I take a 4 cup glass measuring cup, put filtered water in it, then microwave for 15 minutes. I notice that after 10 minutes it boils and to sterilize you need 5 minutes of boiling. Then I use sterile water to rinse the bottle. Next I fill the bottle back up add some vinegar and let it sit for a half hour.
When I used the Grossan machine, I ran vinegar and sterile water through it, then let it sit.
But if there is no time to let boiled water cool, I could see why you refrigerate. I don't know whether the water stays sterile when you put it in a jar (the lids never look clean to me) and put it into the fridge.
The other question I have for those of you who use sterile water from the pharmacy. You need a lot of water to do the NeilMed or Grossan Nasal rinse. How large do the sterile water bottles come in? It seems like you would be storing a lot of water.
By the way, I used to do the tap water thing too. But after a series of infections, I changed all my habits. And one of them was to change to using sterile water and the nasal rinse saline packets, rather than making up my own solution.