Both Britannia’s heads are Raritan “Elegance” electric models, which I installed nearly four years ago, and they have performed flawlessly thus far. A principal reason for this is, for about 90% percent of the time they are flushed with clean fresh water.

The corrosiveness of sea water is well known to sailors, and the filthy brackish water in the Intracoastal Waterway does not help either. Even “clear to the bottom” seawater conditions do not prevent calcification of the pipes and valves, or its frequent offensive odor. It isn’t so much human waste which causes the foul stink commonly emitted from marine heads, but sea water born micro-organisms which die in the pipes and are then pumped into the bowl, usually on the first flushes after a period of none use.

Flushing marine heads with fresh water obviates these problems and most manufacturers recommend sea water flush toilets should be flushed with fresh water occasionally, especially when leaving the boat for any length of time. This also prevents that nasty brown ring in the bottom of the bowl.

My heads were originally raw (sea) water models, but I then devised a modification which allows them to be easily interchangeable between fresh water and sea water flush. Raritan offers a kit which converts a raw water flush toilet into fresh water flush at the press of a button. It operates very similar to my method, but does not have the one way check-valve or a shut-off valve like my system. The factory system is also specific to the Elegance head. My method will work with any marine head, whether electric or manually operated, because it is fitted on the incoming pipework, not in the actual body of the toilet, like Raritan’s installation. It also costs $190 when my equipment cost $80

My objective in devising this system was to be able to flush the toilets with fresh water from either a marina shore water supply, or the boats potable water tanks. But when converting back to raw water, to ensure the boats fresh water system is totally protected, both automatically and manually, from any incursion of sea water.

The solenoid prevents seawater entering the freshwater lines.I achieved this by using a 12-volt stainless steel water solenoid valve, which is normally closed and watertight by default, and only opens when current is applied to it. Not wishing to rely entirely on this mechanical/electrical device to prevent back flushing I also incorporated a manually operated ball shut-off valve, along with a one-way check valve as a third protection.  All this is in addition to closing the sea water sea-cock when using fresh water flush.

Like most boats of her size, Britannia has an on-demand electric pump drawing from her fresh water tanks and pressurizing the boats complete water system. Basically I interconnected this supply to each of my two heads, so when the solenoid valve is activated the toilet flushes with fresh water. The method can also be used to flush manually operated heads with fresh water, even if the boat does not have a pressurized system.

When in a marina I usually connect to the pressurized dock-water supply with a water hose to a pressure reducing regulator into the boat. I can then switch the electric pressure pump off and have constant silent water pressure throughout the boat, including the heads. I have also incorporated an automatic solenoid shut off to this water inlet in case of an internal pipe failure.

Even when under way I normally leave both heads on fresh water flush, especially in the ICW and short passages elsewhere. But then Britannia has a very large potable water capacity, (325 US gallons), and it will depend on the capacity of your fresh water tanks, and the number of people using the heads, as to whether you change over to sea water when on a passage.

A urine flush uses about a quarter of a gallon of water in Britannia’s heads and a full flush about three quarters of a gallon.

This is the control panel for the Elegance toilets.Normal sea water operation:

Pressing a button on the control panel in the bathroom activates a dedicated raw water diaphragm pump, which draws sea water from a hull sea-cock, through a filter and into the toilet bowl. Manual toilets are the same, except sea water is sucked in by operating the toilets hand pump.

Fresh water flush:

After physically changing the valve and pump connections the actual flushing operation is the same as for sea water, except the boats fresh water pressure pump now pumps water into the bowl, (or it comes in pressurized through the dock supply). In the case of a manual head, fresh water is sucked in with the manual pump instead of sea water.


This is easier to actually install, than it is to describe. There are three components.

A plastic one-way check valve and a regular ball shut-off valve can be bought from most hardware stores. I bought the 12-volt solenoid from, who also have a 24-volt version. See pricing below.

First I tested the one-way check valve by connecting it to a dock water hose. In its flow direction water flowed without restriction, but when connected to the opposite end of the check-valve absolutely no water came out. That’s how it should be.

This is the valves which prevent freshwater contamination when the toilets are on seawater flush.This shows the components to allow both seawater and freshwater flushing.I then connected the parts together into an in-line assembly, consisting of the solenoid, the shut-off valve and the one-way check valve. Then I connected them, using tee connectors, between the boats cold water system and the sea water inlet pipe which feeds each toilet. You can see in the picture that the manual ball valve is connected next to the toilet pipe, then comes the one way valve, then the solenoid. This arrangement ensures that when in raw water flush mode no sea water can ever get to the solenoid and never percolate back into the fresh water system. The installation is under an easy to reach floor-board. Interconnecting the pipes would be just the same for a manually operated toilet.

A 12-volt wire comes from the toilets control boxes and normally activates the sea water inlet pumps. I fitted this with quick-change connectors on the pump and solenoid wires. When on sea water flush mode the wire is connected to the sea water inlet pump, but when using fresh water the wire is changed over to the solenoid. The two negatives (returns), from the pump and solenoid go to ground. I actually considered making this wiring connection using a double pole, double throw switch, (which is what Raritan uses), mounted somewhere near the toilets. But since my system has the added safety of the manual ball shut-off valve it is necessary to physically open and close this valve to change the flushing method. I therefore decided it was just as easy to switch the pump and solenoid power over at the same time. This means one less switch to go wrong, and it’s not as though we change the flushing method frequently.

In the case of manually operated toilets it is only necessary to connect the solenoid to a straightforward 12-volt supply, through a switch near the toilet which can be permanently connected to the solenoid, since there is no pump on a manual head. When the valves are turned to fresh water and the switch is activated the solenoid opens and permits fresh water to be drawn into the bowl using the hand pump on the toilet. When switched off the solenoid closes again.


To change over from sea water to a fresh water flush. (1) First the sea water inlet sea-cock is closed, (2) the wire from the sea water pressure pump in changed over to the solenoid. (3) the fresh water supply ball valve is opened.

On manually operated toilets operation (2) is not needed because there is no pressure pump and the switch to the solenoid can be permanently connected.

When the control panel button is operated, (or the switch in the case of a manual head), the solenoid instantly opens and the water pump (or shore water pressure), pumps fresh water into the bowl, exactly the same as if a washbasin faucet has been opened. It takes only a few seconds to fill the bowl and when the button is released the solenoid closes and the water stops.

A manual toilet would be pumped by hand, and after flushing the switch would be returned to ‘off’ and the solenoid closed.

To switch back to sea water flush the process is reversed. (1) The fresh water ball valve shut-off is closed (2), the electrical wire from the solenoid is changed over to the sea water pump, (3) the sea water sea-cock is opened.

Fresh water flushing has a great secondary advantage, but which will only be appreciated when it comes time to dismantle the head to install new parts or replace pipes, (which is as certain as the wind is always on the nose). You will no longer need an oxygen apparatus to do the job!

I consider fresh water flushing to be a major improvement to a very necessary, but often neglected, (until a problem occurs), piece of my boats equipment.


The electric toilet in the forward head.