How Whole House Water Purification Works & What It Removes

How Whole House Water Purification Works & What It Removes
by David Eastham

The idea behind whole house water purification is to place a filter system on the cold water supply as soon as possible after it enters your home. This way you will have contaminant-free water in your kitchen, the showers, all over, even for the dishwasher and for washing clothes. In this article we will discuss what needs to be removed from your water, how these systems clean it out and what system would be the best for you.

1. What should a good home water purifier do?

Simply put, any good whole house water purifier should give you clean, healthy water by removing virtually all (over 99%), of the debris and harmful contaminants from your water. This would include chlorine, THMs or the toxic byproducts of chlorine, SOCs or synthetic organic chemicals, lead, weed killers, insecticides, pesticides, pharmaceutical drugs, etc., the list goes on and on.

2. Okay, how in the world can these systems pull the contaminants out of the water?

Before we start I want you to know these are called systems because no single filter can do all the work. There are a series of filters in any system that do the work and they all begin with a pre-filter for removing the large particulate matter that could jam the filters that follow.

When it comes to removing the harmful chemicals compounds nothing is better at the job than activated charcoal. The Environmental Protection Agency has long recognized activated carbon as the best technology for removing the chemical bad guys, so, a carbon filter is likely to be next.

Stage three of the process is where things differ. This stage may be a distillation process, it might use reverse osmosis, or stages two and three could be combined together in a newer technology using ion exchange, called multi-stage or selective filtration.

Distillation is a process that passes water over a heated coil to form steam that rises to a cooling tank and condenses back into a liquid. This process kills any remaining bacteria in the water, and it removes inorganic compounds like lead, calcium, potassium, etc. (The process does not remove organic chemicals, so, a distiller must always be used in combination with a carbon filter).

Only three or four gallons a day is produced by these units so you can see they are very slow. Also, the electricity needed makes them have a relatively high energy cost.

Garage Storage Units

In the reverse osmosis process water is forced against a membrane screen about as thick as a piece of cellophane. The membrane is semi-permeable allowing only particles the size of a water molecule, or smaller, to pass through. This effectively screens out all minerals and even a large percentage of the water itself. Like distillation this process does a poor job on organic chemicals because their molecules are too small to be trapped. Consequently, a carbon filter must also be used with them.

These units are similar to distillation since they produce only a small quantity of filtered water per day and they waste two or three times what they produce. To create any volume of water they need a special storage tank and often require an added booster pump to create adequate pressure in the system. Cost of the equipments and subsequent operating costs and waste make these units similar to distillation systems in overall costs.

Both distillation and reverse osmosis systems remove all the minerals from the water, including the ones your body needs. When the minerals are removed, the water changes it acidity and will tend to re-balance itself by stealing needed minerals, like calcium, from the body. For this reason, many health experts consider this water unhealthy.

The third system starts with the adsorptive power of activated charcoal and it is blended with a chemically charged resin to create a very different, but highly effective, filter media.

This blend is compressed into a solid carbon block in which contaminants bond either chemically or physically, like little magnets, to the adsorptive surface. Minerals like lead or mercury are then removed by an ion exchange that chemically attaches them to the resin. Chlorine, herbicides and other chemicals physically attach to the charcoal through adsorption. This compressed carbon likewise includes a tiny, sub-micron pore structure that will remove any chlorine-resistant cysts like Cryptosporidium and Giardia.

Selective filtration is it not designed to handle salty water, but, since most of the nation does not suffer from that problem, it’s usually not a big issue.

For people without salt water issues, there are big pluses to these systems. They filter water rapidly with little resistance to the water flow, so there is no requirement for storage tanks or booster pumps which means lower initial costs and lower operating costs.

3. Which system will work best for you?

If you are dealing with salt water problems, you definitely want to go with a reverse osmosis system. Yeah, it is wasteful and expensive but, it will clean up the water, believe me.

If you don’t have the salt problem, you will be happy with the selective filtration process. They are very compact, less expensive to own and operate and, if they are installed properly, they work virtually maintenance free.

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