Elite to “off at 55°C, on at 45°C” — you’ll always have hot water and stop paying to overheat it.

⭐ Frequently Asked Questions

Does the probe work on its own?

No — it’s a sensor only, not a smart switch. It must be paired with a Sonoff TH Elite or TH Origin. The TH device is what reads from the probe, displays in the app, and turns devices on or off.

How long can I extend the cable?

Up to 25 meters using a phone cable (RJ9) or a regular Cat6 ethernet cable cut to the connector. Plenty for almost any water-heater setup.

Is it really waterproof?

Yes — the sensor tip is fully sealed. You can submerge it directly in water (fish tanks, water heater tanks, pools).

What’s the temperature range?

-40°C to +115°C. Covers anything from freezer monitoring up to hot water heaters and boilers.

Will it work with my existing temperature sensor or another brand?

No — Sonoff TH switches only work with Sonoff probes. Other brands use different plug shapes and signal types.

What if the temperature reading suddenly disappears?

Usually means the cable is loose or damaged at the RJ9 connector. Unplug, check the pins, plug it back in. If it still doesn’t work, the cable extension may have a break — try with the original short cable to rule out the extension.

Can it measure power consumption too?

No — this is temperature only. If you also want power monitoring on the same appliance, add a Sonoff S60 smart plug or use a smart breaker.

Easy to install?

Yes. The probe plugs into the TH Elite/Origin via RJ9 — same plug shape as a landline phone cable. Place the tip where you want to measure (in water, on the tank, in the room). No wiring required for the probe itself.