This may be a no-brainer question, but so far I haven't figured it out. Since I winterized myself (compressed air method), I'd like to test everything out before our first trip. Problem is, I'm not...
I would go ahead and use water from your outside faucet. If the water system (pump, etc.) is working ok, then add bleach to disinfect the system. Drain that water and fill up with potable water at the campsite.