Originally Posted by Keybler
I need a pump that will suck water out of a 5gallon jug and pull it 4 feet up to the pump? and then push the water up to 3 feet up.
Can you submerse the pump and run it at a 7 foot head? Alternatively, can you place the pump lower than the water level supplying it so the supply ends up siphoning into the pump?
I think the problem may be that you're trying to suck the water 4 feet up and then push it 3 more feet. Any pump I've ever seen that can do that has to be primed each time and is generally a larger pump. (To put it another way, you'll have to fill the pump volute and supply line with water.) The pumps we normally deal with in the hobby actually just push water out of themselves and the supply water rushes in from a siphon or because it is submersed. (In other words, they don't really suck, they blow. That's why you have to have water in a HOB
filter for it to start working once you plug it in.) If you don't prime, the impeller just churns the air around itself (sometimes called cavitation) without drawing a vacuum on the supply side. If you have the ability to prime each time (Maybe by actually starting a siphon from the container you're filling back down to the 5 gallon jug, and then powering up the pump), this isn't that big of a deal. However, I think you'll need to look for a pump that can still push a 7' head at the flow you need.
I work with large (by hobbyist standards anyway) pumps in the construction industry. I don't know if there is an aquarium hobbyist version of a diaphragm pump or "mud hog" (these don't use an impeller) that might work or not.