You can't usually raise the water level, there is an overflow tube that's part of the tank's mechanism which sets the water level.
It seems to me that some of the rubber flapper valves are supposed to float after being pulled up. That would make the flapper stay away from the seat till the water drains out. It may be that some others don't float, this is possibly a means of letting you do a minimal flush for small "deposites" by just holding the flush handle for a moment. You could attach a pingpong ball or some other floating object to the chain just above the flapper valve, that might help let it float. However you'd have to be sure the buoyancy wasn't enough to open the flapper whether or not you pull the chain. See if the flapper is hollow? that may be an indication whether it's supposed to float or not. Very possibly it's just the air that's supposed to be inside the flapper is not staying inside. Tom
