Team Windcraft – Making fresh water on a Hanse 400 with a Rainman desalination unit

Originally posted on Team Windcraft website by Mike Quinn, April 2015.

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One of the most frustrating things when cruising, is the need to go into marinas regularly to fill up with fresh water. The more people you have on board, well, 330 litres of water just doesn’t seem to last that long without rationing does it!

For the last few years I had looked at various options to install a watermaker on Mica, our Hanse 400e. The high cost, relatively low output and complexity of installation had always put me off.

However, a manufacturer has finally come up with a product that overcomes all these barriers.

The first time I saw the Rainman Desalinator was at the Sydney Boat Show last year – straight away l knew l had found my solution!

At that stage, the product consisted of a self- contained pressure supply unit fitted with a small petrol driven Honda motor.  A choice of reverse osmosis tubes gives different fresh water outputs.

Not long after, Rainman launched an electric pressure supply unit that runs on 240 volts and can be powered by a 2KW inverter or a Honda 2 KW generator.

I already had a Honda generator on my Hanse “Mica” so this was the option I selected

The reverse osmosis (RO) tube is what contains the membrane that separates the salt from the pure water.

The ‘economy’ RO tube is just over 1m long with quickfit connections for the high-pressure input supply line, the pure water output hose and the pressure control valve to which the waste water output line is connected.

I took some quick measurements and found that the pressure control unit would fit in my deep cockpit locker, along with the Honda Generator.

The blue pressure supply unit in the locker (where it stays, even when operating). The Honda generator on the transom.

The above picture shows the blue pressure supply unit in the locker (where it stays, even when operating). The Honda generator sitting in the cockpit, connected to the pressure supply unit, and the clear salt water intake hose running from the pressure supply unit over the back of the transom and into the water.

The reverse osmosis tube could be mounted in the rear cabin underneath this locker, largely out of sight, with only the pressure gauge, valve and output lines visible.

RO unit mounted in aft cabin underneath the deep locker in which the pressure supply unit is stored.

The high pressure supply line – that connects to the pressure supply unit – simply passes through a hole drilled in the side of the locker inside the cabin which allows easy connection to the pressure unit.

To make fresh water now – all we have to do is – attach the pressure line that connects the RO tube to the pressure supply unit, lift the Honda out of the locker and start it up, put the salt water intake line into the water (just drop it over the transom), plug the unit into the Honda and turn it on.

As soon as the pressure valve has adjusted to operating pressure, we are making fresh water in a matter of minutes! The waste water line simply goes over the side of the boat and the fresh water line popped into the water tank filler when the water is no longer salty.

Rainman in operation – here the unit is running with the white hose supplying fresh water into the bucket.

We can now make 50 – 70 litres of fresh water per hour with little fuss. No more interrupting our ideal anchorage or passage by having to go into a marina to get more water!

Another shower anyone?



April 28, 2015 at 7:15 am

Hi Mike,

Just in time for this year’s cruise North! I have heard a lot about the Rainman so great to see it actually in place on a Hanse . I understand it a lot better being able to see the various parts fitted on Mica.

More water means more freedom when sailing! Thank you and happy cruising.

Readers will be interested in an earlier post on this blog


Helpful Links

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» View details on Rainman AC watermakers

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» Contact the Rainman team should you have questions about our marine desalination systems