Build Your Own DIY Arid Bilge or Dry Bilge System

Manual and automatic bilge pumps, whether submersible centrifugal pumps or remotely mounted diaphragm pumps, cannot completely clear a bilge of water.  Typically 1-3″ of water remains.  In a shallow bilge boat like the Catalina 25 used for this prototype system, this can lead to a substantial volume of water remaining in the bilge.  Water in the bilge can cause serious problems on many boats, including causing wood stringers to rot and internal fiberglass blistering.  Bilge water is also the primary source of that distinctive “boat smell”.

At the time of writing, there are two commercially available products that address this problem, with advantages and disadvantages compared to this DIY system.  The Arid Bilge system is a smart, but relatively expensive system.  The more recently introduced Dry Bilge system is smart, but less so than the Arid Bilge, and is much less expensive.  The Dry Bilge system appears to leave more water in the bilge than the Arid Bilge system, and appears less robustly constructed than the Arid Bilge system.

Both of these commercially available systems are intelligent, only operating their pumps when water is detected in the bilge, which results in less power consumption.  As a less intelligent and much less expensive alternative, this DIY system runs on a programmable timer, which draws power on a schedule regardless of whether or not water remains in the bilge.  Both of the commercial systems appear to not remove the last remnants of moisture from a bilge because they do not use sponges, and appear subject to clogging at their water pickup points.  This DIY system can remove the last remnants of moisture from a bilge, does not tend to clog, and costs less than $100.

This DIY system starts with common household sponges, which absorb moisture in the bilge areas.  The moisture in the sponges is sucked through small feeder tubing, leading to a simple suction manifold, with the suction generated by an inexpensive DC-electric diaphragm pump.  The discharge from this pump can be plumbed into the manual bilge pump outlet hose near where it drains to the through-hull at the transom (Plumbing to the hose near the through-hull at the transom may be considered important for safety.), or routed to the lifting cable through-hull on swing-keel boats.  The pump is controlled by an inexpensive DC-electric programmable timer, which can be installed on the electrical panel bulkhead.  For the prototype installation, the timer was programmed to engage the pump for two minutes every six hours, which resulted in a completely dry bilge in all seasons and weather, regardless of leaks and sailing conditions. In this case, the programming could be changed to pump less, such as for two minutes every twelve hours or one minute every six hours.

In many boats, there are separate bilge areas in which water typically collects.  For the prototype system, there is a separate pickup in each of these areas,  a total of three pickups for the system.  There is one pickup beneath the forward v-berth, accessible through the wooden hatch beneath the v-berth; one beneath the starboard salon floor, accessible through the small wooden bilge access panel; and one beneath the port salon floor, accessible through the large wooden bilge access panel.

Regarding ongoing maintenance, the pickup sponges need periodic replacement when they begin to deteriorate, at least annually in this prototype system.  Allowing the sponges to deteriorate could cause the tubing to become clogged with sponge debris.

A note about pickup-to-manifold tube sizing:  four different internal diameter tube sizes were tested, 1/16″, 1/8″, 1/4″, and 3/8″.  The 1/8″ internal diameter tubing yielded the greatest volume of water removed when one of the sponges was wet while one of the sponges was dry, which is likely to occur in this system.


  • Seaflo 1.2gpm diaphragm pump, available from
  • Generic 12v DC timer, available from
  • 3/8″ clear vinyl tubing, available from most hardware stores, used for manifold, and inlet and outlet to pump
  • Rubber stopper, available from most hardware stores, used  for capping end of 3/8″ suction manifold
  • 1/8″ clear vinyl tubing, available from most hardware stores, used for line from pickups to suction manifold
  • 1/8″ to 3/8″ plastic barb fittings, available from most hardware stores, used for sponge pickups, and at suction manifold
  • Household wall faceplates with center hole, available from most hardware stores, used for mounting sponge, and holding plastic barb ttings to 1/8″ tube
  • #12 fine thread stainless steel screws, available from most hardware stores, used for mounting sponges to faceplates, and mounting pump to bulkhead
  • #6 stainless-steal through-bolts with nuts, available from most hardware stores, used for mounting timer to electrical bulkhead
  • Cable ties, available from most hardware stores, used for mounting tubing to existing systems
  • 16 gauge wire, available from most hardware stores

A version of this article originally appeared in the November 2017 Catalina Yachts owners’ magazine, Mainsheet.


Dropping the Mast On a Catalina 25 (or Similar Boat)

Dropping the mast aft with a custom-built A-frame rig is popular among Catalina 25 owners.  Other Catalina 25 owners have good reason to prefer dropping the mast forward.  Rumor has it that Catalina intended for the mast to be dropped forward, which is why the factory specification for mainsheet length is longer than necessary to sail the boat.  Dropping the mast forward is convenient on boats with a bimini mounted over the cockpit.  Dropping the mast forward is less ideal for boats without biminis if the mast is only being dropped to motor under bridges.  Leaving the mast dropped forward but still attached to the mast step leaves the mast in a precarious position, and dangerous for navigation.

Dropping the mast forward requires no A-frame rig, gin pole, or other additional hardware.  Having an assistant is helpful for two of the steps but not necessary.  The boom acts as a gin pole.  The mainsheet tackle provides the leverage to ease the mast down and raise it.  The topping lift (or backstay pig tail attached to the aft end of the boom) counters the mainsheet.  Guy lines run from the aft end of the boom through the foresail fairleads around the foresail sheet winches to the foresail sheet cleats stabilize the boom laterally (See photo.), and importantly keep the boom vertical as the mast comes down.  Sail track stops, like those made by Davis, (or one sail track stop and the cleat for the downhaul) prevent the gooseneck on the boom from sliding along (and possibly out of) the mast track.


  1. Disconnect all wiring at the base of the mast.
  2. Fix the forward end of the boom in place using a sail track stop above and another below the gooseneck, or a sail track stop above and the downhaul cleat below.
  3. Put tension on the mainsheet and the topping lift so that the boom is approximately level and perpendicular to the mast.
  4. Move the foresail fairlead cars as far aft as possible.
  5. Run a guy line from the aft end of the boom through the port foresail fairlead, around the port foresail sheet winch (1-2 turns on the winch), and secure it on the cleat for the port jib sheet.  Run another guy line the same way, but to the starboard side of the boat.
  6. Disconnect the backstay.  For boats with adjustable backstays, first move the adjuster upward to ease the tension on the backstay as much as possible.
  7. Disconnect the aft-most lower shrouds.
  8. Loosen the upper shrouds with 7-8 turns (more or less) on the turnbuckle.
  9. Loosen the bolt at the base of the mast so that there is 1/4” of clearance between the nut and the mast step.
  10. Ease the mainsheet a few inches.  Then ease the port guy line a few inches.  Then ease the starboard guy line a few inches.  Repeat this process, carefully going from mainsheet to port guy line to starboard guy line, round after round, until the mast is down and resting on the bow pulpit.  Keep tension on at least two of the three lines at all times.
  11. Lash the mast to the bow pulpit to prevent it from sliding laterally off the pulpit.
  12. Ease both guy lines to determine to which side of the boat the boom will tend to fall.  One guy line will fall slack while the other remains taught.  Ease the guy line that remained taught until the boom is down laterally.
  13. Remove the upper mast track stopper, slide the gooseneck out of the mast track slot, and bring the boom inboard.
  14. Unlash the mast from the bow pulpit.  Having a helper do this step and ensure the mast does not slide laterally is convenient.
  15. Sit on the end of the boom (or wedge it in an armpit to hold it down) and remove the bolt securing the mast to the mast step.
  16. Carefully lift the end of the mast, and move the mast aft until the end rests on the aft pushpit.  Having a helper lift the mast above the pulpit while moving is convenient, and prevents scratching the mast and the pulpit.


  • All running rigging should be in good condition.  (Check the topping lift!)
  • If using the downhaul cleat to help fix the gooseneck in place, make sure the cleat’s mounting screws are tight.
  • Take it slow until experienced.  Of the three lines in play (two guy lines and the mainsheet), two of these lines should be taught at all times until the mast is down.
  • The boom may flop violently to one side of the boat or the other if the guy lines are not used.
  • The top of the mast will tend to tip into the water when the mast step bolt is removed, until the mast is carried aft.

This article originally appeared in the May 2018 Catalina Yachts owners’ magazine, Mainsheet.

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