My father has been having trouble with the pump he uses to pump water into his cabin. He has had several pumps burn out on him over the past few years and he's at a loss as to why they don't last. I'm hoping someone can give us some ideas on what we might be doing wrong.

Here's the pump info:
Remco Aquajet 55AQUAJET-ARV
Link: http://www.remcoindustries.com/Corpo...?f=Aquajet.php

The system starts out at a 100 gallon water tank. The pipe feeds from the bottom of the tank into a 3/4" pipe, which runs about a foot and connects to the pump. From there it pumps into a 3/4" pipe which runs downhill(around 20% grade) for 20' to the cabin where it then makes a 90 and runs up about 5' and splits 3 ways. (Overall the tank is about the same level as the floor of the cabin.) One of the splits runs about 3' to the kitchen sink; the second runs 10' to the bathroom and feeds the toilet, sink, and shower; the third runs about 5' to a on-demand water heater, which then runs to the kitchen sink and the bathroom. The water pressure has always been fine.

Anyway, we are at a loss as to why we burn through these pumps so fast. My only guess is that the pipe feeding into the water pump needs to be bigger than the pipe exiting the pump. (I know that's the case with impeller style water pumps.) Any assistance with this issue would be appreciated.