How Efficient Is Your Boat's Marine Water Filter System?

Dec 12 , 2017

How Efficient Is Your Boat's Marine Water Filter System?

“Water, water everywhere, nor any drop to drink.” That famous line from “The Rime of the Ancient Mariner” by Samuel Taylor Coleridge is hyper-relevant to the seafarer, even in modern times.

The poor sailor in the 1798 lyrical poem spoke those words when he thirstily gazed out at leagues upon leagues of saltwater and realized he could drink none. Lucky for us, though, Coleridge’s problem is largely an archaic one, thanks to the help of the marine water filter.

It doesn’t matter if you’re a day sailor or a transatlantic adventurer, you know that the right marine water filter system is indispensable on board. These filters, also known as watermakers, effortlessly turn undrinkable saltwater into potable freshwater to keep you hydrated and safe on long and short journeys alike.

On-demand access to desalinated water allows you to go further for longer without weighing down your boat. It’s also a vital component for your crew and passengers’ safety.

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Before we dive into the nitty-gritty, let’s discuss the importance of an efficient, well-working marine watermaker. The most obvious reason to install one is so that you have an easy supply of fresh drinking water on deck for consumption, cleaning, and other applications.

Most large vessels opt for a built-in marine water filter over refillable tanks because they provide substantial weight savings. Rather than having to store large vessels of heavy water, built-in filtration systems instantly convert saltwater into drinking water right from the galley.

These units also eliminate the need to re-up once you get to port, and can be more affordable over the long-haul. Any distance sailor knows that on-demand water is vital when crossing oceans or making long sails between ports, and a water filtration system makes that possible.

They also reduce your risk of getting stranded without an adequate water supply since they eliminate complications commonly associated with tanks, especially leaks. But bulky, outdated, and inefficient filtration systems can put all of this on the chopping block, so you need to make sure yours is well-qualified for the job.

While the benefits of installing one of these units are clear and hard to dismiss, we can’t overstate the importance of having a backup water filter on hand. These small devices allow you to desalinate water in emergency scenarios, and should be added to your marine emergency kit right alongside your emergency radio and first-aid supplies.

You may also want to consider using a compact, lightweight water cooler on board for backup. We probably don’t have to tell you this, but the most harrowing tales of survival at sea or otherwise don’t start until the freshwater supply runs out.

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reverse osmosis illustrationAlmost all of today’s watermakers use a reverse osmosis semi-permeable membrane within the filter. The reverse osmosis method of water filtration is preferred in marine applications because it’s amazingly good at removing minute salt and larger contaminants from water.

This purification technology is also preferred in desalination applications because it has the ability to remove many types of dissolved particles, including dissolved salt. Generally, reverse osmosis systems utilize a high-pressure pump, which then pushes the water through a specialized membrane that only allows certain molecules to pass through.

Reverse osmosis technology seems like magic, but there’s actually solid science behind it. The method gets its name because the salt in the seawater naturally flows towards the water that has none. The systems apply a pressure that’s much higher than saltwater’s natural osmotic pressure, which forces only the fresh water to pass through the thin filter in a reverse manner.

As you can see from the diagram above, the membrane is able to rid the water of a wide range of contaminants. Not only can it effectively desalinate saltwater, but it can also remove microscopic contaminants such as fluoride, chlorine, lead, pesticides, nitrates, and sulfates from the water.

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Efficiency is easily one of the most important facets to a super-functional system. Depending on the type of energy it uses (more on that below), your filtration system could suck up essential energy from your ship’s generator or battery that could be better served elsewhere. An efficient system will produce more water in a shorter period of time, which means you’ll have more freshwater available to you during day-to-day activities and emergency scenarios alike.

But how do you know if your filtration system is efficient? Follow these tips.

  • Check Flow Rate — Marine water filters, like any other type of water filter, are often rated by what’s called the “flow rate.” Although all filters will slow down the rate of water flow in some capacity, better filters will eliminate that to a certain degree without compromising how much contamination is filtered.

  • Set a Timer — If your potable water filtration system is relatively new, there’s a good chance it was advertised with how many gallons of fresh water it could produce per minute. Efficient water filters will live up to their claims, so make sure to do a test based on what your unit lists as an acceptable rate of filtration.

  • Check Vital Signs — Some water filters are actually equipped with high-tech features that do all of this work for you. For example, you may find styles that have built-in flowmeters, which actually monitor how many gallons per hour are produced without you having to set a timer. Keep an eye on the flow and pressure every day.

  • Note the Operating Pressure — Another handy feature on many new and old marine water filters is a pressure gauge. Be sure to regularly check the unit’s operating pressure to make sure it’s working at its peak. Good pressure is an indicator that the unit is producing freshwater at an appropriate volume.

  • Replace the Membrane — Older filter membranes can seriously compromise your system’s ability to thoroughly and efficiently filter out particles. Check your membrane at least once a month to make sure that it’s not slowing down your unit. For more information on how to replace your water filter’s membrane, reference the maintenance section below.

  • Check the Unit’s Temperature — Unfortunately, colder and saltier water is harder to filter, which means it usually requires more energy than a standard freshwater filter. Make sure that all of the seals on the unit are tight and try to keep the unit well-insulated to prevent the filter from working extra-hard for the same result. A system that’s too cold requires more energy and will compromise efficiency.

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Water filtration systems come in a wide variety of designs, some of which are more efficient than others. Efficiency comes down to which type of energy a filter uses and also whether or not it has certain features that make it work faster and smarter.

One of the most common myths in the yachting community is that these types of filters are energy hogs. While that may have been the case 20 years ago, new advancements help mariners produce more potable water while still drawing less energy.

  • Engine-Driven — Unless you’re a dedicated row-boater or kayaker, there’s a good chance your boat has an engine, even if your vessel is powered by the wind 90 percent of the time. Powerboats can almost always benefit from an engine-driven system because the motor will be running anyways, which means less extra power consumption. These units are installed inside the engine compartment and draw power whenever your engine is running.

  • Towed, Water-Powered — You’re surrounded by water, so why not take advantage of it? Portable, towed watermakers such as the Waterlog Watermaker brought some big promise for boaters about a decade ago because they didn’t require any electricity or fuel to power. But it seems that, like most things in life, these units were too good to be true.

Boaters claimed that the units worked poorly and sometimes didn’t produce even enough water for a single cup. For now, it’s best to use a system powered by electricity or gas.

  • Generator-Powered — Besides engine-driven styles, 120V AV watermakers are the most popular on the market. These styles are run from an auxiliary generator or an inverter with other AC loads and typically use lower pressure designs to make the units run more efficiently.

Some people recommend using a high-pressure pump off the generator in order to increase pressure without compromising too much efficiency. One thing to note about this type of filter is that they sometimes have energy recovery systems built-in, which can reduce power consumption. Unfortunately, these units are typically much more expensive.

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Another important factor to maximizing your water filter’s efficiency is to perform some periodic maintenance. Like almost any kind of water filter, your watermaker will work best when the filters are in good shape.

Reverse osmosis water filters rely on their membrane, but these membranes can occasionally thin or become clogged. Other parts and components should be regularly checked, cleaned, and replaced for the best possible performance.

  • Replacing Filters – As previously mentioned, one of the simplest things you can do to ensure that your water filter is performing at its peak is to replace the membrane, which you can do by upgrading to a new filter. How do you know when it’s time to replace your filter? Make sure to check the pressure gauge daily. If you’re clearly losing pressure, then it’s time to buy new marine water filters for your boat.

  • Keep it Wet — Besides swapping out the membrane, the next most-important facet of keeping your watermaker in good working order is to ensure that the membranes are always wet and healthy. If you talk to any savvy seafarer, he or she will tell you that this means running your filtration system at least once a week, even in the off-season.

When your membranes are properly hydrated, they’ll resist drying out and will remain their best shape for the long-term. Drying out your watermaker will drastically reduce its lifespan.

  • Check Certain Components — Like any piece of equipment, your watermaker is only as efficient as its smallest part. Make sure that you regularly change the crankcase oil on your high-pressure pump at least every 500 hours of usage and after the first 50 hours when it’s first installed. This will help keep the components properly lubricated so they don’t dry out or cause damage due to friction.

Also, be sure to regularly clean the salinity probe (the component that measures how much salt is in your saltwater) so you always get an accurate reading.

  • Test, Test, and Test Again — After you’ve performed any sort of watermaker maintenance, make sure that you do a complete check on the unit and measure the salinity of your water, the pressure and how much water it’s producing per hour. You should also visually inspect all of the components with the unit running so that you can be sure there are no leaks or components slowing down the flow.

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The great thing about a high-quality reverse osmosis boat filter system is that it can be easily maintained with affordable replacement parts and filters. But, as you’ve already learned, these units can be quite temperamental. If you’ve completed all the maintenance steps above and have replaced your watermaker’s filter with no measurable change in water output or pressure flow, then it may be time to replace your unit altogether.