I have a waterfall for my pool which is very tall. The pump was installed at the top for some reason and must suck the water out of the pool (approximately 30 feet up). It takes a long time and I'm afraid the pump will burn out. I prefer not to install a bulky check valve at then end of the line since it is in my pool. I have 2 questions:
1) Are there any thin check valves I could install in the pool that really wouldn't be noticeable, or
2) If I install the check valve up by the pump, would that create an airtight seal that would keep the water in the line instead of running back into the pool? Simply keeping the water in the pump won't do, I need to keep in in the pull line as well. Would this work if I installed it at the top (like putting your thumb over a straw and pulling it out of your drink to keep the water in it?)

If you can't replumb this and put the pump at the other end of the line then put the check valve there. Get as close to the line as it comes out of the pool.