What is the minimum gap required between the pipe from the softener and the drain for discharging backwash?

The minimum gap required between the pipe from the softener and the drain for discharging backwash is 1-1/2 inches. This gap is crucial for preventing any potential cross-contamination of the potable water supply with wastewater.

In a backwash process, the water flow is meant to cleanse the resin within the softener, and the wastewater created must not enter the drinking water system. By maintaining a gap of 1-1/2 inches, it helps ensure that there is an adequate air gap that can prevent backflow, which is a critical aspect of plumbing codes and health safety regulations.

Choosing a gap that is too small might not provide sufficient protection against siphoning, potentially allowing wastewater to contaminate the clean water supply. Hence, the requirement of 1-1/2 inches is both a practical and a code-related stipulation to protect public health.