Blog Post

Pure Water

Our family decided that we wanted to have purified water to drink and cook with in our house. I am not saying that the water from the tap is bad; it's just that we wanted certain things filtered out of the water that is put in by the water department.

The latest Minneapolis Water Works report is filled with fun facts. You can download it from the city of Minneapolis's website. The quality of the water being produced is really high, but there are things in the water supply that I want removed before I drink it.

Most Reverse Osmosis systems (RO) have several filters and a holding tank that you mount under the kitchen sink, with a spigot that is mounted at counter level. There are usually 2 or 3 filters besides the RO filter itself. The water first passes through a sediment filter, which removes dirt and sediment, then the water passes through a carbon filter, which removes the chlorine. After that, the water goes to the Reverse Osmosis Filter, which filters out most of everything else. The pure water then goes into a holding tank, while the waste water (brine water) goes into the drain. The reason for this waste is because there needs to be a higher pressure on one side of the RO membrane. Most of the systems generate about 10 gallons of waste water per 1 gallon of pure water.

One point to note is that the “waste water” really shouldn’t be called waste. This “waste water” is tap water that has been filtered by the 2 or 3 pre-filters. It is probably cleaner than the tap water.

There are several different models of RO systems to choose from, and the standard systems usually range from about $100 to about $300. Filters are very inexpensive for this type of system, with typical filters costing about $30 per year, not including the RO filter itself. The RO filter should be replace every 2-5 years, depending on usage, at a cost of about $75.

There are two types of special systems that generate less waste water. One specific RO system from GE, called the Merlin, has a lower waste rate, as well as having no tank to deal with. It wastes 3 gallons per 1 gallon of filtered water. This system is about $400. Annual filters are about $40 per year, not including the RO filter. The RO filters should be changed approximately every 3 years, at a cost of about $190.

The other type of special system is called the “Zero Waste” RO system. This system takes the waste water and puts it back into the household water supply line, usually the hot water line. By doing so, the waste water is not disposed and is re-used. The process is like this: the cold water is drawn into the system, where it is filtered by 2 or 3 pre-filters. The water continues on to the RO filter, where the pure water goes to the holding tank. The waste water side of the RO filter goes to a high pressure pump, which pumps the water into the hot water line under the sink. So for each 1 gallon of pure water produced, 10 gallons cycle through the system. These systems cost about $300-400, and the filter costs are about the same as a non-zero waste system, i.e. $30 per year, and $75 for the RO filter every 2-5 years.

We purchased the Zero Waste Reverse Osmosis system from Costco (one of my favorite stores). After using it for 9 months, we’re pleased with it. There are drawbacks to the Zero Waste RO system, though. The first one is that you have to have power available under your sink for the pump. Once that is taken care of , the second drawback is that the cold waste water is being pumped into the hot water line. After a minute or two, the cold water line is now drawing warm or hot water, while the hot water line is drawing cold water. This situation rights itself in a few seconds, just as if you were waiting for the hot water to reach the farthest faucet in your house.

The bottom line is, we wanted to remove certain things that Minneapolis is putting into the water, more specifically fluoride. Since this is present in our tap water, and most bottled water is tap water, by removing fluoride, among other things, we are now drinking water that is cleaner.

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