Monitor four essential water quality parameters with the Milwaukee MW803 MAX Waterproof 4-in-1 Digital Water Quality Tester.

Designed for convenience, accuracy and versatility, this professional pocket-sized instrument measures pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature using one compact device.

The Milwaukee MW803 MAX is an excellent choice for aquarium owners, aquaculture professionals, hydroponic growers, horticultural businesses and water quality specialists looking for a convenient all-in-one testing solution.

Featuring a waterproof IP65-rated housing, automatic temperature compensation (ATC), automatic calibration and a replaceable combination probe, the MW803 MAX provides reliable measurements across a wide range of water testing applications.

Its large dual-level LCD displays pH, EC or TDS readings alongside temperature, allowing you to monitor important water quality parameters quickly and easily.

With a pH measurement accuracy of ±0.05 pH, the MW803 MAX combines professional measurement performance with straightforward operation.

Key Features & Benefits

• 4-in-1 Water Quality Testing: Measures pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature using one instrument.

• High-Accuracy pH Measurement: Provides ±0.05 pH accuracy with a resolution of 0.01 pH.

• Electrical Conductivity Measurement: Measures EC from 0 to 3999 µS/cm, making it suitable for low-to-medium conductivity applications.

• TDS Measurement: Measures total dissolved solids from 0 to 2000 ppm.

• Automatic Temperature Compensation: Automatically compensates pH and conductivity measurements for temperature variations.

• Waterproof IP65 Construction: Designed to withstand water exposure and splashes during routine testing.

• Replaceable Combination Probe: Features the Milwaukee MI60P replacement probe, extending the useful working life of the instrument.

• Automatic Calibration: Simple automatic one- or two-point pH calibration and one-point EC calibration.

• Multiple Calibration Points: Recognises five memorised pH calibration buffer values.

• Dual-Level LCD Display: Shows measurement readings alongside water temperature.

• Stability Indicator: Helps identify when measurements have stabilised.

• Hold Function: Freezes displayed readings for convenient recording.

• Selectable TDS Conversion Factor: Allows the TDS conversion scale to be adjusted to suit different applications.

• Compact & Lightweight: Portable pocket-sized design weighing approximately 100 g.

• Long Battery Life: Approximately 100 hours of continuous operation.

Ideal Applications

The Milwaukee MW803 MAX is suitable for a wide range of water quality monitoring applications.

Aquariums & Fish Tanks

Monitor pH, conductivity, TDS and temperature to help maintain stable aquarium water conditions.

Regular testing helps identify changes in water chemistry and provides a better understanding of overall aquarium water quality.

The ability to monitor four parameters using one instrument makes the MW803 MAX a useful addition to any serious aquarium maintenance setup.

Aquaculture & Fish Farming

Water quality monitoring is essential in commercial fish farming and aquaculture operations.

The MW803 MAX allows operators to monitor pH, conductivity, dissolved solids and temperature in fish tanks, hatcheries and recirculating aquaculture systems (RAS).

Regular measurements help identify changes in water conditions and support effective water quality management.

Hydroponics

Electrical conductivity and pH are two particularly important parameters in hydroponic growing systems.

The MW803 MAX allows growers to monitor nutrient solution pH and EC while also checking temperature and estimated TDS.

This makes it a practical all-in-one instrument for monitoring hydroponic nutrient solutions and maintaining consistent growing conditions.

Horticulture & Agriculture

Monitor irrigation water, nutrient solutions and other agricultural water samples.

The combination of pH, EC, TDS and temperature measurements provides useful information for managing growing environments.

Koi Ponds & Garden Ponds

Monitor important water parameters to help maintain suitable conditions for fish and aquatic life.

Water Treatment & Environmental Monitoring

Suitable for routine water quality checks in water treatment applications, environmental testing and general industrial water monitoring.

Understanding the Four Measurements

The Milwaukee MW803 MAX combines four important water quality measurements in one instrument.

1. pH – Acidity & Alkalinity

pH measures how acidic or alkaline water is.

Monitoring pH is important in aquariums, aquaculture and hydroponics because changing pH conditions can influence aquatic organisms, biological processes and nutrient availability.

Measurement range: 0.00–14.00 pH.

2. EC – Electrical Conductivity

Electrical conductivity measures the ability of water to conduct electricity, which is influenced by the concentration of dissolved ions.

EC is particularly useful in hydroponics and aquaculture for monitoring changes in dissolved ionic content.

Measurement range: 0–3999 µS/cm.

3. TDS – Total Dissolved Solids

TDS estimates the concentration of dissolved substances in water, typically displayed in parts per million (ppm).

The MW803 MAX calculates TDS from its conductivity measurement using a selectable conversion factor.

Measurement range: 0–2000 ppm.

4. Temperature

Water temperature is an important parameter in aquatic environments and hydroponic growing systems.

The MW803 MAX measures temperature and displays it alongside the selected pH, EC or TDS reading.

Measurement range: 0.0–50.0°C.

Automatic Temperature Compensation (ATC)

Temperature can influence both pH electrode response and electrical conductivity measurements.

The Milwaukee MW803 MAX incorporates automatic temperature compensation to adjust measurements according to the temperature of the sample.

An exposed temperature sensor positioned close to the measurement probes provides a fast response and helps improve temperature-compensated readings.

The temperature is displayed on the secondary LCD, allowing you to monitor both measurements simultaneously.

Replaceable Milwaukee MI60P Combination Probe

One of the major advantages of the Milwaukee MW803 MAX is its replaceable MI60P combination probe.

The probe incorporates the sensing components required for pH, conductivity and temperature measurement.

The pH electrode uses a double-junction design, helping provide reliable performance and reducing routine maintenance requirements.

The replaceable probe offers several advantages:

• Extends the useful working life of the instrument.

• Allows replacement of worn or damaged sensing components.

• Avoids the need to replace the complete tester when the probe deteriorates.

• Provides a more economical long-term solution for regular water testing.

The replacement probe is the Milwaukee MI60P, compatible with both the MW803 MAX and MW804 MAX.

Technical Specifications

Specification	Details
Brand	Milwaukee Instruments
Model	MW803 MAX
Measurement Parameters	pH, EC, TDS & Temperature
pH Measurement Range	0.00–14.00 pH
pH Resolution	0.01 pH
pH Accuracy	±0.05 pH
EC Measurement Range	0–3999 µS/cm
EC Resolution	1 µS/cm
EC Accuracy	±2% Full Scale
TDS Measurement Range	0–2000 ppm
TDS Resolution	1 ppm
TDS Accuracy	±2% Full Scale
TDS Conversion Factor	Adjustable, 0.45–1.00
Temperature Range	0.0–50.0°C / 32.0–122.0°F
Temperature Resolution	0.1°C / 0.1°F
Temperature Accuracy	±0.5°C / ±1°F
Temperature Compensation	Automatic (ATC)
Temperature Compensation Coefficient	Adjustable, 0.0–2.4%/°C
pH Calibration	Automatic, 1- or 2-point
EC Calibration	Automatic, 1-point
pH Calibration Buffers	pH 4.01, 6.86, 7.01, 9.18 and 10.01
EC Calibration Solution	1413 µS/cm
Probe	Milwaukee MI60P
Probe Type	Replaceable combination probe
Waterproof Rating	IP65
Display	Dual-level LCD
Stability Indicator	Yes
Hold Function	Yes
Operating Temperature	0–50°C
Maximum Relative Humidity	100%
Battery Type	4 × 1.5V LR44 / A76
Battery Life	Approximately 100 hours
Automatic Power-Off	After 8 minutes of inactivity
Dimensions	Approximately 200 × 38 mm
Weight	Approximately 100 g

Easy Automatic Calibration

The Milwaukee MW803 MAX features automatic calibration to help maintain measurement accuracy.

pH Calibration

The instrument supports automatic one- or two-point pH calibration.

It recognises five memorised calibration buffer values:

• pH 4.01

• pH 6.86

• pH 7.01

• pH 9.18

• pH 10.01

Two-point calibration is recommended for greater accuracy across your intended measurement range.

EC Calibration

The EC measurement can be calibrated using a suitable conductivity calibration solution.

For the MW803 MAX, the recommended calibration solution is:

1413 µS/cm Conductivity Calibration Solution.

The instrument automatically recognises the calibration point and completes the calibration process.

Understanding EC and TDS Conversion

Although EC and TDS are closely related, they are different measurements.

EC measures electrical conductivity, while TDS estimates the concentration of dissolved substances in water.

The MW803 MAX converts EC measurements into estimated TDS values using an adjustable conversion factor between 0.45 and 1.00.

Different conversion factors can produce different TDS readings from the same EC measurement.

This is particularly important in hydroponics and aquaculture, where different measurement scales may be used.

For consistent monitoring, always use the same conversion factor when comparing TDS readings over time.

Probe Maintenance & Care

Proper maintenance is essential for maintaining accurate measurements and extending the life of the MI60P combination probe.

We recommend:

• Store the pH electrode using Milwaukee MA9015 electrode storage solution.

• Never store the pH electrode in distilled or deionised water.

• Clean the probe regularly using suitable Milwaukee MA9016 cleaning solution.

• Rinse the probe with fresh water after every measurement.

• Avoid allowing nutrient solutions or mineral deposits to accumulate on the sensing surfaces.

• Calibrate after cleaning and whenever measurement performance needs checking.

• Replace the MI60P probe when it becomes damaged or its performance deteriorates.

• Keep the protective cap fitted when the tester is not in use.

Recommended Accessories

The following Milwaukee accessories are suitable for maintaining and calibrating the MW803 MAX:

• Milwaukee MI60P: Replacement combination pH/EC/TDS probe.

• Milwaukee MA9015: Electrode storage solution.

• Milwaukee MA9016: Electrode cleaning solution.

• Milwaukee MA9004: pH 4.01 calibration solution.

• Milwaukee MA9007: pH 7.01 calibration solution.

• Milwaukee MA9061: 1413 µS/cm conductivity calibration solution.

• Milwaukee M10031B: 1413 µS/cm calibration solution sachets.

• Milwaukee M10000B: Rinse solution sachets.

What's Included?

The standard Milwaukee MW803 MAX package includes:

• Milwaukee MW803 MAX 4-in-1 water quality tester.

• Replaceable MI60P combination probe.

• Protective probe cap.

• pH 4.01 calibration solution sachet.

• pH 7.01 calibration solution sachet.

• 1413 µS/cm conductivity calibration solution sachet.

• Four LR44 batteries.

• Instruction manual.

• Protective packaging.

Why Buy from GroAqua?

GroAqua supplies specialist water quality monitoring equipment for aquariums, aquaculture, hydroponics, horticulture and water treatment applications.

From everyday aquarium testing equipment to professional water monitoring instruments, we help customers find practical solutions for maintaining water quality.

The Milwaukee MW803 MAX is an excellent choice for anyone looking for a versatile, waterproof water quality tester capable of measuring four essential parameters in one compact instrument.

Order your Milwaukee MW803 MAX Waterproof 4-in-1 Water Quality Tester from GroAqua today.