ALL ABOUT WATERMAKERS
Water, water, everywhere, nor any drop to drink. So I called for some water-divining intervention and, at that precise moment, the imaginary metal rods in my hand began spinning uncontrollably before suddenly pointing like a duck-hunter’s dog to the bottomless source below.
Yep, after years of dreaming about it, I now have a watermaker on our Riviera 42ft coastal cruiser. And with that a whole new world of possibilities opens up this summer. Should we cruise north or south, have a boatload of freeloaders aboard, should the crew demand its umpteenth deck shower after as many dips off the duckboard, no worries, I have water to spare.
But I’m not alone with my newfound ability to top up the water tanks at the press of a button or two. Thanks to tough water restrictions in summers past, more and more Australian boaties have been fitting watermakers to top up their tanks and keep their decks clean. Which is to say nothing of the $1.9 billion desalination plant now being built at Kurnell, which uses similar technology to our onboard desal’ plants.
Although far from small change, splashing out on a watermaker will change your boating life forever. It takes you from camping on board to a state of total self-sufficiency —
and real luxury. You mightn’t realise it over a weekend, but during a week, or a longer sabbatical like that during the present holiday season, your cruising options are virtually limitless without compromising your ship’s comfort level.
But there are other benefits from fitting a watermaker. Because you no longer need to head away with full water tanks, you save on weight and, thus, fuel. Remember: a litre of water weighs one kilo. Carry 400 to 600lt of the lifeblood and you will soon notice it as you set sail.
Given that the average Australian uses about 300lt of water per day —
the average domestic consumption for our present family of three is 475lt a day — we have a thirst for water. And this is without our crew taking deck showers after diving off the duckboard every few hours. But once you throw an extended family aboard your boat, water evaporates fast. With a bunch of kids running riot, your entire onboard supply can vanish in the space of an unsupervised Sunday. Believe me.
OUR WATER USE
For the record, our 42-footer has twin interconnected polypropylene water tanks in the engineroom that collectively carry 450lt. This modest water supply services two freshwater flush toilets, three showers including the deck model, a dishwasher, washing machine and icemaker. Okay, so we’re hardly roughing it.
With all the abovementioned amenities, and with due diligence and water-conservation measures, we can last a week aboard at somewhere like Jervis Bay using just half a tank. This requires using a bucket as a loo, rinsing plates in saltwater, brushing teeth with a glass of water, taking nun’s baths and one deck shower per crewmate per day.
I’m betting hardcore sailors are now scoffing at our apparently profligate use of water. After all, you only need about 2lt a day to survive. And as Trade-a-Boat’s yachting crew, Allan Whiting, will attest, you can get around taking showers or flushing a freshwater head. Similarly, if you are living aboard and on the move, you might only need a low-volume, continuous watermaker to top up your tanks.
But not for us. Like most readers, our charter is pleasureboating and there is immeasurable pleasure to be had aboard a boat with all the mod cons, not least being the long hot shower at the end of the day that takes you from crusty to toasty when you tuck under your crisp sheets. And when you are hitting the beach as often as we do, it’s a boon to be able to rinse off before heading inside.
Furthermore, freshwater rather than saltwater toilets don’t smell when left idle and, with a young child in tow, we use our onboard washing machine and dishwasher. As a bonus, watermakers make spot-free water. Add a water blaster with a long wand —
as I have just done — and you can hang up the chamois and save on detailing. At least that has been my thinking.
HOW THEY WORK
Watermakers, including the huge Kurnell one, use a process called reverse osmosis. Seawater is pumped under pressure through a membrane that removes 98 per cent of salt, minerals, bacteria and other contaminants. Under ideal conditions (25-degrees Celcius water temperature), it is possible to get an 18 to 20 per cent return from clean seawater. The remaining 80 per cent of concentrated brine is returned to the sea.
There are mechanical watermakers that you can tow behind a boat and other handheld survival models that can make a few litres after manual pumping, but most marine models rely on electricity to make from 30 litres to 300 litres per hour of operation. High-capacity watermakers achieve their output by employing a high-pressure 240V pump. So you will need to run a generator if you want a fast return. But there are also 12V and 24V models better suited to yachts and long-distance expedition boats where an engine(s) and battery charger might be running 24/7.
MODULAR & GENERATOR
Although watermakers aren’t usually compact, the advent of modular models in recent years means that you can now fit a high-capacity model in a small engineroom. This I did, settling on an American-made Horizon Reverse Osmosis (HRO) modular model called the Seafari SFM 700-1 for, among other reasons including pick-up-the-phone troubleshooting and service, it’s high output of 110lt/h off the back of our 9kW Onan generator.
Should I choose to spend a few thousand more I can retrofit a second desal’ membrane cartridge to the unit and double output capacity to 220lt/h. Maybe next year. But do shop around, as there are more and more desalinators on the market these days and prices vary quite widely. In my case, I tend to spend a premium for a top product in the expectation of not only superlative performance but also aftermarket service.
Meantime, in just two hours of generator operation —
say after breakfast when the family is ashore or in the afternoon while I’m recharging the house batteries and firing up the (240V) barbecue — I can make half my boat’s water capacity.
Remember: high-pressure watermakers like ours are noisy and, thus, best operated when you are outdoors or stretching your legs ashore.
It’s a small price to pay.
The installation took two crack crew from Riviera’s R-Desalination division one-and-a-half days while my boat was tied to the marina. For the intake, we borrowed the existing seacock for the boat’s raw-water deckwash. A few days later, when the boat was slipped for its annual antifouling and Prop Speed, a new seacock was tapped and the deckwash reconnected. (The skin fitting for the brine discharge, perhaps shown in a photo hereabouts, was also refitted in a cleaner manner, with a Silastic or Sikaflex wipe).
Surprisingly, at least at first, the reverse-osmosis system comprises relatively few parts, with the fiddly bit being the running of the high-pressure plumbing lines and wiring. Before striking a blow, you need to look about your chosen mounting space, be it the engineroom, lazarette, or some other storage void, and measure up.
Access is also crucial. While I need only flick a switch in the galley to operate our watermaker, I need to enter the engineroom at each new location and perhaps even during each new tide to adjust the unit’s output at the main membrane. This is because desalinator’s output varies depending on raw water quality, its temperature and salinity as well. To maximise filet life, you don’t want to be forcing more water through the membrane than its rating.
For this reason, the pressure adjustment controlled alongside the main membrane is mounted where it’s easily accessible. If you plan on fitting your own desal’ unit, something you can do without voiding warranty, give due consideration to servicing access and plan carefully.
BEGINNING TO END
Logically, the installers start from the beginning of the system, the raw-water intake, and work towards the end, the product line feeding the starboardside polypropylene watertank, which is connected to the portside tank for balance and to ensure a complete fill.
The saltwater for the watermaker enters via a through-hull fitting with ball valve. While you might have to slip the boat to have a through-hull fitting tapped, as mentioned, we used the existing fitting for the saltwater deckwash fitting instead.
The seawater is filtered for large debris through a sea strainer, which was mounted aft of the engines near the engineroom hatch so I can access it. Suffice it to say, sea strainers get clogged with weed — especially in places like Myall Lake, where a watermaker will be a godsend —
which is why the clear glass-cylinder types are preferred over the solid sealed units as they permit at-a-glance inspection.
The first of two 240V pumps fitted outboard of the starboard engines is called the booster pump. It takes the water to 30psi and draws it through the said through-hull fitting and sea strainer to a brace of separate 25 and 5 micron pre-filters. These filters were mounted on the rear bulkhead in the engineroom for access. The elements will need to be changed a few times a year.
There are inlet and outlet pressure gauges on the brace of pre-filters (the ones with a blue canister) whose needles read roughly the same to indicate a free flow of water. If there’s a disparity the filters need cleaning or replacing. The HRO system includes low and high-pressure sensors warning of as much as well.
After sediment and suspended solids are removed, the feed water enters the second pump, a high-pressure pump and, at 700 to 800psi, it’s driven through the semi-permeable reverse-osmosis membrane. A back-pressure regulator automatically maintains the correct pressure. Both low and high-pressure switches automatically shut down the watermaker in the event of incorrect flows.
Freshwater now flows from the membrane through a flow meter where the amount of potable water and brine produced per hour are registered. There are knobs to adjust here so that I am making the optimum amount of potable water, as in this case, 110lt/h with the Seafari SFM 700-1 model.
A salinity probe ascertains the salt content of the water. If the water is good quality, it passes through a charcoal filter, which purifies it of unpleasant odours and taste, before it drops into my tank. If it’s not good water it’s diverted overboard.
The product water quality is reflected by as little as two green lights or as many as five or six green lights on an illuminated water-quality sight gauge on the main control panel. Dodgy water is orange and if you see red then the system isn’t working.
Importantly, I can see the water-quality lights from the cockpit, when I duck and look through the engine hatch, down the centre of the engines, to the forward bulkhead where the main element and control panel are mounted. Thus, at a glance, I can confirm the water is good quality. There’s also a green light on the on-off touch pad in the galley.
ON THE WATER LEVEL
Even given the above explanation, one really doesn’t need to immerse themselves in the processes involved. Hit a button in the galley, tweak a knob, cast a cursory glance at some lights, and we are now making water. Hit the stop button and the automatic backwash function runs for about 10 minutes. This is important!
Reverse osmosis watermakers or desalinators needs to be used often and flushed often to keep their membranes clean. If you are an infrequent boat user, it is best you top up your tanks from the marina and ration. There is no substitute for regular use, which, it should also be said, results in ongoing filter use. I am now carrying a complete filter replacement kit. Life without endless water isn’t worth entertaining.
The general rule with watermakers is that to make good water you need good water. Some use a four-to-five metre rule, that is, you need to see the bottom in that depth to make water. Obviously, a lot of suspended particles means clogged pre-filters. These filters can be hosed out to a point.
But it’s best to head to sea or an oceanic anchorage or a clear-water environment to make water (mid-passage makes sense). If that means we have to cruise to a beach and down anchor to fill our tanks that’s a small price to pay. Not so the HRO watermaker, which costs about $15,000 installed. But what price endless water?
Meanwhile, when left on shorepower, the Seafari SFM 700-1 with automatic backwash function flushes itself once a week to prevent spoiling of the membrane before our next big voyage. Like most things in life, there are servicing requirements of the pumps and the filters have a life expectancy.
But we no longer need to run back to the yacht club or marina to top up the tanks or wash the boat. Or ration in remote locales. Expert forecasters are predicting a long, hot, dry summer. “Press the button, honey.” Ahhh. By the way, the ‘soft’ water does wonderful things to your locks, offers a spot-free rinse of the decks (high-pressure pump and wand also installed), and it tastes pure and great. Now I’ll drink to that.
Photos: A flotilla of luxury cruising cruisers seeks refuge off Mrs Watsons Bay at Lizard Island. You won’t last long at The Great Barrier Reef without a watermaker; The Horizon Reverse Osmosis watermakers are available as modular models for ease of installation. This is the author’s HRO Seafari SFM 700-1 before taking up residence aboard his 42-footer.