Does everything have to be on tap?

Scott Dawson of H2O Innovations explains: “A lot of offshore racing boats now are taking desalinators instead of having larger tanks, in order to reduce weight.”

It’s a good point. Water weighs approximately 1kg per litre. Storing minimal amounts of water and being able to make more as needed each day reduces the weight and draft of the boat, which saves fuel and allows more space for storage or fuel tanks – which can mean longer voyages or simply more room.

But this wouldn’t have happened if the watermakers hadn’t developed in two ways. Firstly, becoming a lot more reliable and secondly, dropping the energy requirement, a point that Mr Dawson explains is down to the efficiency of pumps like the Spectra Intensifier units. “You do need about 800 psi to make a desalinator work, but these pumps recirculate the pressure back into themselves from the system so you don’t actually need too much energy to keep the pressure topped up. The 12V ones use 9A – in terms of energy it’s about the same as the autopilot.”

The reliability factor is possibly more central to the argument. Peter Middleton of Atlantis Marine, manufacturers of the Aquafresh brand of desalinators, says that the membranes themselves have become tougher. He explains: “The development of the manufacturing side has evened out the variability of the membranes, and productions rates have become less diverse. Whereas previously you might see one membrane giving 30 litres of water per hour and another from the very same batch producing a third less, all now hit the same 30 litre performance.”

Lindsay Ross of Fischer Panda adds: “They used to be high-maintenance, pernickety devices, but with the onset of auto freshwater flushing, water lubricated high pressure pumps and networkable operating data they are becoming more and more like high-end domestic appliances.”

If in trouble
However, though they have become very robust, there can always be failures, even if they are not actually the watermaker itself. Mr Dawson explains that when he is fitting a unit, he is very keen on showing how to get around things like the electronics – which are sophisticated, but at the end of the day, can be bypassed if there’s a real problem.

“Electronics don’t like water, or power surges,” he explains. “Inevitably, there is going to be one that goes wrong at some point, when a boat is halfway across the Atlantic or in some kind of difficult situation.” For example, in one case an unpowered craft found the charge cycle on a solar to battery system failed, which meant the watermaker didn’t work.

“However, there was something else aboard with a battery which was cannibalised and linked straight into the pump. This got the desalinator working again,” said Mr Dawson.

He adds: “Further, if push comes to shove it possible to get something like the bilge pump to act as a feed motor to push water through the watermaker, and this will keep a boat going till help arrives.”

Mr Dawson concludes: “There are always ways round difficulties, especially since you don’t need all that much power. Although these systems are robust it is only sensible to have ‘emergency plans’ up your sleeve, even if you never need them.”

Be realistic
There are other cases for fitting a watermaker. If, for example, you are looking at equipment for a craft liable to go to places where there is a definitely limited supply of water – at least the stuff you’d drink anyway – then yes, a watermaker could be a good idea. “Water is getting increasingly expensive in a lot of places, and it’s going to be a problem that gets worse...” says Mr Ross, adding, “water is definitely a growth industry”.

On the other hand, Mr Middleton points out that attitudes to water vary, usually dependent on what’s available. “While a couple going cruising on their own might get by on 5-6 litres a day, once people have the capacity onboard, it gets used,” he says.

It’s not just that water may be expensive to buy. After all, to be realistic you still have to evaluate the cost of a desalinator with the effort of getting hold of clean water supplies: many boaters might legitimately think “lovely idea, but actually I rather like the walk into town, and for this money I can get an unlimited number of taxis back”.

However, there are some areas of the world where most easily available water is really very nasty stuff, and for some, there are definite advantages to reducing the risks of bacterial and virus attacks. So, if a boater has chosen to cruise extensively in theses places, there’s a couple of important questions to answer.

Firstly, yes, in some places its hard to get freshwater without paying through the nose for it, but even if you are surrounded by seawater, is that itself going to be clean enough to let in through to the desalinator? Some manufacturers’ warn against running the watermaker within two miles of the shore, or in harbours or marinas.

However, it’s not because there will be any nasties coming through – they can’t get past the 5 micron filter or the oil water separator – but these filters do clog up, and are expensive and time consuming to keep replacing. They also cause the machine to shut down, adds Mr Ross.

Mr Dawson says it’s mostly a matter of common sense: “Generally just looking over the side gives a good indication of what’s coming through the filter. If you can’t see a metre down – don’t put the watermaker on.”

However, certain systems now have back-flushable options that help protect the particulate pre-filters, even if you are in estuary waters. Mr Ross explains that Sea Recovery and HRO provide a number of choices, including sand and multimedia pre-filters plus oil and water separators that deal with any slicks encountered – hydrocarbons, even in small quantities, destroy RO membranes.

Maintenance
Most larger watermakers these days come with a main back and forward flush to keep the system and the membrane itself nice and fresh, although boaters have to work out that they actually have enough in the tank to run the cycle, as it usually requires a few litres of production water.

However, Mr Middleton is slightly sceptical about the rigour of the backflush regime, and says that he doubts if a boater had used a non-backflush watermaker for a couple of seasons, whether then he’d think it worthwhile to retrofit one.

He adds that although the general advice from years ago still stands: “Flush through after five days without use, pickle it if leaving for 20”, he says that the watermakers have become a lot easier to keep in good condition and boaters do seem to be able to get away with longer timescales in between attending to them “with luck” – although it does depend on the climate, as bugs obviously breed a lot quicker in warmer conditions than in the cold. “There are some boats with Aquafresh units onboard which spend most of their time in the arctic, and they don’t actually seem to do much in the way of attending to the membranes at all,” he says.

Mind you, if the boat is going to be left for a while and has access to a dribble of power, then maybe leaving it on is the best option, as Mr Dawson explains: “These things love to run, its intermittent working they don’t like.” If its just not possible, then yes, the owner should really be looking at pickling the membrane to make sure the nasties don’t build up and leave a really smelly clean up to do. Not ideal as cleaning involves a mild acid solution, so it shortens the life of the membrane.

However, there is a hidden danger to make customers aware of – if the owner has left it for overwintering, for example, and pickled it with a recommended solution (and these vary from manufacturer to manufacturer) you can’t then simply clean the system out with chlorinated water. “It will destroy the membrane – and that’s expensive,” says Mr Dawson.

A number of the larger systems, like Spectra’s Newport series or the HRO units for example, now have a charcoal filter in the tank end. Besides taking any lingering odours out and sweetening the water, this also means that the tank can be filled directly, as it will remove the chlorine before the system brings in water in to wash itself down.

Independence
Beyond the overarching advantage of total independence, says Mr Ross, there are other issues. For one, he argues that an on-board desalinator can work out to save money in the long run by washing the boat down with potable water regularly.

“Salt and even dock water leaves spots on the gelcoat. It starts with a light stain which gets deeper over time, eventually the deposits start to degrade the surface coating,” he says, adding, “The glass and brightwork can also be affected too – and although it is only superficial damage, keeping a boat looking good does mean that it keeps its value for longer.”

It’s also worth noting that some, like the Sea Recovery watermakers, can be linked to any bridge control system that is NMEA 2000 compatible. This means you can control, monitor and programme the watermaker via the BUS network. In the right circumstances you can even fill your tanks before you get to the boat.

Waterway fresh
If you either have an inland liveaboard, or are intent on a lot of sailing in places where drinking water comes at a price, the Nature Pure QC could be a valuable "added extra". It’s not simply a carbon filter, but another kind of filter purifier which can remove particles down to 0.4 microns – and since beside mud, this includes oil based contaminates (such as pesticides) and heavy metal pollutants it’s a very useful idea for inland waterway craft.

Although it can’t be used on any briny source, it does mean that water can be taken straight out of a canal for instance – even oily water – and made drinkable. “You can take water with duck poo in it and get out something similar to bottled water,” explains Harald Charters of manufacturer General Ecology. He adds: “The bottled-water effect is because the minerals don’t get taken out along with the rest, so it actually tastes better than chlorinated tap water.”

Most of the time these units are mounted under the sink – close to point of use, via a separate drinking tap as there’s no point in wasting it on the washing up. It costs around £175 and the replacement filter (needed every 500 gallons) cost £55 – which doesn’t make it the cheapest option.

“But it means a boat can just refill straight from either the canal – or from a hosepipe from the dockside in a place like Turkey,”says Mr Charters. So, if the craft is going coastal, it might be a compromise between tanks and a full desalinating system – as long as the crew doesn’t forget and put salt water in through it!

Further it seems a lot of boatbuilders, such as Sunseeker and Fairline are now recommending putting them in line after the desalinator, as it gets rid of the distinctive "hose-pipe" taste, or fitting a basic model directly into the icemaker – as recovered water “is often truly terrible when used in ice,” adds Mr Charters.

One happy customer says fitting the unit was really easy, and “from start to finish only took around half an hour”, and now changing the filter has got much easier as well, as the latest model has uses lightweight, replaceable canisters which just turn by hand into the interface – so there’s no bother with clamps or toggles.

Tank access
There’s an element of thinking ahead with the fittings that can make life easier, or not, for the owners.

For example, tanks are needed in either case – but they can get a little unpleasant. One of the easiest things to do to help is to make sure that the interior of the tank is accessible to a physical mop out.

But even so, in order to clean it properly, boaters need to drain the tank (and if you can only use the freshwater pump it means even more cost and fiddling as it means replacing the filter). Further, after adding a weak bleach solution to help kill the residue, there’s also the need to drain, fill and drain again.

Mr Dawson recommends filtering water on the way in – just by connecting a hosepipe to a filter arrangement – although some of the new production boats are coming through with filters already placed before the sink.

Most of these tanks have to have baffles for stiffness, and these are more difficult to get around for cleaning. Mr Dawson explains that with production boats, it’s all CAD drawn, and the parts slot together. “Once in, some of the parts, including the tank areas, are difficult to get at again,” he says, although more often than not there is an inspection hatch of some kind, they are not always easy to undo. There might possibly be a case for getting an inflatable tank that you just throw away, he says, although it's not the cheap option overall.

All-in-one fit
It’s a problem that Vetus has thought about. An inspection cover, for cleaning the inside of the tank is fitted as standard to its drinking water tank systems.

Further, the company has taken steps to make it an easy fit. Stephen Baker of Vetus says that modular is the way to go, as it saves an enormous amount of time sourcing the individual parts and then trying to connect them all together.

The company has a complete freshwater tank system suitable for 12V or 24V that comes with everything prefabricated. These new water tank systems feature a high grade synthetic tank suitable for drinking water, together with an electric pump.

Mr Baker explains that the variable speed pump motor has an inbuilt sensor which regulates the water pressure and ensures a steady flow, giving a respectable output of 13.5 litres per minute at zero head.

“You don’t have the bother of putting in a conventional pressurised water system, which is a blessing,” says Mr Baker. All connections for filling, suction and ventilation are pre-fitted, together with a filter in the suction line and an ultrasonic level sensor. “You just screw it down and connect the hoses,” says Mr Baker, “The whole thing, from installation to cleaning, really has been made very easy.”

Getting clever
Whale is developing its Intelligent Control systems which mark a further shift away from a series of individual components. Firstly, the Whale IC systems offer simple, fast installation, partly because of the use of pre-wired, fully potted components, but its really the "brain" incorporated into the products which makes them interesting. At the heart of each IC system is a built-in electronic control unit which takes messages from the sensors and signals instructions to the pumps to tell them how to behave.

It makes a big difference with the performance of shower installations. Keith Nixon of Whale explains: “The typical problem with traditional freshwater systems is that high back pressure causes cycling: this means you get a reduced and often pulsating flow especially when a high back pressure outlet like a shower is being used.” The usual way to get round it is to fit an accumulator tank, which can be both bulky and costly.

Recently water system manufacturers have produced VSD (Variable Speed Drive) pumps to tackle this issue by monitoring back pressure. However, when the pump sees high back pressure, it slows the motor speed. This often sacrifices flow and generates heat inside the pump, which occasionally leads to failure.

So, the Whale Fresh IC not only monitors back pressure to prevent cycling, it also monitors voltage, system pressure and flow to completely eradicate current spikes – which amongst other things means, says Mr Nixon: “The shower benefits from the full performance of the pump with no cycling or temperature fluctuations.”

However, despite the growing sophistication of all the parts involved in onboard water systems, Mr Dawson notes that 40 years ago Sir Robin Knox-Johnston just caught water in the sails – bringing home the point that many of these items are really a luxury, and not, when all's said and done, a necessity.