A dry bilge for $50

Ben Stein

Ben Stein

Publisher of Panbo.com, passionate marine electronics enthusiast, completed the Great Loop in 2017.

10 Responses

  1. Gary H Hagstrom says:


    Where did you route the discharge? It seems to me that is always a key issue for these systems. I hate to install more through hulls and combining discharges is also frowned upon.

    I would like to solve this issue on Crackerjack since it lies bow low so you have to lay over the engines to mop each hull dry.

    All the best

    • Ben Stein Ben Stein says:

      I was able to route into a deck drain elbow. It discharges well above the waterline already had a couple of drains meeting so I didn’t feel this was an unreasonable risk to take. I suppose it’s possible that if the discharge of the drain were sufficiently backed up it might drain towards the bilge but I’m not sure the pump would allow the water through and even if it did the main bilge pump would be able to evacuate the water. Plus if those drains backed up they’d overflow into the bilge as well so it’s effectively the same risk.

      -Ben S.

    • Colin A says:

      I would pump it into a cockpit near a cockpit drain myself, but that might annoy some people (stains etc). I have run similar ones into outboard motor wells before (thou those are less and less common). On some larger power yachts I have worked on I have seen the Arid bilge tied into sink drains well above the water line several times. A siphoin break above the sink would prevent most issues in that setup.

  2. Matt Byrne says:

    Since MIBS, I have been slowly working on this project too after seeing a COTS system that is sold by the pump manufacturer on Amazon for a very reasonable, though not $50 (!), price. Thanks for the thoughts on drain spots. That has been slowing me down. I am thinking about building another for my shower sump , which always has nasty water in it. Where did you find the filter? I am going with a timer (per article) but you now have me wondering about Rhasperry Pi for intelligence. I am never going to complete my boat to-do list.

  3. Scott Booker Scott Booker says:

    Same principle as the Rule 25SA 500GPH bilge pump that I have been using in my PWC’s for years. For me they have worked well, but they are susceptible to getting “crudded up”, which flummoxes the current-sensing. I’ll be interested to see how the long term reliability works out for you.

    Well done!

    • Ben Ellison Ben Ellison says:

      Looks like a nifty little pump…


      … but I don’t see how it could attain the same level of “dryness” as what Ben S put together.

    • Ben Stein Ben Stein says:

      You probably noticed the strainer style filter on the pump inlet; without that filter the pump tends to get jammed with debris. With that filter in place it’s been running for over a month without any issues.

      As for the current sensing side of the house I’m only about six weeks into running it but I’m very happy with how it’s working. Most nights it runs for exactly one minute. If I’ve done something in the engine room to spill a little water it might run slightly longer. I think I’m going to add a step to send me a summary email after the pumping session is over. That way I can know how long it ran and the current consumption over that time period.

      -Ben S.

  4. Scott Booker Scott Booker says:

    This article got me thinking… as I have a perpetually wet bilge(s) in the Christina B, primarily due to condensation from my chilled water air handlers.

    As I mentioned in a comment above, the control circuitry and monitoring that Ben put together reminded me of what is built into the Rule 25SA. So I decided to do an experiment.

    I bought a new 25SA and did some current monitoring so I could roughly figure out where they have the current threshold settings for running the pump. Then I tore the little sucker apart to expose the motor and control board.

    Then I bought the same diaphragm pump that Ben and the other author used. I did some quick instrumentation.. and noted that my numbers agreed with Ben’s.

    Then I just hooked the diaphragm pump in direct parallel with the motor for the Rule pump. Based on my calculations, depending on the margins and how Rule did their code, this *might* work without further modification to the board.

    To my joy (OK… perhaps surprise) it worked right out of the box. The pump turns on, and if there is water to be pumped it will run until the pump runs dry (there is enough delay in the system to allow the pump to prime with a 3′ inlet hose). If the pump is already dry, the pump will shut off after about 10 seconds. Then the auto-timer will cycle every 2.5 minutes… checking for water presence.

    So this basically ends up performing like Ben’s rig (which I really like), but you don’t have to have the peripheral equipment that he already had installed on his boat. You don’t need to do any current sensing or write any code.

    I’ll continue to mess with it to make sure that it performs as expected under variable conditions. If need be I can remove the Rule motor completely and/or modify the current-sensing resistor that is installed on the Rule board. My knee-jerk is to remove the Rule motor, but I’m trying to keep the modification as simple as possible.

    If it all continues to work well here on the bench, I’ll 3D print up a nice enclosure for the motor/board and install it on one of my bilges the next time I run down to the boat.

    • Scott Booker Scott Booker says:

      If my calculations are correct…. I could actually leave the entire centrifugal pump portion of the rule in place and actually use both pumps (Rule and diaphragm). The Rule 500GPH could do the “heavy lifting” if the bilge has a lot of water in it (it will pump down to about 1/2″…. way below what my big pump will do) and then let the diaphragm pump do the finish work. All off of the same circuit.

      I’d still leave the Rule 3700 and float switch in place to do the “really heavy lifting”.

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