Our seacock plan: tending towards zero

I’ve written a massive post on seacocks already “Refurbish or replace: Seacocks?” Plus I made a video looking at the underwater features of Vida, in particular all the seacocks.

As you may have seen in “Friday progress #5” we have now removed all 3 of the seacocks for the aft head. This is because we now have a PLAN!!!!!

We are going to be getting rid of 8 seacocks and one additional hole below the waterline. We believe that this will make life much simpler and safer in the future. So…

Composting toilets

We are fitting 2 Nature’s Head Composting toilets. That saves us 4 seacocks (each toilet had a flush inlet and a flush outlet). Not only that but the smell and convenience is massively better plus of course they are infinitely better for everyone else. For the last 42 years Vida has been pumping raw sewage into the sea anytime the toilets were used. One option to be legal in more countries would have been to add a black tank to store the sewage (typically until away from the coast when it would be pumped out in bulk). This way we dump nothing in the sea when away from home for less than a couple of weeks. Beyond that we hope to carry a large enough container to make sure that solids are fully composted before disposal. At a very minimum they will be partially composted and so much less polluting when disposed of ashore or at sea.

All 4 of these seacocks will be properly filled with glassfibere cloth and bio-epoxy resin.

Galley sea water inlet

We are going to re-purpose this hole for a fridge keel plate cooler. This is the most efficient way to cool a fridge and the hole is fully, permanently plugged. That saves us 1 seacock.

Galley sink and aft head basin

Instead of these having their own seacock we are going to upgrade the seacock and hose for the port side cockpit drain. The cockpit drain hose will then have a branch off it which the two drains are attached. That saves us 2 seacocks.

Forward head basin and shower

The shower is supposed to have a pump. We will fit a new automatic electric pump for the shower sump. The hose for this will join the galley and aft head basin by draining into the port cockpit drain.

The forward head basin will drain into the shower sump where the automatic shower pump will pump it out. Obviously that means every time you wash your hands either a small amount of water will be sloshing around the shower sump or the pump will come on. If this proves to be annoying (sound of a pump in the middle of the night or water sloshing out of the sump in rough seas) then one option is to fit a small grey water tank under the basin. In calm conditions when everyone is awake this can be drained into the shower sump and pumped out in one go. This saves another seacock.

Speed paddlewheel

We will remove this and fill the hole. For the moment we will reply on a variety of different devices providing speed from gps signals. Saves one hole.

What’s left

Two cockpit drains with seacocks (the port one will also be draining the aft heads basin, the galley sink and the shower sump from the forward heads).

Engine water cooling inlet.

Fixed depth sounder sensor, assume we will leave this for the moment.

Safety when unattended

With these changes we will be able to shut off the engine cooling inlet whenever we are not on board (indeed whenever not using the engine).

However, as it stands the two remaining seacocks for the cockpit drains will need to be left open all the time. They only get closed if there is a problem with the hose when you turn them off to stop flooding. You can’t close them at any other time in case water gets into the cockpit and fills it up (rain for example if the cover isn’t fitted properly or gets blown out of position or whatever).

So we are going to fit a hose above the waterline that connects the port cockpit drain to the bilge pump seacock (which is above he waterline). This will have a seacock on it that is closed when sailing. Whenever the boat is left at anchor, on a mooring or in a marina the two cockpit drain seacocks below the waterline are closed (so there are zero open seacocks below the waterline) and the connection to the bilge pump seacock is opened. If (very unlikely) water gets into the cockpit it can now run out of the bilge pump seacock above the waterline (this wouldn’t work when sailing as on the port tack water would have to uphill to get out of the cockpit).

The future

The long term goal will be to replace the diesel engine with an electric motor to cut fossil fuel use. When that happens the engine cooling inlet can be reused as the water inlet for a watermaker (converts salt water to drinking water).

That means we are looking at going from 13 holes below the waterline to 5 of which 2 are permanently installed devices (fridge cooling plate and depth sensor) and 3 area going to be new composite seacocks. One of those will only be open when running the watermaker (about once a week). The other two can be closed whenever we are not on the boat. We will be fitting Trudesign Monitored seacock valves which means that we will get a light at the main control panel to show the current status of the seacocks (so that we don’t forget to open/shut them as needed). These composite seacocks will also avoid any future issues with corrosion, especially galvanic caused by electrical currents and dissimilar metals.


Even with these precautions problems can still occur so we will be upgrading our pumps and they will include a fully automatic electric bilge pump that will sound an alarm (and send out phones a message) if it comes on.


We might be called paranoid by many. Our view is that every extra seacock requires maintenance and is a potentially critical point of failure. We’ve heard claims that the most frequent cause of boats sinking at their mooring/anchor is a seacock failure. Plus we want to be sailing not greasing seacocks 🙂


Two things that we should factor in.

  • If the cockpit filled with a wave the water pressure might cause water to go from the cockpit drain up to the sinks (which might be lower than the floor of the cockpit depending on what tack you are on). A check valve would help but then you are adding complications.
  • Hoses that go longer distances, particularly if they go through bulkheads are more likely to wear through and leak.

These might indicate keeping one or more seacocks for the sinks/basins. However, another option would be small grey water tanks that get pumped out above the waterline.

More thought required but my preference (for the small cost compared to the risk) would be for new composite seacocks rather than the old blakes ones – where new bronze bolts are very expensive and hard to be sure you are getting the real thing.

Update 2

Look at Amel yachts for systems designed to minimise seacocks with a large common sump for all grey water.

I understand that some Scandinavian boat building specifications require outlets to be above the waterline due to concerns with sea ice.

4 thoughts on “Our seacock plan: tending towards zero

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