[JRTJH]

If you'd drink from that garden hose, it's safe enough to use to sanitize your trailer water system. If you'd refuse to drink from it, then don't use it to sanitize your trailer.

The objective is to fill the lines with "potable" water, introduce chlorine to disinfect the plumbing so it doesn't present a hazard if the water is used in cooking, brushing teeth, etc.

In other words, if the water from that hose is "safe enough to drink" then it's "safe enough to sanitize your trailer.