Setting Up Your Blumat SensorsUpdated 2 months ago

Before You Install

Every Blumat sensor must be filled with water and soaked for 15 minutes before installation. The ceramic cone needs to be fully saturated to work correctly — a dry cone will not respond to soil moisture properly.

Your soil also needs to be pre-moistened before the sensor goes in. Installing into dry soil means the sensor has nothing to read and will open immediately, potentially overwatering.

Sensor Lengths: 5-Inch vs. 9-Inch

Blumat TROPF sensors come in two lengths, and the choice affects how your system behaves:

5-Inch Sensor

• Best for small pots or when monitoring surface moisture
• Responds quickly — short, frequent watering cycles
• Tight moisture control with minimal dryback

9-Inch Sensor

• Ideal for raised beds and large containers
• Can be installed at any depth between 5 and 9 inches
• Delivers broader moisture swings — larger drybacks between watering events
• The deeper the sensor, the more soil must dry before triggering a watering cycle

Use deeper sensors when longer watering intervals or deeper hydration is preferred. Use shallower sensors for fast, responsive cycling in upper soil zones.

Sensor Types: Standard vs. Preset

Standard Sensors

Standard sensors are manually calibrated using the hanging drip method. The goal is always to first find the hanging drip — the point where water just begins to drip from the 3mm line — and then adjust from there.

Method 1: Cap Dialing Before Installation

1. Connect the top of the sensor to a water supply
2. Find the hanging drip point on the dial
3. From the hanging drip, tighten clockwise ~¼ turn to close the sensor and set a drier set point
4. Soak the ceramic cone underwater
5. Assemble the sensor while submerged, then install into pre-moistened soil

Method 2: In-Soil Adjustment After Installation

1. Install and soak the sensor as normal
2. Find the hanging drip point while the sensor is in the container
3. Adjust based on current soil moisture: leave at hanging drip if moisture is right, loosen counterclockwise if too dry, tighten clockwise if too wet

Adjustment guide: Each 1/16 inch of turn = approximately 10 mbar. A full ¼ turn ≈ 60 mbar.

Preset Sensors

Preset sensors are color-coded and pre-adjusted for common pressure ranges — a fast, accurate starting point without manual calibration.

• Gold mark → calibrated for gravity systems (low pressure)
• Silver mark → calibrated for pressurized systems (higher pressure)

To set a preset sensor:

1. Do not remove the protective cap — it protects the setting from accidental changes
2. Use the adjustment key (included with your system) through the hole in the top of the cap
3. Align the sensor to the correct color mark for your system type
4. Install into pre-moistened soil
5. Allow 24–48 hours to stabilize and begin watering

After the sensor is active, you can fine-tune using the same principles as standard sensors: 1/16 inch counterclockwise = ~10 mbar wetter, 1/16 inch clockwise = ~10 mbar drier.

Understanding the Moisture Range

Blumat sensors are fully adjustable from very wet to very dry. Here's how to think about the range:

• Below 20 mbar: Exceeds field capacity — water may run out the bottom of containers. Not recommended for most potted plants.
• 40–60 mbar: Ideal for vegetative growth — consistently moist root zone for fast growth and nutrient uptake.
• 60–100 mbar: Better for flowering stages or crops that benefit from slightly drier conditions.
• Above 150 mbar: Soil can become hydrophobic, especially in peat-heavy mixes — water resistance increases and moisture no longer wicks evenly. Not recommended.
• 300 mbar: Permanent wilting point — most plants cannot recover from this level of dryness.

For most growers, 50–100 mbar is the sweet spot.

Sensor Placement

• Place the sensor 3–4 inches from the first distribution point (dripper, drip ring, or BluSoak tape)
• The drip point should be toward the center of the pot, not at the edge
• Too far from the distribution: sensor may not detect moisture → risk of overwatering
• Too close: sensor may respond too quickly → risk of underwatering

After Installation

Allow 24–48 hours for a newly installed sensor to stabilize before making adjustments. Newly transplanted plants may not immediately activate the sensor — especially if the root ball is small relative to the container. Spot-water the root ball with 200–500 mL of water if needed in the first few days until roots grow into the surrounding medium.