I may be wrong but isn't a priming pot (sometimes called a leaf trap) recommended for an external pump that is above water level? I have a Sequel pump (Sequence) and for above ground installations they say you must have a priming pot so that the pump doesn't run dry. I have one on my pump even though it's in a pump house below water level--got it for the extra measure of preventing stuff going through the pump like baby fishes, algae clumps etc. and I am very glad I have it. My check valve is on the output side of the pump because I have a gravity fed system. I also did use a swimming pool pump for a short while last year--real energy hogs! The priming pot and pump were all one unit.

If it's shutting off the main valve - that would be dangerous in winter climate for those w/hot water or steam heat -

If you're lucky, you may be able to tighten up the valve so that it will stop. But it WILL come back. My suggestion would be to replace those valves en-toto everywhere you have them in the house with 1/4-turn ball-valves. I'm no plumber, but ever since I started changing mine out, (30 years ago in several houses) I've never had a leak and never had one fail to work easily. They don't cost that much more. The labor will cost much more than the valves. However, assuming a competent workman, that will be the end of your problem. If you've got gate-valves on your main supply -- as MANY houses do -- I'd suggest replacing those also. Like your toilet-supply valves, those gates are notorious for not working when you need them to. Both of these items have been expensive lessons for me over the years. Whatever your plumber charges will be a whole lot less than I've shucked out for the damages I've had to repair. It's relatively easy work for a pro. Shouldn't take very long and won't be too bad money-wise.

Yes. -Turn off the water to the house. -Open some other valves to drain the lines (preferably one of them is at a lower elevation than the toilet) -Flush the toilet to empty the tank. -Disconnect the supply line between the toilet valve and the bottom of the tank. -Then get two adjustable wrenches. One goes at the base of the valve, and the second one goes on the pipe or fitting at the wall. Use the first wrench to loosen the valve, and the second wrench to keep the supply pipe from turning. (Expect some water to dribble out, so a few towels and a bucket will be useful) -Once the valve is off, put a couple of wraps of teflon tape on the supply pipe threads (going in a clockwise direction), and screw on the new valve and tighten it using the two wrenches. It would also be a good idea to put on a new, flexible supply line. I prefer the ones with a braided stainless steel jacket and threaded fittings. Make sure that the ends match the valve and the tank bottom connections (they are sold with several different size end connections). I usually buy one that is several inches longer than the distance between the two fittings: a little flex is good, and it allows for a valve that ends up pointing in a different direction than straight up when you've tightened it. After you've done this, shut all the valves you previously opened and turn on the water to the house again. Open the new valve if it is closed. You will have some hissing and noise, and there will be some spitting when various valves are opened as air works its way through the lines: this is normal. Check for leaks where you replaced the valve, and tighten any fittings if there is a drip. This may sound like a lot of work the first time, but you should be able to do it in 10 minutes the next time! Good luck.