I had from time to time have problems with water as the most of our water supply comes from a stream that is just diverted to supply our house, Pig drinkers etc.
I did however come up with a cheap solution which was to buy a couple of 1000 litre tanks the ones that come in the wire cages cost about £35 and now we take our water from them all the time as this keeps the water fresh as the last thing you want to do is use stagnant water.
I also bought a small pump that has a 1100 watt motor not serious fast at pumping but does the trick then I got an Inverter 1500 watt (you can get these in machine mart) which is joined to a large tractor which I got given as the farmer told me it was Fu**ed but when I brought it home and gave it a long slow charge was fine.
Now for the most important bit I got a very small battery charger that you can leave on all the time and will ONLY top up the battery when the charge goes down the type you use on caravans, Boats etc.
Now if my power goes out and I run out of water all I have to do is flick a switch and I can fill up my header tanks again.
It's only when you have no water coming out of your Tap that you truly appreciate what it is to just turn on and let it flow.
Kindest regards to all
Joe