Dual Bilge Pumps

This project came about because of a glaring item on the surveyor’s report: “Vessel has only one manual bilge pump installed, no backup pumps, manual or electric, are present”. Just to put some number with the problem, considerer this: Hollander and Mertes, in their book “The Yachtsman’s Emergency Handbook” quotes the following approximate flow rates:

• Three-finger sized hole near the waterline:            4762 gal./hr.
• Three-finger sized hole 3 feet below waterline:        7937 gal./hr.
  

That prompted some research into electric bilge pumps on my part.  

Most boats have the bilge pumps permanently mounted. Some pumps are automatic and others rely on a separate switch. The automatic pumps come on periodically and sense the presence of water by the amount of drag on the motor. I don’t like battery-drainers so I avoided the automatic pumps.  

Another problem is that pumps often clog with bilge debris at a critical time. That gum wrapper, old paper napkin or other piece of trash doesn’t seem important until it clogs your bilge pump or jams your float switch at the wrong moment. Therefore, any solution will have to allow for easy access to the pumps and switches. Luckily, I have a 14-inch by 17-inch access hatch in the cabin sole directly over the deepest part of the bilge.  

Another annoyance is that the bilge pump is down in the bilge and the hose runs up from there to just under the deck and then down to the outlet. The loop is there to prevent back-siphoning water into the bilge. Ideally, it should have a vent at the top of the loop as a siphon-breaker. The problem is that when the pump shuts off, all the water left in the hose runs back downhill and back into the bilge.  

After mulling all this over, I came up with my solution. I used two bilge pumps. The smallest one will be mounted as far down in the bilge as possible. It would handle the small, day-to-day leaks; stuffing box, rainwater, splashes down the companionway and similar small amounts of water. The 360 gallon per hour pump has a 3/4” outlet but I reduced that down to accept a 5/8” hose. The idea was to leave as little water in the hose as possible. I found a fitting for a water pump that I could use as a quick disconnect fitting for the 5/8” hose. I could have placed a check valve in the hose to keep the water from draining back into the bilge, but check valves are also prone to clogging and failing so I chose not to.  

The placement of this pump was a little tricky. It had to be low enough to get the maximum amount of water out of the bilge but placed too low, the water draining back down the hose would restart the bilge pump, resulting in perpetual pump cycling until the battery ran down. 

The real bilge pump is mounted higher, with its own bilge pump switch. The theory is that the small pump will handle the small day-to-day leaks while the big pump is there to handle the serious leaks. This pump outlet is not reduced in size.   The bilge pump hoses are the more expensive, heavy-duty hoses with the external spiral reinforcement. This hose costs more than the common corrugated bilge pump hose, but the smooth walls allow much more water to be pumped through the same size hose.  

Both pumps and their associated switches are mounted on a piece of Starboard (R) polymer sheet. The bottom is contoured to fit the sides of the bilge and generous limber holes are provided.  The pump mounting board should not act like a dam.  

A small 2-inch by 3-inch piece of Starboard (R) is screwed to the bottom of the board to hold the switch for the lower pump. The upper pump is mounted on a 4-inch by 4-inch square of Starboard (R). This pump is heavy, so a triangular brace is fastened under to help support the pump. All the pieces are screwed together using stainless steel self-tapping screws.  

A handle is cut out in the top edge of the board. The board slides up and down on wooden rails. Those rails are screwed to the under side of the deck at the top end and bonded to the sides of the bilge at the bottom end. I made the rails from teak left over from another project. Other woods will work fine if epoxy coated to resist water.  

All the pump and switch wires are left as long as possible and led up to the upper part of the mounting board. This is to keep any connections out of bilge water. I used a flat trailer connector to make the connections to the boat’s electrical system. This allowed me to easily disconnect the pump board when I need to clean or service the pumps.  

The wires are also encased in plastic spiral wrap for protection. The wire bundles are fastened to the board with nylon cable clamps to provide strain relief. The connections themselves are made with heat shrink butt connectors that are then covered with additional adhesive lined heat shrink tubing. Nothing like a good belt and suspenders approach where electrical connections are involved. 

Both pumps are wired directly to the batteries, bypassing the normal battery selector switch. Fuses are installed near the batteries to provide over-current protection for the pumps.  

With the wooden rails in place, the pump mounting board can be slide into place and the hoses connected. Each hose travels under the engine and then to a loop of hose that rises well above the water line before exiting the boat. There is enough slack in the hoses that the board can be pulled up far enough to service the pumps and clean the strainers on the bottom of the pumps.  

The pump system takes only about three days to put together. The installation, plumbing and wiring aboard the boat takes a lot longer than that, mainly because of the cramped working space. The total cost of the project is around $250. Not cheap, but consider my alternative – no pumps.  

What will I do differently? Well, a couple of things. I used a stock plastic mounting bracket for the lower pump. It seems a little flimsy and I might replace it with a stronger one made of Starboard (R). I will have liked to have both pump switches on the same side so I can lay the mounting board down flat, but the bilge is too narrow for that. The upper pump can be bigger and mounted lower. I will also like to find a quick disconnect fitting for the large pump’s hose.  

None of these problems is serious enough to redo the system, but consider these suggestions if you decide to build a similar system.      

                    

Comments

[Paul Esterle]

While Im sure there are other, equally good, brands of bilge pumps out there, Ive had consistently good life from my Rule pumps. Good selection of sizes and reasonable prices. Do you prefer a different brand?

Paul Esterle
Freelance Boating Writer
Captn Pauleys Place
The Virtual Boatyard
www.thevirtualboatyard.com

[Sean Long]

Very cool! I see that you selected the tried and true Rule pumps for the project, any particular reason why you picked this brand?