Updated on January 3, 2024


Created on September 28, 2018

WADI Solar Disinfection System

WADI is a solar powered UV measurement device that determines when solar water disinfection (SODIS) occurs in PET bottles.

Developed By
  1. Helioz
Content Partners
  1. Centre for Affordable Water and Sanitation Technologies (CAWST)


Product Description

WADI is a device that measures radiation levels while water is placed under the sun in PET bottles. A happy smiley face in the display indicates the point at which the water has been in the sun long enough to kill bacteria.

Target SDGs

SDG 6: Clean Water and Sanitation

SDG 3: Good Health and Well-Being

Market Suggested Retail Price


Target Users (Target Impact Group)


Distributors / Implementing Organizations

Partner organisations like Getwater.io, The GoodWater Company. Also, Helioz has implemented projects with distributors and institutions.

Competitive Landscape

Direct competitors include Solvatten Solar Safe Water System.

Manufacturing/Building Method

WADI is manufactured by Helioz GmbH in Austria.

Intellectural Property Type


User Provision Model

User can purchase the product directly by contacting the manufacturers or through Amazon.

Distributions to Date Status

5000 units distributed as of 2013.

Deactivation mechanism

Solar UV radiation

Energy source


Manufacturer-specified water treatment rate (L/hr)

Once WADI and the nearby water has received sufficient UV radiation, the sad face will turn happy along with 4 constant progress bars.

Bacteria reduction

6 log

Virus reduction

3 log

Protozoa reduction


Heavy metals and/or arsenic reduction


Maximum recommended influent turbidity level (NTU)

30 NTU

Effluent turbidity levels (NTU)

Does not reduce turbidity

Safe water storage capacity (L)


Design Specifications

WADI continuously measures the sun’s radiation and compares these measurements with scientifically tested data. As soon as the incident UV-dose reaches that of the reference value stored in WADI, the device indicates happy face.

Product Schematics

Technical Support

Contact the manufacturer

Replacement Components

Not available


Minimum two years based on normal handling.

Manufacturer Specified Performance Parameters

WADI is free of any toxic substances and does not change the taste or appearance of water.

Vetted Performance Status

WADI has been tested in various independent laboratories across Europe, Africa and Asia. SODIS technology is developed by ETH Zurich.


Some basic safety measures are: 1. SODIS cannot be used for water with turbidity higher than 30NTU, polluted with water or harmful chemicals. 2. Only PET bottles are recommended for the use of WADI and SODIS. 3. Use of corrugated iron sheet for SODIS is highly recommended for better performance. 4. Regular cleaning of the solar cell and UV sensor is required to guarantee adequate energy supply and correct measurements.

Complementary Technical Systems

Methods or techniques to remove turbidity, metals and harmful chemicals from water.

Academic Research and References

“HELIOZ Projects,” Helioz.org. Available: https://www.helioz.org/en/helioz-projects

“Goal 6,” Sdgs.un.org. Available: https://sdgs.un.org/goals/goal6

CAWST, “WADI,” WADI. Available: https://www.hwts.info/products-technologies/36852e9b/wadi/technical-information

Chemical disinfection, “Of the WHO international scheme to evaluate household water treatment technologies,” Engineeringforchange.org. Available: https://www.engineeringforchange.org/wp-content/uploads/2018/06/WHO_2016_Results-of-Round-I.pdf

Evaluation methods. Household Water Treatment and Safe Storage Knowledge Base. Available: https://www.hwts.info/document/617db4cf/improvement-in-potable-water-through-solar-disinfection-sodis-with-uv-indicator-mini-evaluation-repo

Compliance with regulations

WADI follows the WHO Guidelines for safe drinking water.

Evaluation methods

Product evaluation: The evaluation of the WADI consisted of laboratory testing of the product’s performance against all three classes of pathogens. Testing followed requirements of the solar (UV and heat) technology-specific protocol. Following the manufacturer’s use instructions, three units (triplicate replicates) were evaluated for all three classes of pathogens in general and challenge test waters. A solar lamp was used to provide 550 W/m2 of simulated outdoor solar radiation in a laboratory setting. This irradiance corresponds to what would likely be observed between latitude 15° N and 35° N as well as 15° S and 35° S, where the majority of developing countries are located. Another evaluation report carried out by Agency of Cooperation and Research in Development (ACORD) in Uganda is available.

Other Information

By reducing the use of firewood to disinfect water, WADI leads to significant CO2 reductions.

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