# Soil moisture sensor installation
## **Before installation – probe hydration**
The WATERMARK soil moisture probe (model 200ss) contains air when new and must be fully hydrated before installation. **Do not install a dry probe, as this will result in incorrect readings**. Proper hydration replaces the air in the sensor’s porous material with water, ensuring accurate performance. This preparation process is essential and must be followed carefully. After completing the hydration cycle once, the probe is ready for use. Always install a fully soaked probe.
Follow the hydration procedure below:
1. Submerge the probe **less than halfway** in water for **30 minutes**.\
2. Allow it to **dry for 10 hours**.
3. Submerge it again **less than halfway** for **30 minutes**, then **dry for 10 hours**.
4. Repeat a third cycle: **30-minute submersion (less than halfway)** + **10-hour drying**.
5. Finally, fully immerse the probe in water for **8 hours** (air bubbles may be visible as the remaining air escapes).\
Once these steps are completed, the probe is fully hydrated and ready for installation.
## **Installation**
{% hint style="danger" %}
Soil moisture and temperature probe cables must be routed inside a PVC pipe with an internal diameter of **at least 23 mm**. Cables placed directly in soil may be damaged by rodents.
{% endhint %}
1. Dig a hole at the intended measurement depth.
2. Mix the excavated soil with water until it reaches a **thick, honey-like consistency**.
3. Pour some of this slurry into the bottom of the hole.
4. Place the hydrated probe at the bottom, ensuring **direct contact** between the probe and the soil.
5. Fill the remaining space in the hole with the prepared soil slurry to eliminate air gaps and ensure proper sensor-to-soil contact.
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