now WHY would you need to store water? Do you live in a desert? Get a filter and be able to boil and treat the local water with iodine and chlorine bleach, and SAVE yourself all that wasted expense and storage space/hassle. YOur water heater holds 40 gallons or so, you know. remove the handle from the toilet, and that's 5 more gallons. If you dont, you'll flush it, out of habit! Dig an outside latrine, have some quicklime on hand. Watch out, you need to WD40 the drain valve threads on the water heater,and open it now and then, to clean out the crud. Most of them, the threads are corroded and can result in breaking off the valve, which means 40 gallons of water on your floor, if you are not prepared to plug up that pipe! :-) Ask me how I know that!
Both Mountain House and MRE's are EXTREMELY expensive, from normal sources, but thru a church, you can often get mre's for almost nothing. Hard winter wheat, salt, molasses, keep forever. Most other stuff is only good for 2 years, before it loses it's nutritional value. No point in storing it if all it does is fill you up. mere grass will do THAT. :-) There's cattails, dandelions, inner bark of pine, acorns, pine nuts, almost everywhere, altho you have to 'leech" the tannin out of the acorns and the turpentine out of the pine bark.