fine for years but a few years back it failed out of the blue. I bought the rebuild kit from west and replaced both of the rubber valves as well as the bellows. It was a simple job but the rubber valves had gotten hard over the years and taken a set with just enough space between so that it wouldn't suck. I don't think gravity isn't the issue because the rubber is so stiff, even when new. The kit isn't very expensive and if I went to the trouble to remove the pump I'd replace the guts just because.