Hello Mahendra, thanks for your question regarding the MERV rating and water filters.

The short answer to your question: No, the MERV rating does not apply to water filters.

First, I’ll give you a quick overview of what the MERV rating is. Then, I’ll talk a bit about water filtration.

MERV: The ASHRAE Standard for Air Filters

MERV stands for “minimum efficiency reporting value”. Is its meaning still a mystery? Initially, it was for me, too.

This rating system was developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). ASHRAE devised MERV as a guide for determining the average percentage of particles captured by a filter, ranging in size from 3-10 microns (0.000003 – 0.00001 meters), given a typical air speed.

Standard MERV values are 1-16, with 16 being the filter that removes the highest percentage of particles.

Water Filtration Methods

Pollutants in water are more slippery than those in the airstream. They can have strong molecular bonds to the water molecules. The nature and strength of these bonds depends on the type of pollutant.

The reason there is not one unified water filtration rating system is because of the complex and varying nature of pollutants and diverse set of purification methodologies.

So, the type of filtration you need will depend on the predominant pollutants in your water supply. Here are a few of the common types of filtration techniques, and briefly, how they work:

• Granulated activated carbon (GAC): These filters utilize the powerful natural absorbent, carbon. The “activated” part means it has an electro-positive charge, which increases its absorption capability. These filters are commonly used and should be changed fairly often.

• Distillation: This technique uses heat to vaporize and separate pollutants. It is very effective at reducing dissolved minerals, but not necessarily recommended for drinking water. Due to its low mineral content, it absorbs the helpful minerals from your body (calcium, magnesium, etc.).

• Reverse Osmosis: This filter requires electricity. It pulls water through a tight membrane, stripping away minerals along with many pollutants, including radium. This type of filter also wastes anywhere from 3 to 10 gallons for every gallon filtered.

The type and degree of filtration you should choose will depend on the type of pollutants in your water system and your budget for maintenance.

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