Fresh Water System

September 04, 2016


The two fresh water tanks are located in the hulls where they are an integral part of the boat structure.

Two electronic water pumps, one for each water tank, pressurize the fresh water system.  During normal operation water is drawn from one tank only using its own pump.

Even when in a marina, where water is available, the boat uses the water tanks and pumps.  The marina water is only used to top off the tanks, and there are no provisions to pressurize the boat water system with the marina water.  This ensures that the water in the tanks is always used and kept fresh and that if a water hose on board should burst, the boat will not sink in its slip.

This picture is not up to date.


Turning on the Fresh Water System

The pumps to turn on or off the fresh water system are located on the bridge panel.  You can turn on either pump or both, but it is not recommended to turn both on at the same time.

Each pump has a breaker located in the corresponding starboard or port hull panel.

The Maretron display on the bridge shows which pump is active and the approximate quantity of water left in each tank in percentage.

Switching Tanks

To switch tanks turn off the pump in use and turn on the other one from the bridge panel.  There is no need to open or shut valves.

During long passages follow the procedure below to ensure that one tank is always full with good water.

During Long Passages

Never run both tanks dry, even with the watermaker.  Work the tanks and the watermaker in such a way that if the watermaker should fail the rest of the journey may become a hardship (no frequent showers) but not an emergency.

One way to accomplish this is to run one tank down to a third and then fill it with the watermaker.  When the tank is full, make sure that the water quality is OK and then switch to the other tank.  

Always keep an eye on the lateral trim of the boat!

Living on Board in a Marina

Change tanks frequently (at least once every two days) and if possible run both tanks dry before topping off the tanks.  This ensures that both tanks always contain fresh water.

Always keep an eye on the lateral trim of the boat!

Boat Inactive or Hauled Out

Turn off the electric power to both fresh water pumps.  Open the cold and hot water tap in the kitchen to relieve the water pressure in the water hoses.

If the boat is inactive for a very long time (more than four months) consider the possibility of emptying both tanks.  Never add Clorox or bleach to a tank since chlorine harms aluminum.


The watermaker requires special care to make the membrane last.

If the watermaker is to be left inactive for over two weeks, it has to be pickled with the special chemical furnished by Spectra.

To pickle the watermaker only use the special chemical furnished by Spectra.  Read the manual and follow the recommended procedure

To flush the pickled watermaker  read the manual and follow the recommended procedure or read the watermaker quick help.  Never run the pickled watermaker.

Never use the watermaker in a harbour with dirty or oily water.



June 12

Waternaker 102 hrs.
June 14 Go to Marina Croatia to get the two charcoal filters for the watermaker. 
Total cost E 70.00.  Marina buildings awful, nobody smiling.
June 15 Waternaker 119 hrs.  Changed all the filters.




Replaced port fresh water pump.  Problem with a bearing.
August 2 Waternaker 692 hrs  Replaced primary feed pump motor due to bearing failure.
August 13 Watermaker  Pickled 
September 2 Purchased spare fresh water pump, model without pressure switch


May 27

Watermaker 734 hrs  Turned on outside Genova
June 28 Waternaker Primary magnetic feed pump (next to control box) due to leaking gasket breaks.
July 11 Watermaker 852 hrs  New magnetic feed pump on one year old reconditioned motor.
One year old motor noisy, will have to be checked.  Otherwise everything OK
August 22 Watermaker 1010 hrs  in Porto Azzurro
August 25 Watermaker 1010 hrs  Pickled
August 25 Total watermaker hours for the year 276


May Reconditioned watermaker primary pump  on board as spare

May 18

Watermaker 1010 hrs  Turned on at anchor in Villefranche.
July 04 Waternaker 1033 hrs  in Genova, after France.
July 08 Watermaker 1061 hrs  in Marina di Campo.
July 11 Watermaker 1069 hrs  in Marina di Campo.
July 29 Watermaker 1113 hrs  in Portoferraio.
August 02 Watermaker 1130 hrs  in Bonifacio.
August 04 Watermaker 1141 hrs  in Erbalunga, Corsica.
August 25 Watermaker 1195 hrs  Pickled in Genova
August 25 Total watermaker hours for the year 185.



Water Tanks

The two fuel tanks are located in the hulls and are an integral part of the boat structure. On top of each fuel tank there is an inspection cover, used to inspect and give access to the tanks.  To seal the inspection covers, a thin film of grease is applied to both sides that come into contact followed by the polyurethane sealant 3M 5200.

Each tank holds approximately 650 liters of water, for a total of 1300 liters.

On top of the tank are welded  4 pipes, from bow to stern:

Water fill pipe.  42 mm diameter pipe going to the top of the tank.

Water out line.  18 mm inside diameter pipe going to about 100 mm above the bottom of the tank, so as to leave behind any small amounts dirt .

Water in line.  18 mm inside diameter pipe going to the top of the tank.

Water vent pipe.  18 mm inside diameter pipe going to the top of the tank.


Each tank has been tested with water pressurized to 0.2 bar.

The inside of the tanks have been painted with 2 coats of food grade epoxy paint.


Fresh Water Pumps

The two pumps used to pressurize the fresh water system are Jabsco PAR-MAX 4 pumps.

Multi-outlet automatic water pressure pump serves up to four 1/2" outlets at once.  Diaphragm design allows it to run dry without damage and thermal overload protection automatically stops the motor if it overheats.

16 liters per minute, built in 40 psi pressure switch, self prime to 3 meters, made of glass filled polypropylene.
Draw 15 A @ 12V DC maximum, 7 A@ 0.7 bar.

The problem with these pumps is the electrical connection to the pressure switch.  The two connectors to which the fastons attach get corroded.  The only solution is to solder the two wires to the connectors.  Also unfortunately after some years the connector fail.  The only solution is to add an external pressure switch to each pump.

To avoid the pressure switch problem and since each pump now has an external pressure switch the model without pressure switch if possible is purchased.



Jabsco PAR-MAX 4 pump Jabsco model 3162-0092
1 Jabsco PAR-MAX 4 pump, no pressure switch Jabsco model 31705-0

The following manual provided by the manufacturer is also part of this section:

Jabsco Par-Max 4 manual


Pressure Switch

Unfortunately a separate pressure is required, even though the Par-Max pumps have a built in pressure switch.  The problem is that the connections to the built in pressure switch corrode after a few years and become unusable and impossible to fix.



Square D pressure switches, 2.5 bar model 9013FSG2


The following manual provided by the manufacturer is also part of this section:

Square D pressure switch manual


Water Pipes and Hoses

The fresh water system uses Hepworth Acorn pipe and fittings of 15 mm outside diameter.

The plastic pipes withstand a temperature of 82 deg. Centigrade and a pressure of 3 Bar.


Hepworth plumbing UK


For all the flexible connections food grade plastic hose with a synthetic netting is used.


Plastic hose ID 15 mm, OD 21 mm  


The following flexible pipe sizes are commercially available:

Inside Diameter (mm) Outside Diameter(ID) Max. Pressure (Bar)
6 12
8 14
10 16
13 19
15 21
19 26
22 29
25 33
30 38
32 42
35 45
38 48
50 62


Deck Fill

The deck fills for water are made of molded nylon.  The caps are blue and replacement caps are available.



Sea Dog water deck fill


Water Maker

The Spectra 300 MPC is a very efficient watermaker running on 12 V DC and thus can be left on when under way with only the engines running.

The water maker feeds only into the port water tank.

The two hoses to pickle the unit are behind the hot water boiler.


spectra watermaker
If the prefilter pressure displays an error, try to clean the pressure sensor inside the small hole.
Or try to invert the two pressure switches.

If the salinity reading displays an error, clean the oxidation off the probe with a fine sandpaper.


Spectra CAT 300 MPC Serial # CT300MPC/12V/0309

The following manual provided by the manufacturer is also part of this section:

Spectra watermaker manual



cat_12_e fresh water.htm