With out a clean source of it, you're dead in a week, zombie bite or no. How are you going to carry it? you can have multiple items. if you pick an item that has other functions too, all the better.

I'll Start:

1. Nalgene bottles(4): these wide mouth bottles each hold a 32 oz. of liquid and are super tough. They also sell bottles with survival kits- jeffcee
2. Hydration bladder

Hydration bladder is probably best bet.They eliminate the sloshing sound of Canteens plus take up less space when empty plus the last I looked my walmart had about 30 for 5 bucks each.
-Emperor_of_the_Nerds










3. Containers
The US FEMA website has some of the best information about water storage and treatment.
FEMA water storage
FEMA water sanitation
Containers are one of the the best ways for storing large amounts of water. Those 30 gallon Rubbermaid storage tubs you have can be cleaned out and filled with water. Follow the directions on the FEMA site on how to prepare containers and treat water for long term storage.
The FEMA water storage page tells how to use two liter soda bottles (and tons more) to store water. If you grabbed 30 2 liter soda bottles from a store and filled them with water, that would last one person about 16 days according to 1 gallon per day.
-spraymachine