Parallel pumps
I've got both the manual and electric pumps on my 27, but they're connected in a parallel setup: the electric pump is connected to the (only) hose, which is led to a Y valve in the stern locker. Normally, the y valve allows the electric pump to discharge overboard. If the electric pump fails, operating the y valve allows the manual pump to draw water through the electric pump's intake strainer, and pump it through a "T" fitting just inside the through-hull. (One through-hull serves both the electric and manual pumps.) The advantage to this over the series connection is that my electric pump doesn't have to pump through the manual pump--the discharge is routed overboard, bypassing the manual pump. The downside to this setup is that only one pump is useful at a time. (The manual pump serves purely as a back up to the electric pump.) From a practical standpoint, that's how I use the system anyway. I've investigated adding a second intake hose dedicated to the manual pump, so both pumps could be used at the same time, but there is so little room to run the hose in the bilge that I haven't done it yet.Randy