Keeping the bilges dry

This is a technical post I've written because it will be of interest to other Boréal owners. You have my permission to skim read it!

Vagrant came out of the factory with four Whale Orca 1300 electric bilge pumps and a manual one. The forward sail locker and aft lazerette are separate water-tight compartments, so each has an Orca pump. The remaining three pumps serve the central living area. I've added a sixth one. Why on earth is it needed?

The electric bilge pumps are in the centre of the boat and serve two separated bilge sumps, one on each side of the centreboard trunk. These pumps rapidly clear water from the sumps, except for the last two or three litres. Their inability to pull out the remaining water is partly due to the pump design but also because the outlet pipe goes overboard a metre above the water line, via a check valve. When the pump is switched off, the water before the check valve back flows back to the sump. Consequently the sumps are never fully dry.

The starboard sump is under a hinged step and can be cleared easily using our fantastic DeWalt wet and dry vacuum. The port sump is less accessible: to drain it, I must empty our pan cupboard, remove our Ecor Pro dehumidifier, and climb down two levels.

Way Down in the Hole

Vagrant is generally a dry boat, barring self-inflicted watermaker and plumbing accidents. We'd really like the sumps to be bone-dry as well. The port sump usually sees the most water because the anchor locker drains into the sump, so takes a bit of water if we're bashing to windward and have been too lazy to plug the anchor pipe. Also, the dehumidifier vents moist air into the anchor locker and some of it condenses back to the bilge.

Fortunately, I'm not the first to face this problem. The typical solution is to complement the bilge pump with a diaphragm pump to drain the last drops. My solution closely follows this one by Seth Pool, except I didn't bother with the automatic timer. I also wanted to use whatever I had in my spares lockers, the most useful thing being an old Johnson Pump WPS 24 water pump that I was keeping for a rainy day. Its integrated pressure switch is unnecessary, but otherwise it fits the bill nicely.

A quick lash-up gave me confidence that the system would work. Because the tubing is small diameter, there is no problem with the height through which I needed to lift the water, and the pump self-primes easily. The rest of this write-up will cover the installation in three parts: creating the outlet to route the water overboard; creating and mounting the bilge pick-ups; and mounting and wiring the pump. Please refer to Seth's article if you want more background.

The drain

How to get the water overboard? I wanted to avoid touching the plumbing for the existing bilge pumps since they are a safety-critical system. On a Boréal, several tank vents are routed to the top of centreboard trunk which is conveniently situated between the two sumps and right below the primary switch panel.

Tank vents in top of centreboard trunk

On Vagrant, from left-to-right in the above image, these are the vents for the port-hand water tank, the grey water tank, the forward heads black water tank, the starboard water tank, and finally one of the vents for the diesel fuel tank. Each pipe comes from the tank, up in an anti-siphon loop to deck level, then back to the top of the case about a metre above the water line. Given the siphon loop I really don't see the choice matters too much, but thinking of bilge water in the domestic water tanks or worse, the fuel, I decided to tap the outlet into the grey-water tank vent. First, I checked I had the right pipe (blow into it, you can hear the bubbles in the galley sink). I connected it with a tee-piece without cutting the original pipe so I can easily remove it if I change my mind in the future.

Tee'ing into the grey water vent

The pick-ups

Next, on to the bilge pick-ups. Seth Pool's idea of using a Scotch Brite pad is clever. The sponge collects stray water as the boat moves and acts as an effective filter to keep crap from blocking the inlet. I was a little sceptical that a tube with holes in it would suck through the sponge, but it works fine.

I had some stiff, small diameter plastic tube left over from the watermaker installation, so I used that. I drilled some fine holes in one end of it and inserted it into the sponge. Making a hole in the yellow sponge is difficult - a drill bit doesn't work. For the second pick-up, I hit upon the idea of using a soldering iron which works much better.

Note the small holes in the tube

 

Tube inserted into the sponge

Boréal mount the bilge pumps on aluminium plates so they can be lifted out easily. I made a bracket to mount the pick-up to the plate. Here's what that looks like for the starboard sump:

My metal-bashing work bench

A cable tie holds the sponge, and also goes around the tube

Installed in the starboard sump

Routing the small diameter tube from the starboard sump required some furniture disassembly. It proved impossible to find a route past the insulation with a fish wire, but once the cabinetry on top of the centreboard was removed, it was easy. 

Routing the pick-up tube to the starboard sump

 

You'll see in the above image that I also removed the step for ease of access while I was working on the starboard sump. It took me a while to realise that the hinges are attached using machine screws with dome nuts. But it's a boat job, so has its challenges. Such as the royal mess you make of the boat when you have to get the top off the centreboard.

Boat life

The second pick-up in the port sump is similar. The hose is easier to route to this sump.

Pick-up installed in the port sump. The black hose is for the dehumidifier drain.

The pump

The final step was to mount the pump and connect it up. The pump fitted nicely on the forward side of the bulkhead below the electrical panel cupboard, to port of the centreboard trunk. Here it is at the same level as the drain and not too close for the plumbing to be uncomfortable. The only challenge was reaching down through the access panel and to the left while holding the pump and fitting four screws. I tried and failed to use its anti-vibration feet and in the end bolted it straight to the bulkhead with penny washers bridging the holes.

In a pleasant contrast, the wiring to a spare panel switch was easy. I didn't even need to extend the pump cables – they were exactly the right length.

Wiring the panel switch.
The pump is not visible in this image, but is mounted through the access panel to the bottom left.

In use

We've been using the pump for a few weeks now. It does a very good job, and leaves the bilge dry - even more so if the boat moves a bit so the sponges can collect the last few drops. Understandably, this is a slow process and the pump has to run for some time. We are developing the habit of switching the pump on whenever we drain the grey water tank; so about five minutes every day.

However it's apparent that if one of the sumps is dry, vacuum is lost to "sucking air", and the other sump drains much more slowly, if at all. When I checked yesterday, the starboard sump was bone dry, but the port one still had a litre or two of water, and to drain it fully with the pump I had to crimp the starboard tube closed. I am now planning to put in a diverter valve so I can select which the pick-up to use. Because the plumbing is all behind the scenes, I'll use a solenoid valve wired to one of the panel switches.

All in all, this has been a successful and rewarding project, and Vagrant appreciates her dry bottom.