How to size/select a pressure reducing valve
Factors which play the most important role in selecting a proper pressure reducing/regulating valve include:
- Line size - should match the valve size, i.e. 3/4" valve for 3/4" line, 1" for 1", etc. Connections are almost always female NPT threaded as this is the most common connection on plumbing systems.
- Maximum incoming pressure - these may vary by model, but must always be greater than the incoming water pressure. Typical ranges are 300-400 psi.
- Outlet pressure range - adjustable on most valves, usually within 25-75 psi. Must meet plumbing system operating pressure.
- Additional features - some models may incorporate a strainer to protect the valve seats from fouling or offer in-line service design which allows for repair/replacement of components without removing the entire valve.
Additional things to keep in mind:
1.
Do not confuse pressure reducing valves with pressure relief valves (PRV’s). While the abbreviation is coincidentally the same, these are entirely different both in structure and intended use.
2.
Pressure reducing valves (also called pressure regulators) listed in this category are not backflow preventers. To protect the incoming water supply from cross contamination caused by backflow, siphon or backpressure - a separate device is needed.
3.
The most common factory-default setting on these valves is 50 psi, which is the typical residential pressure for domestic water. If adjustment is needed, see instructions below.
4.
These valves are directional and must be installed with arrow matching the direction of flow.
5.
Adjusting the outlet pressure on the pressure reducing valve is easy - use adjustable wrench or pliers to loosen the locknut on the top of the valve and then turn the screw clockwise for more pressure or counter-clockwise to reduce it. Be sure to tighten the locknut after desired pressure is set.
6.
Some models of pressure regulators come with a built-in gauge (or tapping on the body for the same), while others do not. A pressure gauge (0-100 psi is most common) is highly recommended to monitor the outlet (downstream or house/building) side pressure.
7. Models such as Watts LF25AUB-Z3 have a built-in strainer. If a regulator does not have an integral strainer,
a fine-mesh y-strainer or similar (on the inlet/upstream side) is highly recommended to prevent fouling of delicate internal components and will extend the life of the unit.
Common installation practices:
All examples below assume a typical configuration: listed left to right (from supply side to the house/building) - a main water supply line (municipal or other), preferably with a pressure gauge (to show inlet pressure), followed by a water meter (with shut-off service valves on both sides - recommended, may be required by local code), followed by the backflow preventer, followed by the pressure regulator (one or more - see below for details):
1. Typical residential installation - a single pressure regulator is sufficient for most applications.
2. Very high inlet pressure situation - (2) pressure regulators are installed in series, one after the other, reducing pressure in stages. This also helps to eliminate noise & whistling.
3. High variation in demand - common for multi-unit residential properties. Here, (2) pressure regulators are installed in parallel, each accompanied by (2) isolation valves. Isolation valves here also allow to repair, clean or change the manlfunctioning unit without any service interruption.
