You'd be seriously degrading the performance of the electrical pump (if it worked at all), and you'll really have no redundancy in your systems. A clog of any kind anywhere would incapacitate both pumps.
You'll be far better off with two separate systems, including discharges.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)