NEWSplash!: UV Purifiers – What They Do & What They Don’t Do

UV Purifiers: What They Do and What They Don’t Do
By Richard C. Stump II

UV is short for ultraviolet. Ultraviolet refers to the wavelength of light generated by the lamp inside the purifier. UV purifiers are becoming increasingly common in homes that have private wells. If we examine the device from the outside and work toward the inside, we find it consists of a chamber usually made of stainless steel or, in some cases, of plastic lined with stainless steel. The chamber on home units is usually about four inches around and, depending on the model, from twelve to twenty-four inches long.

Inside the UV chamber is a clear sleeve that allows UV light to pass through it. Normal glass blocks most of the UV light, so quartz materials are often employed. The heart of a UV purifier, a germicidal ultraviolet lamp, is in the center.

A germicidal lamp works on the same principle as a fluorescent lighting tube. A fluorescent lighting tube contains mercury vapors that are excited by electrical current. Light is produced by the UV light’s striking the tube’s inner fluorescent phosphorous coating; however, the phosphorous coated glass keeps most of the UV light inside the tube. A germicidal lamp, on the other hand, is made of a quartz material that allows the UV light to pass through the tube and into the surrounding area.

Water from the home flows past the area exposed to UV light. The UV light damages the internal structure of the bacteria and renders them harmless. The UV light generated by a germicidal UV tube is so intense that it can cause burns in a matter of seconds. That’s why the UV tube is enclosed inside a metal cabinet.

Since UV light is blocked by solid material just the same as visible light is, the water needs to be free from suspended particles and substances, such as iron, which cause stains. Even with clear, iron-free water, the UV chamber must be cleaned at least once a year. UV lamps seldom burn out, but they slowly lose their efficiency with use, so that after one year their efficiency becomes too low to be effective. Therefore, the bulbs need to be changed yearly.

Every UV purifier has a maximum flow rate that if exceeded will allow bacteria to pass through the system, so be careful to choose a UV that is adequate for the home in which it’s being installed.