What kind of water should I use in my AES test chamber?

Resistivity: 0.05MΩ * cm to 6MΩ * cm      Conductivity: 20µS to 0.167µS TDS: 10 ppm to 0.083 ppm

AES Humidity Water Supply Requirements

Water is one of nature’s most powerful elements. It can build and destroy natural landforms. It can also ruin your environmental test chamber.

If your environmental test chamber uses water, you must pay attention to the quality of the water you are supplying to the test chamber. If the water is full of minerals, sediment builds up and clogs the test chamber systems. If the water is too clean or pure, it strips minerals from the metal as the water travels through the test chamber. It's essential to test the supply water that enters your environmental test chamber.

Purification Recommendations

Despite being made of corrosion-resistant materials, the humidity system in your chamber needs filtered water to function correctly.

Resistivity, conductivity, and total dissolved solids (TDS) are three benchmark indicators of water purity. The more conductive water is, the greater the number of dissolved compounds in the water.

Resistivity, conductivity, and TDS are low-fidelity measurements that act as an indicator of the total organic and inorganic compounds dissolved in the water. The water supply should be filtered to a prescribed range to reduce the chance of complications and unscheduled maintenance.

The prescribed water quality values below change per manufacturer.

Resistivity: 0.05MΩ * cm to 6MΩ * cm     
Conductivity: 20µS to 0.167µS
TDS: 10 ppm to 0.083 ppm

These three values are interchangeable and easily measured with a conductivity/TDS meter available from instrument suppliers and hardware stores. 

The mineral content in water varies greatly depending on your location. Depending on your water source, the actual content of the water may consist of impurities such as free chlorine, chlorides, calcium, magnesium, and iron. 

Identifying the Impurities

Impurities in your water supply can be filtered, but the type of filtration system required depends on the concentration and type of impurities. The best way to choose a water filtration system is to have the incoming water supply tested at a local lab.

Based on the lab results, select the appropriate filtration system. A standard ion-exchange cartridge filters most municipal water sources to be within the desired range. If the lab test results show high concentrations of sediment, chlorine, or organic matter, the additional use of sediment and charcoal filters may be needed.

Water Impurities and Their Effects

Operating within the established guidelines reduces the adverse effects of contaminants in the water or water that is too clean. Scale and sediment are unavoidable, but proper filtration and maintenance can prolong the life of the water system within your environmental test chamber. If you disregard proper filtration and maintenance you may see these issues:

  • Scale and sediment build-up
  • Heater failure
  • Corrosion
  • Organic matter build-up

Deionizer Cartridge Capacity

The rate a test chamber consumes water is dependant on the chamber workspace volume and the climate conditions in the workspace over time. AES offers an optional, basic, ion-exchange cartridge that covers most scenarios by filtering all types of mineral impurities.

The filtering capacity of the cartridge is rated to 1600 grains. The capacity, in gallons of water, is dependant on the TDS of the supply water, and can be calculated as follows:   

1600 grains TDS/17.12 ppm=Capacity in Gallons

The formula assumes consistent water quality over the life of the filter and is not applicable to test chambers with water recirculation systems. In most scenarios, recirculated water returns to the filter with the original water quality.

There are certain cases where specimens under test release chemicals into the workspace and mix into the recirculated water, creating high ion concentrations and altering the water quality.

By sending the recirculated water back through the filter, the impurities are removed, and the supply water is ready for reuse. Supply water with high levels of dissolved solids may deplete ion-exchange cartridges at faster rates.

Test your water, know what chemicals are being released, and adjust the filtration choice accordingly.

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