WaterSense endorsed shower nozzles on the market use one of two accepted mechanisms to scale down water flow. Some shower nozzles inject air into the flow thereby maintaining steady water pressure in the face of decreased water flow. The extra air may reduce the temperature slightly.
Non-aerated heads maintain pressure by making water flow through smaller openings. This mechanism gives the water a pulsating quality, which causes the user to feel like he is having a gentle massage.
You can perform a simple test at your house to discover if your present nozzle is EPA compliant. Put a two quart jug directly under your nozzle so that all the water flows into the container, and turn on the water at a temperature you like for your showers. If the 2 quart container fills in less than 12 seconds, then your current head is permitting water flow at more than 2.5 GPM and is therefore not EPA compliant. Before starting the test, you might conserve time by looking to see if your shower nozzle bears the WaterSense label. Your shower nozzle might have a sticker reading 2.5 GPM or less . This means it conforms to government requirements for water efficiency, but is not as strict as shower heads displaying the WaterSense label.
You can find water saving heads at your local retail outlet (Home Depot, Loews, etc.). With a family of three of more you can expect to save $200 a year or more.
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Resources; 1st Choice Plumbing Inc.; 3502 Taney Road; Baltimore 21215. are experienced in the selection and installation of low flow water heads. Call (410) 967-6547