The positive view of removing seacocks

So I’ve written loads on seacocks already:

But these have mostly been written from the negative side (why we think seacocks are bad and the problems we have with ours). Here I want to write about why a boat with few seacocks is a really positive thing:

  • Less Maintenance
  • Fewer Smells
  • More usable space
  • Fewer significant points of failure
  • Cheaper
  • More cruising grounds

I suggest that these are not automatically all true if you simply get rid of seacocks, they do depend on the other decisions you make.

So this is where our plans are now.

Each sink/basin (galley and 2 head compartments) will have it’s own smallish grey water tank underneath it. That will be all we have for our first year during which we will use a portable electric pump with long hoses to empty these tanks. Later we will add a large common grey water tank. That will have a “proper” pump out fitting on the deck so we can empty it at any official point. Initially we will move the water from the individual tanks into this with the portable pump, later we will plumb in a fixed solution. Only then will we fit a shower pump directly from the sump to the main grey water tank.

We are replacing both direct discharge toilets with composting toilets.

We are not having a salt water intake for washing up.

When we replace the diesel engine with an electric motor we won’t need a cooling water intake.

That means we are heading to having 2 below the waterline seacocks (for the 2 cockpit drains). Providing we fit the cockpit cover whenever we leave the boat, I think we can safely leave the boat on a mooring/at anchor/in a marina with zero open seacocks.

In order to see how all these advantages come from this setup we need first to look at the alternative(s).

The alternative

We need to be clear that doing nothing was not a valid option, for lots of reasons. So to start with the galley waste water hoses were blocked:

Simply replacing these hoses would still not allow us to cruise in Turkey (and we assume other countries will follow their example). We would need grey water tanks adding to the system.

The toilets could not be used while ashore or in the coastal waters of most countries or in any canals because they didn’t have a holding tank. “Upgrading” the original toilets to have holding tanks would have been very expensive. In the process all the existing hoses would have had to be replaced. The pumps were also very rusty. Finally it would have been technically very difficult as it is hard to see where a holding tank could be fitted for the aft heads.

Beyond all that expense and work, with what I know now, it would have needed to be in our plans to replace all the seacock bolts before cruising very far. Depending on whether you are able to get Phosphor Bronze bolts or not the price could be around £500, just for the nuts and bolts.

So to be able to cruise with the existing seacocks we would have need to add grey and black water tanks, with new hoses, valves and pumps. We would have needed to spend money on all the existing seacocks.

So the benefits

Less Maintenance

We now have 8 fewer seacocks (eventually 9) to maintain and to close when not needed.

We have no black tank (raw sewage) and no sewage pipes to maintain

With both the grey water and black water tanks we don’t need any diverter valves and the amount of pipes/connections is much reduced.

With the intermediate small grey water tanks we catch the bits (like hair) before they block pumps) so they will clog less often (because we will pump out with a hose with a filter put in from the top of the tank).

Fewer Smells

No sewage pipes. No sewage tank. No sewage valves. No pumping dirty sea/river water into toilets to flush them. All this keeps smells away. Composting toilets simply smell less and are easier to keep clean so that continues.

Also being able to build the head and shower areas so that there are no holes to provide access to seacocks makes it easier to create spaces that are easy to clean with no inaccessible places for waste to collect and smell.

More usable space

This one has surprised us a little. The Nature’s Head toilets are larger than the originals so we assumed space was going to be tight. However, we have found that far more space was taken by all the hoses and seacocks (plus access to them) that we are going to be better off for space.

Also we don’t need to find space for any black water (sewage) tanks.

In the galley much of the potential cupboard space was lost to all the pipes and seacocks. While the grey water tank will take some space much of it will be below the original floor which was unused.

Fewer significant points of failure

When you have seacocks and valves controlling where the flow goes there are multiple really significant points of failure. Any break in a seacock, hose or valve has the potential to sink the boat or to release a tank of waste into the boat.

With our system there are no connections below the waterline,, there is no failure that can lead to the boat sinking. There is no sewage tank or hoses so nothing to leak. By having separate grey water tanks with a manually controlled pump to move grey to the main tank there are no lengths of hose filled by gravity that can leak when unattended.

If the pump fails then we can manually pump out the individual tanks. We also have them available as a simply gravity drain for each sink/basin if we have a power failure.


On the toilet side of the system there are savings on no black water tanks, no hoses, no diverter valves, no new seacock bolts. Against that there is the (significant) cost of the composting toilets.

On the grey water side we are trading more tanks for simpler hoses and no valves (and no seacock bolts).

Probably not very different in the need for electric pumps as it is unlikely that we could have managed to get flows from all 3 basins/sinks into a central holding tank by gravity alone.

Our system is going to be much easier to install piecemeal and the costs (apart from the toilets) can be spread out. Overall there is much less to install and what we do install is simpler.

On the other hand you could have done minimal replacements and not put any tanks in. However, that would restrict your cruising area and go against our sustainability goals.

More cruising grounds

We do not want to rule out cruising to Turkey nor going to the Mediterranean through the French canals. We would expect that as more countries take pollution more seriously that boats without the ability to demonstrate that they are not discharging any black or grey water will be more and more restricted.


We started with a couple of beliefs.

  • We should not be pumping raw sewage into the sea from toilets. For us using a holding tank to keep the sewage until you are away from land and then pumping out in bulk is also not acceptable (and the storage plus disposal are very pleasant when things go wrong).
  • Holes under the waterline always increase risk, however, slightly.

It has been good to discover that trying to be sustainable is (again) also better for our quality of life. I can’t imagine why, if faced with a significant refit, anyone would choose to spend money to continue to release black and grey water into the sea.

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