Red Seal Plumbing Practice Exam

If you have a standing pressure of 7 inches w.c. and an operating pressure of 5.9 inches w.c., then

1. the gas line is properly sized

2. a leak is present in the system

3. the gas line is undersized

4. the regulator is faulty

The correct answer is: the gas line is undersized

This is the correct answer because a standing pressure of 7 inches w.c. means that enough gas is entering the system, but the operating pressure of 5.9 inches w.c. indicates that there is not enough pressure to power the gas appliances. This means the gas line is undersized and cannot deliver the necessary amount of gas, leading to low operating pressure. Option A is incorrect because if the gas line were properly sized, the operating pressure would be closer to or equal to the standing pressure. Option B is incorrect because a leak in the system would result in a decrease in standing pressure, not operating pressure. Option D is incorrect because a faulty regulator would likely result in a decrease in both standing and operating pressure, not just operating pressure.