Hanna GroLine Waterproof pH/EC/TDS/Temperature Tester HI98131

The Hanna GroLine HI98131 Waterproof pH/EC/TDS/Temperature Tester gives hydroponic, greenhouse, aquaponic, and indoor growers four essential nutrient-solution measurements in one compact meter. Use it to monitor pH, electrical conductivity, total dissolved solids, and temperature without carrying several separate testers.

Its rugged waterproof housing is designed for humid growing environments and floats if accidentally dropped into a reservoir. Simple two-button operation, automatic temperature compensation, selectable TDS conversion factors, and Hanna Quick Cal compatibility make the HI98131 a practical choice for routine nutrient management.

Key Benefits

• Measures pH, EC, TDS, and temperature with one handheld tester
• Waterproof floating body designed for humid grow environments
• Automatic temperature compensation for pH and conductivity readings
• Selectable 0.5 and 0.7 EC-to-TDS conversion factors
• Replaceable HI73127 pH electrode extends the useful life of the meter
• Graphite EC/TDS sensor helps resist polarization and salt-related measurement errors
• Hanna Quick Cal mode calibrates pH and conductivity with one solution
• Stability indicator helps identify when a reading is ready to record
• HOLD function freezes the displayed measurement
• Battery Error Prevention System helps prevent unreliable low-power readings
• Automatic shutoff options conserve battery life

Measurement Specifications

Parameter	Range	Resolution	Accuracy
pH	0.00 to 14.00 pH	0.01 pH	±0.10 pH
EC	0.00 to 6.00 mS/cm	0.01 mS/cm	±2% full scale
TDS, 0.5 factor	0 to 3000 ppm	10 ppm	±2% full scale
TDS, 0.7 factor	0 to 3999 ppm	10 ppm	±2% full scale
Temperature	0.0 to 60.0°C / 32.0 to 140.0°F	0.1°C / 0.1°F	±0.5°C / ±1°F

Selectable TDS Conversion Factors

TDS is calculated from the meter’s conductivity measurement. The HI98131 allows growers to select the conversion factor used by their nutrient program:

• 0.5 conversion factor: An EC reading of 1.00 mS/cm is displayed as approximately 500 ppm.
• 0.7 conversion factor: An EC reading of 1.00 mS/cm is displayed as approximately 700 ppm.

Always verify which scale is used by your fertilizer manufacturer before comparing TDS readings with a feeding chart.

Calibration Options

The HI98131 supports several calibration methods:

• Automatic one- or two-point pH calibration using pH 4.01, 7.01, and 10.01 buffers
• Automatic one-point EC calibration at 1.41 or 5.00 mS/cm
• Combined pH and EC calibration using Hanna GroLine Quick Calibration Solution

Quick Cal offers a convenient routine calibration for compatible Hanna GroLine equipment. For maximum pH accuracy, particularly after cleaning or replacing the electrode, use a two-point calibration that brackets the expected nutrient-solution pH.

How to Take a Measurement

1. Remove the protective cap and rinse the sensors with distilled or deionized water.
2. Immerse the tester in the nutrient solution to the recommended level.
3. Gently stir the meter to remove trapped air bubbles.
4. Select pH, EC, or TDS using the meter controls.
5. Hold the tester steady until the stability indicator disappears.
6. Record the reading or press HOLD to freeze it on the display.
7. Rinse the sensors after testing and return the meter to proper storage.

Measure a well-mixed sample away from concentrated nutrient additions, pH adjusters, air stones, and dosing outlets.

Replaceable pH Electrode

The included HI73127 pH electrode can be replaced when its response becomes slow or calibration can no longer be completed successfully. This allows growers to replace the worn sensor instead of discarding the entire tester.

The electrode also features an extractable cloth junction. If readings become slow or unstable because the junction is dirty, approximately 3 mm or 1/8 inch of fresh cloth can be carefully pulled out and the contaminated portion trimmed away. Follow Hanna’s instructions and avoid pulling out an excessive amount.

Cleaning and Maintenance

Rinse the tester after every use to prevent fertilizer, organic residue, and mineral deposits from drying on the sensors. If readings begin to drift, stabilize slowly, or fail calibration, soak the sensing area in a compatible Hanna electrode cleaning solution before recalibrating.

Heavy organic additives and dirty nutrient solutions can coat the sensing surfaces or obstruct the pH reference junction. Routine rinsing and periodic cleaning help maintain dependable response times.

Proper Probe Storage

Keep the pH glass bulb hydrated in Hanna electrode storage solution. The protective cap contains an internal reservoir that can be filled with storage solution to keep the sensor moist between uses.

Never store the pH electrode in distilled or deionized water. Pure water can damage the reference system and shorten electrode life. If the electrode dries out, rehydrate it in storage solution before calibration and use.

Battery Protection

The meter displays its battery level at startup and includes a low-battery indicator. Hanna’s Battery Error Prevention System automatically shuts the tester down when battery power becomes too low to provide dependable measurements.

The selectable automatic shutoff can be set for 8 minutes, 60 minutes, or disabled.

What’s Included

• Hanna GroLine HI98131 combo tester
• Replaceable HI73127 pH electrode
• Electrode removal tool
• Hanna Quick Cal solution sachets
• Electrode cleaning solution sachet
• Storage cap
• Batteries
• Quality certificate
• Instruction manual

Recommended Accessories

For reliable long-term performance, pair the HI98131 with:

• Hanna GroLine Quick Calibration Solution
• Hanna GroLine pH 4.01 Calibration Buffer
• Hanna GroLine pH 7.01 Calibration Buffer
• Hanna GroLine Conductivity Standards
• Hanna General Purpose Cleaning Solution
• Hanna pH Probe Storage Solution
• Hanna HI73127 Replacement pH Electrode

Calibration, cleaning, and storage solutions should be replaced regularly and should never be poured back into their original containers after use.