Residential UV–What Goes Where
Planning and Installing Residential UV Units
The Viqua manufacturer’s illustration above shows an ideal UV installation with pretreatment, individual optional by-pass assemblies for the all components, and the UV unit itself. It also shows an optional solenoid and temperature management valve, which would not be needed for most residential installations. Most residential UV installations are not this elaborate, and they don’t need to be.
UV is normally installed as the final item in a treatment system. Pretreatment needed depends entirely on the quality of the water.
UV always needs at least one pretreatment item, a 5-micron or tighter sediment filter somewhere in front of the UV unit to assure that there are no particles in the water to shade pathogens from the germicidal light.
Additional pretreatment depends on the quality of the water. Water to be treated should have less than seven grains per gallon hardness, less than 0.3 ppm iron and less than .05 ppm manganese. The carbon filter shown in the diagram is optional and might be included to improve taste, remove extraneous chemicals, remove a small amount of odor, or even to remove chlorine or chloramine if city water is being treated. (Disinfectants like chlorine are not removed to protect the UV unit, but to improve the quality of the water entering the home.) Carbon will not address iron, manganese, and hardness. The softener in the picture will treat hardness and small amounts of iron and manganese. If iron and manganese are excessive, separate treatment will be needed.
The UV Itself
UV units are sized mainly by gallons per minute treatment capacity. Typical “whole house” residential sizes are 10 to 18 gpm. The UV unit pictured above is a free-standing unit, but systems are also sold that have the sediment and/or carbon stage(s) built on the same frames as the UV chamber. See picture below. Most residential UV units are 115V systems that plug directly into a wall outlet.
The Viqua 12 gpm unit above has sediment filter and lead-removal carbon block built onto the same frame as the UV chamber.