Plast

2-Port vs. 3-Port Relief Valves. (Image source: Plast-O-Matic Valves, Inc.)

3-port designs, on the other hand, are generally limited to #1 and #2.

2-port relief valves require a piping tee for by-pass and relief applications, but not for backpressure or anti-siphon applications. Unlike three-port style valves which are placed directly in-line and cause a drop in both pressure and flow, a valve "teed" off the line usually offers the best system design and ease of maintenance.

In most relief and by-pass applications, 3-port valves do not perform as well as 2-port valves installed on a tee. No 3-port relief valve is suitable for use as a backpressure regulator or anti-siphon valve, and no 3-port relief valve will deliver the flow and performance of a Plast-O-Matic 2-port relief valve.

The illustration above shows the essential differences between 2-port and 3-port relief valves; note the advantage of piping convenience in the 3-port installation compared to the advantage of unhindered flow in the main pipeline shown in the 2-port installation.

Advantages of a 2-Port Design:

Advantages of a 3-Port Design:

Plast-O-Matic offers the highest capacity backpressure/relief valve for both applications; Series RVDT 2-way and Series TRVDT 3-way. Because of the advantages of the 2-way valve, most sizes in PVC are available off-the-shelf. The TRVDT is available on special order. In addition to these high performance models, they offer economical options in our Basiks price/performance line.

Source: Plast-O-Matic Valves, Inc.