Adding a Second Bilge Pump
by Tom Soko
After reading an article in one of the glossy sailing magazines a few years ago, I decided that I wanted to follow the author's advice and add a second, smaller bilge pump to Julandra. I wanted to minimize the amount of "backwash" that flowed back into the bilge after the pump turned off, and I wanted a smaller pump that would take care of the nuisance amounts of water in the bilge. Further research told me that I did not want to install a check valve, and I did not want to combine the smaller and larger bilge pump in any way. I wanted two independent systems. Soon after I bought Julandra I had replaced the stock bilge pump with a larger more dependable unit, a Jabsco 1750 GPH, and installed a new float switch in the middle compartment of the bilge. I had also replaced the corrugated plastic hose with heavier-duty, smooth-bore hose back to the transom. It worked well, and quickly drained the bilge, but the amount of backwash was substantial. I purchased a small 500 GPH pump with a ¾” discharge port. If I could have found one with a ½” discharge port, I would have bought that. I moved the larger pump to the middle compartment of the bilge, and mounted the smaller pump in the aft compartment, which is the lowest part of the bilge.
I knew that putting the float switch in the same compartment would cause the pump to cycle on and off, so I mounted the float switch for the smaller pump in the middle compartment, and the float switch for the larger pump in the forward compartment. Not wanting the larger pump to come on unless the water level was high, I mounted its float switch on a small piece of ¾” StarBoard. Each pump is independently fused and wired directly to the house bank, and each one has its own three-way switch at the nav station. I also purchased two small 12V alarms at Radio Shack, and wired them to sound when a bilge pump is on. Each alarm has a different pitch, so I can tell which pump is running, even from the cockpit.
The magazine article suggested either a short hose length to the midship rail, or a vented loop mounted above the water line. I chose the vented loop, and located it next to the galley sink, up as high as it would fit. This centerline location, near the bilge, allows only a very small amount of backwash when the pump turns off (about a cup?). I ran ¾” hose up to the vented loop, and then right after the vented loop I reduced the size of the hose down to ½”.
The ½” hose runs under the engine pan, then aft to the transom, to its own dedicated ½” marelon thru hull.
I have heard that other owners have reduced the size of the hose right at the pump down to 5/8”, and then ran 5/8” hose up to the vented loop and back to the transom. Even at hull speed, when all thru hulls at the transom are under water, the vented loop is well above the water line, and water cannot siphon back into the bilge. My bilge is now much drier, and the redundancy of two bilge pumps is comforting.
Tom Sokoloski
Julandra #659
Noank, CT