I already have: 1 PUR Scout camping filter with multiple spare filters 1 MSR miniworks camping filter with multiple spare filters The PUR & MSR filters both have four level of purification An intake hose filter; A 0.2 micron filter; a carbon filter; and a iodine matrix to kill viruses. If I remember correctly I once calculated that I have enough replacement PUR and MSR filters, and spare parts to purify about 8,000 gallons. . But that would be a LOT of pumping. . . . I also started stocking those 7 gallon blue Aqua-cubes from Walmart. I had planned on getting 21 of them (3 weeks worth of water), but they ain't cheap! With tax their about $10 each. So after getting ten of them I decided that I'd be better off with a good gravity water filter. Went to Moosejaw.com. They had them listed for $169.95. Added in the 15% discount code of MAXIMUS, opted for the free (but slower) shipping, and my total was $144.45. . . Or about the price of 15 blue water cubes. . . So now I have 5 gallons of bleach; 70 gallons of water in blue cubes; 40 gallons in the HW tank; 40 gallons in the camper (most of the year); 8,000 gallons via hand pump camping Purifiers (will kill viruses); and 20,000-39,000 gallons via the Gravidyn. So I finally feel like I have a reasonable handle on the water situation. . Thankfully I have two sources of water within 150 yard of the house. A running stream part of the year, and a large duck pond full year round. I still plan to add bleach to the water after running it through the Katadyn Gravidyn, just to make sure. In a month or two I'll go back to Moosejaw and order 3 more candles for the Katadyn. I still want to buy a CZ rifle. . But I needed a better water filter more than I needed another rifle.