For my normal job I do millwrighting type stuff. Which means I deal with pumps a lot almost all centrifugal pumps. Most of them are water pumps and they are really big. This is more small scale, but will still use centrifugal pumps. So now that I have a little above ground water storage I want to be able to do stuff with it. One of the things that would seem quite use full is just being able to move the water around with something other than a bucket. The only pump you are really going to be able to find are centrifugal, so its best to find something easy to prime especially for fire fighting if you are going to have the pump or hose above the level of the water, then total suction lift rating this is important if you are going to have the pump above the water level and if can handle dirty water or not if you are going to pump water from a stream or pond. The 2 major categories of prime mover to power the pumps for fire fighting and general use are Electrical and liquid fuel. Obviously electrical wont work when the power goes out unless you have a generator or power inverter but the electrical pumps will be more reliable as long as they have power. So for an electric pump I think this will be a case of less is more, as in a smaller pump will allow you to power it from a small generator or a power inverter. For ease of use a submersible pump may be the way to go, just sink it, turn it on and it will be moving water. There are 12 and 24 volt submersible pumps out there but most look pretty cheaply made and to provide enough power to deliver a usable volume and pressure to spray water on something from at least a little bit of a distance you are going to need something that draws at least 25 amps of 12 volt power. Note: if you are going to use a power inverter for a 120v pump and have a cheap modified sine wave inverter your pump output my suffer by as much as 20% over using pure sine wave power. One thing that catches my eye as far as electrical pumps go are the 1hp "water sprinkler" pumps at lowes and the 1hp "irrigation" pumps at tractor supply and submersible pumps at both tractor supply and lowes. I am going to have to look closer at them and compare GPH or GPM total head and price and see if I can find any reviews. I should be able to power a 1hp pump with my samlex 2000w power inverter. For liquid fuel I think the best most cost effective thing to use will be a gasoline engine. I have a very old briggs and Stratton 5hp engine I would like to stick a pump on. Only problem is it doesn't like old gas, I left gas in it for a year and when I tried to start it the little engine would not stay running until I added some fresh gas. So if you are going to store the pump and not use it very often put the gas in a sealed pressurized container such as an MSR fuel bottle that stays with the engine. That way fresh fuel goes into the engine and it starts right up, plus the separate fuel bottle makes it easy to change out the gas when ever you would like, just dump the old gas into your car and refill with new gas. Gasoline sealed up in an MSR bottle stays fresh for a log time, one of my friends recently opened an MST bottle that had gas in it from 1994 to 1996 and it was still fresh smelling. Most of the gasoline engine powered pumps in a box appear to be trash pumps made for very high volume and low pressure such as you would want for pumping water out of a flooded basement or flooded job site. I think an "irrigation" or "water sprinkler" pump would be more appropriate should be lower volume and much higher pressure than a standard trash pump. A 200cc 5 to 6hp class motor should be tremendous over kill for this application. A smaller 150 to 160 cc 4 to 5hp motor should still be more than enough. Then you have to pick your discharge hose, I think I am just going to try a standard 3/4 inch heavy duty garden hose. I don't know if it will work but this is the most logical thing to try first. For the pump inlet I say go big. Try to stay at least the size of the inlet if the pump has a threaded inlet, if it has a precast hose barb inlet then just go with that size. If you have a submersible pump don't worry about the inlet, just keep it under water.