It’s not hard for every home to have water purification on hand ( lifestraw and other means) and to stockpile some medicines ( vitamins and antibiotics) while it’s still possible to obtain them which the govt is attempting to stop
Common bleach would work just fine.
You would need guns to protect your stockpile. Stockpiles are only temporary. Stockpiles only work until they are depleted or the mob kills you and takes your stockpile.