Another quick question about Daryl's press. Lately as the pumping get harder I can push through a pumps worth but then it will not suck more in. As it sucks more into the line on the downstroke it will push it right back out of the hose. I thought it was the flapper valve but it seems okay. It always works well to start with but then starts doing this as it gets harder to pump. Has anyone else experienced this? It's like the pump needs primed but it can not get enough suction to prime itself. Maybe it is because the cavities are clogged and not enough is being pushed out to draw enough in.