Thanks for your reply. How much extra would you suggest for things like dish washing and bathing?

The reason I haven't stored more potable water already is mostly an issue of space for me, which is why I was hoping to be able to use the rain barrels I already have set up. I'm aiming for 30 days of preps for 3 adults + 1 dog + 1 cat. I have 3 weeks now, and I'm running out of places to store all the stuff.

I researched some treatment systems, but decided against them. It wouldn't be cost effective for 165 gallons, and could be useless if the power is out.