I've been using the Reliance 7 gallon Blue Aquatainer since 2001. I kind of designed my Wheel well Storage benches to store this tank, and it determined the height of the bed.
I made a Stem and put a Check valve on the end of it so that the lines do not drain themselves. It rests upright.
I used to use it with a Fynspray quality hand pump, but it wore out, then a cheaper Valterra hand pump which wore out very quickly.
Now I use a direct drive Jabsco 12v water pump that rests on the floor near the tank. I need to prime this pump, it does not get damaged when running dry as will most, but this pump does not have the gusto to prime itself.
These are the simplest electric water pumps available. it draws under 2 amps when running, so overall battery consumption is minute.
I got mine for about 70$ about 6 years ago but prices have risen significantly. I did not shop for the lowest price though for the following link.
http://www.ebay.com/itm/Jabsco-Elec...rg=20140602152332&rk=4&rkt=10&sd=260649968506
I use my 12v air compressor to to briefly pressurize the reliance Aquatainer to prime the pump. The pump instructions say to attach the pump to the bottom of the tank, but this is not feasible in my usage, and as long as I prime the lines and pump, it works fine just resting on the floor next to the pump.
It is not very loud, just a mild buzzing when it is on. Only one rate flow though, and battery charging voltages really increase the rate, and low battery voltage really slows it down.
This is much nicer to use than the hand pumps I had been using, and is cheaper than the Fynnspray/Whale pumps which in my opinion are the only quality hand pumps available, and these cost well over 100$.
I find the square cube makes the best use of space. Sure it is heavy, but it allows me to get RO water from vending machines easily. I only use this water for drinking or sometimes cooking and usually get 10 to 14 days from 7 gallons.
I dislike the store bought water jugs. I get Filtered RO water for 35 cents a gallon, buying a gallon jug or a 2.5 gallon jug comes out to 75 to 1.25 a gallon or possible much more, so you really pay for that disposable convenience.
I've looked into tanks which one can mount to the underside of the vehicle, but then to fill it with filtered water, one needs a transport medium, or a long quality hose and a means to keep it sterile, So I gave up on that and just use the transport medium as the tank.
Every so Often I pour boiling water into it and shake it up to sterilize it, but I've never noticed anything growing in the tank.
The Lines are a different matter, and I need to replace these.