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" Plumbing pro Art Slegers creates an indoor dust storm as he cuts through old tile in a client&amp;#039;s Parsippany, N.J., shower. He&amp;#039;s wearing goggles, coveralls, gloves, a dust mask and\u2014no joke\u2014a shower cap. His 4-inch angle grinder reveals the guts of the shower supply, a system that remains a mystery to most homeowners despite daily use.  \u00ADUnderstanding what goes on back there can help a handy DIYer diagnose a leak, dispatch a vexing clog or\u2014as Slegers is doing\u2014upgrade from an old three-handle system to a modern single-handle valve, which can precisely control temperature without sudden drops in pressure. The replacement is tricky; this is not the time to learn how to sweat copper tubing. But even if you never plan to step into the stall wielding Channellocks and acetylene, it&amp;#039;s worth learning how the flow goes. Behind the Stall Walls  A Pressure-Balancing Valve Exposed A pressure-balancing valve like Moen&amp;#039;s 3570 Moentrol prevents a temperature swing in the shower when someone elsewhere in the house flushes a toilet or starts the dishwasher. This cutaway shows how internal valve mechanisms maintain consistent water pressure and temperature in turbulent conditions.   1 Check Stops Spring-driven gaskets at the valve inlets prevent high-pressure hot water from crossing the valve into a cold supply line or vice versa. (Hot water is at higher pressure in recirculation systems.) Screws in the stops shut off hot and cold lines at the shower for work on the valve cartridge. 2 Pressure-Balancing Spool Hot and cold streams slide a graphite-composite piston in response to fluctuating hot and cold water pressure. In 0.1 seconds, the piston (inside the chrome sleeve) seals or opens inlets to maintain balanced pressure between the two flows, which are still unmixed. Lab tests to monitor internal movement show the piston constantly vibrating back and forth. 3 Cartridge Pulling the shower handle slides the cartridge forward, opening two inlets to let hot and cold water enter and converge. Turning the handle opens one inlet as it closes the other, allowing users to adjust the temperature. 4 Temperature Limit Stop Screwed into the cartridge&amp;#039;s rod, this stop prevents a child from fully opening the valve to a scalding-hot setting. &amp;amp;gt; Shower Power &amp;amp;gt;&amp;amp;gt;&amp;amp;gt;  Make It Drain Grid Drain To get hair and scum clogs out of a grid drain, remove the grid screw. Clean the screw threads and mount bar using needle-nose pliers, a bent wire and old scissors. Pop-Up Drain Lift and tilt the stopper, and angled hinges slip free. Use pliers to clean the stopper and the spring within the drain. Lift-and-Turn Drain Remove the knurled knob from the stopper&amp;#039;s top and undo the screw beneath. Use pliers and scissors to get hair off the mount bar in the drain.  The Latest News on the Lowest Flows EPA WaterSense regulations require shower heads to use less than 2 gallons per minute (gpm) to douse a 5 x 3\u2013foot stall, while setting standards for pressure and coverage to ensure a satisfying shower, not a miserly trickle. Here&amp;#039;s how three manufacturers hit the new specifications. Moen \u2192 Water rides on spokes like a bike wheel&amp;#039;s to reach the perimeter of Moen&amp;#039;s 8-inch-diameter Envi shower head, avoiding the dry zones common in early low-flow models. Delta \u2192 A fat 0.26-mm droplet, twice the typical low-flow drop diameter, helps water in Delta&amp;#039;s H2Okinetic hold its temperature and feel like heavy rainfall. Kohler \u2192 Silicone polymers molded into distinct nozzle geometries let users set models like the Purist to deliver 1.75 gpm in a broad spray, a sharp beam or a wide deluge. "^^<http://www.w3.org/2001/XMLSchema#string>
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