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Basics to know about, how the pressure reducing valve works?

Written by Pieter Paul de Jongh
Sunday, 28 November 2010 17:18

Assuming that the pressure in the main water line is higher than the pressure downstream in the home:

a. High downstream pressure pushes the rubber Diaphragm up, pulling up the Yoke and Disc which are connected.

b. The Disc moves closer to the Seat pinching off the water from the high-pressure upstream supply.

c. The pinching creates friction, which reduces the downstream pressure.

d. The reduced downstream pressure allows the Diaphragm, Yoke and Disc to move down.

e. This reduces the friction lost through the seat, increasing the downstream pressure.

f. A balance is soon struck between processes a to c, and d to e, thus providing the appropriate pressure.

g. Adjusting the Screw down increases the downward force on the Diaphragm, Yoke and Disc. This makes it harder to squeeze off the water flow, thus lessening the friction. The lesser friction increases the downstream pressure.

h. Adjusting Screw up decreases the downward force on the diaphragm, yoke and disc. This makes it easier to squeeze off the flow, thus increasing friction and decreasing the downstream pressure.

Adjusting the Pressure Reducing Valve

a. Loosen the Lock Nut.

b. Adjust Pressure

    • For more pressure, turn the adjusting screw in (clockwise);

    • For less pressure, turn the adjusting screw out (counter-clockwise).

c. Retighten the Lock Nut.

Cleaning the Pressure Reducing Valve Strainer Screen

a. Turn water to the PRV off by turning off the main waterline leading to the PRV - this valve is usually located where the waterline enters the home. Leaving the water on during cleaning may cause flooding.

b. Ensure no one is using water during this procedure.

c. Have a bucket handy to catch the water in the household pipes, which drains back.

d. Unscrew the Strainer Plug which is a large cap screw on the upstream side.

e. Remove and clean the stainless steel Strainer Screen.

f. Reinstall Strainer Screen, and Strainer Plug.

g. Carefully turn water back on, and examine the system for leaks.

Note; If the main line water pressure is too low, there is no valve that can increase the pressure. Only a pump could do this.

Last Updated on Sunday, 28 November 2010 18:00

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