How to Detect Leaks in Household Water Filters or Their Components
Leak testing is crucial for the manufacturing of water purification systems. Traditional methods, however, carry the risk of errors and unnecessary scrap. More precise leak detection methods ensure product quality and reduce complaints and costs.
Application
The water purification unit typically consists of 3 to 5 cylindrical filters connected with quick-release couplings and plastic hoses. All components, including some electronic parts, are housed in a cabinet. This document describes the leak testing of the assembled water purification device or its components using INFICON leak detectors.
Traditional Methods
In current industry practice, water purifiers are often tested for leaks using a water bath or soap spray. These tests are generally based on the subjective criterion of "no bubbles within X seconds," which is based on historical precedents rather than industry standards. A commonly observed guideline is "no bubbles in 15 to 30 seconds at 4 bar," which corresponds to leak rates:
Estimated Leak Rates Based on Bubble Size
| BUBBLE SIZE | LEAK RATE |
|---|---|
| 1.0 mm | 1.7x10E-5 to 3.5x10E-5 mbarl/s |
| 2.5 mm | 2.7x10E-4 to 5.4x10E-4 mbarl/s |
The leak rate limits applicable to water purification systems often approach the sensitivity required for HVAC/R industry gas leaks (1x10E-4 mbarl/s). With soap spray tests, the acceptance threshold is typically "no visible bubbles during a test time of 2-5 minutes," which remains a subjective and time-consuming method. These results underscore the need for more standardized, objective leak testing procedures that are both practical and cost-effective.
Typical Procedure
The components are pressurized with water and placed on a piece of paper that indicates the presence of a leak. This initial test usually takes about 15 minutes. For assembled products, leak testing is performed by pressurizing the system with air at 4-5 bar, followed by immersion in a water bath or application of soap water.
Approximately 10-15 connections are tested. A foamed soap solution is applied to the connections and left for 2-5 minutes (de-foaming). Subsequently, each joint is visually inspected. The typical test time per joint is 5 to 15 seconds. The disadvantages of using soap are:
- Possibly missed leaks - Large leaks blow away the soap film, small ones are hard to detect, and both can go unnoticed.
- Over-quality and cost consequences - Rejecting parts that are functionally leak-tight causes unnecessary costs.
- Limited visual access - An operator can hardly inspect all 10-15 joints per unit reliably, leading to undetected leaks.
- Space requirements - Since the soap needs 2-5 minutes to rest before inspection, additional space is needed to store the units during this waiting period.
- Production bottlenecks - Waiting times cause backlogs and tie up capital.
The INFICON Solution
This method uses forming gas as the test gas. To ensure optimal gas concentration in the chamber, it is important to evacuate the air before filling or to fill through one opening while simultaneously evacuating through another opening at the opposite end. Simple filling at 4 bar is possible but can lead to dilution and reduced sensitivity. Due to complex internal geometries, not all products are suitable for the push-in technique. The TGF11 gas filling unit is a standalone device for trouble-free filling of test parts with gas.
Once filling is complete, the leak test can begin. The core of the solution is the Sentrac hydrogen leak detector as a single unit for manual leak detection or in combination with the AP29ECO sampling unit for automatic or semi-automatic leak detection. Controlled by Sentrac, the AP29ECO allows for an accumulation time before analyzing the air in the cabinet. If the gas concentration exceeds the rejection threshold, the Sentrac triggers an alarm. The operator checks each connection with the hand probe in about one second. High sensitivity and automatic mode are recommended to reliably detect leaks. After repair, the test gas should be released in a controlled manner to avoid contaminating the test area. If testing is performed on a moving conveyor belt, separate evacuation systems may be required. The TGF11 also supports evacuation to effectively control gas release.
Advantages of Trace Gas Leak Detection
- Quick localization of the leak position
- No interpretation of leak size by the operator - precise measurement
- Only leaks exceeding the rejection limit are repaired
- No time wasted on cleanup or drying after the test
- All leaks detected, even in hard-to-reach areas
- No stacking of waiting products saves space and capital
How We Do It
Testing a water purifier for leaks using hydrogen test gas is an effective method to repair only those parts that are leaking above the rejection limit.
Evacuate the Water Purifier
This allows for correct filling with test gas and ensures accurate test results.
Fill the Water Purifier with Trace Gas
To ensure maximum concentration inside.
Detect Leaks
Use the sniffing probe to locate leaks at the relevant connections.
