RP Backflow Testing Changes

Backflow devices with freeze bags

In the most recent (10th) edition of the Manual of Cross-Connection Control  by the USC Foundation for Cross-Connection Control and Hydraulic Research a few changes were made for field procedures for backflow testing. Today we are going to examine the changes that were made for testing a Reduced Pressure Principal Assembly, also know as an RP. Lets start out with Test Cock Flushing

OLD WAY

Open test cock No. 4, open and close test cock No. 1, open and close test cock No. 2, open and close test cock No. 3 and close test cock No. 4

NEW WAY

Open test cock 4, open test cock No. 3, open test cock No. 2, open test cock No. 1; then closetest cock No. 1, close test cock No. 2, close test cock, No. 3 and close test cock No. 4.

WHY CHANGE?

According to USC this is to ensure that there is flow through the assembly to minimize the possibility of discharging the relief valve, especially if under a backpressure condition.

Next change is the procedure for flushing the field test kit.

OLD WAY

Close high side bleed needle valve, close low side bleed needle valve, close No. 2 shutoff valve.

NEW WAY

Close No. 2 shutoff valve, close high side bleed needle valve, close low side bleed needle valve.

WHY CHANGE?

According to USC, this is to ensure that there is flow through the field test kit to minimize the possibility of discharging the relief valve.

The Final change has to do with your reading from the Number 1 check valve

OLD WAY

First check valve reading should be 3.0 psid greater than the relief valve opening point.

NEW WAY

First check valve reading must be above the relief valve opening point and ≥ 5.0 psid

WHY CHANGE?

According to USC, to provide a required minimum value for the first check valve.