100 gallons = 800 lbs.
250 gallons = 2000 lbs. That's 1-Ton of water.
For the long term, what you could save in fuel mileage with the smaller tank you could add your own purification system in the van and keep the smaller tank. Then simply find places to re-fill the smaller tank while you're out. Even if you had to give someone a small fee for the water it beats the heck out of paying $3.50-$5.00 gallon for gas. Gas prices are only going to keep going up that I can see. If gas does go to $5 a gallon you'll wish you'd have stayed with the smaller thank.
Considering I am just getting started with a full size van set up, I was leaning toward a 275 gallon pallet mounted tank as they sell new for $150 on Craigslist from a local supplier. Without question I too am a bit concerned for both the gas mileage and the dangers of being "Malachi Crunched" against the dashbord... as neither are very inviting risks.
Ironically, I had planned to buy the 275 gallon tank this Saturday in hope to have my tank layout, pump, and plumbing in by Monday. It's kinda hard to start setting things up without it, so today was rather unproductive.
As fate would have it, I happened to park next to another mobile van at a Walgreen's today, and started asking a bit about his experience, set up, etc. This guy was so cool, that he explained to me he had just 'downsized' to a 100 gallon tank, and switched his rig from running a gas generator to a 2000 watt power inverter that he paid less than $200 bucks for. Meanwhile I had just scored a brand new 'in the box' gas generator yesterday on Craigslist for about 25% it's retail value. :xyxthumbs:
Anyway, by the time we were done he said; "Hey since you're just getting started if you haven't bought a tank yet, I have a 250 gallon tank, and it's like new, you can have it."
- I offered to pay him something for it, and he basically said; "No man, call me before 10am meet me here tomorrow morning and it's yours." -From what he explained it's rectangle, low profile and has two molded grooves for the strapping, which is exactly what I wanted, but couldn't afford. Definitely made my day!!!
The best part being I really didn't like the 'pallet style' tank as the design seemed a bit dangerous, and this just saved me a $150. People in this business seem a lot less 'threatening' than most of the businesses I've been in prior... that's for sure. Definitely found a bunch of help here already!
Looks like I'll be hunting down some metal fabrication shops tomorrow and seeing if I can score some stainless steel straps to anchor it in. The van I bought already has a cage installed to protect the driver from the load, but I highly doubt that will stop a 2000# water tank... so I am planning on anchoring it to the cross member frame with some heavy duty stainless steel nuts, bolts, and locking washers. Ought to be a lot of fun drilling through the sub-frame
It seems the closer I get to having all the 'essentials' together to get started, the less I have been sleeping! -I can't wait to get this rig rolling.
PS - For the record, I probably won't fill the tank up more than 150 gallons unless the demand requires it, but I figure since I have the room the 250 gallon will be great... especially if things go well in the morning.