Filtration/purifying, upstream the watertanks

Watermaker (Sea Water Reverse Osmoses)

Well known filtering in the nautical industry is done by a watermaker, upstream the watertanks. Watermakers that purify salt water into fresh water, via reverse osmoses, is the most thorough way of (membrane)filtering. It removes all possible dirt, metals, bacterias, chemicals, pesticides etc. A perfect source of water for cleaning (since it doesn’t leave calcium stains).  However, Sea Water Reverse Osmosis tends to bring the pH value of the treated water below its neutral level of 7pH, making the water acidic and therefore aggressive towards the yachts plumbing system, aggressive towards your skin while enjoying a shower and not particularly healthy when used as drinking water. A very simple solution regarding the first two issues is to equip the yacht with a pH neutralizer in form of a lime stone filter. In regard of drinking, your water maker is only one source of many which fills up your fresh water tank and requires further considerations.

Filtration/purifying, downstream the watertanks

The available water source to be treated on a yacht is in general a mixture of RO treated sea water and/or various shore based water sources which can bring a variety of chemical and pathogenic (bacteria, virus, algea etc) contamination with them. Once stored in your fresh water tank this source is further subject to pathogenic growth (mixed at favorable temperatures) and possible chemical contamination leaking from your piping or tank (copper, aluminum, non food grade plastics etc).

Treatment solutions at different levels:

Level 1: Fine particle filtration / Level 2: Micro filtration

Fine particle filtration and micro filtration can be considered as a pre-treatment to remove particles like sediment, algae and large bacteria. We don’t consider it as a complete filtration process on yachts.

Level 3: Ultra filtration (UF) or Ultra violet (UV)

To overcome the risks of pathogenic (bacteria, virus, algae etc.) contamination Ultra filtration (UF) in combination with an Activated Carbon filter is sufficient. This treatment solution doesn’t require electrical power, doesn’t use any chemicals and doesn’t reject water and can be installed under your sink without efforts nor doesn’t require a lot of space.

Another solution on this treatment level is the combination of an UV-Filter (sterilizer) with Activated carbon. Similar sizes, though electrical power is needed.

While the UF or the UV filters respectively sterilize the pathogens, the activated carbon ensures the elimination of odor and taste.

Both options require attention regarding cartridge replacements according to the diverse water sources and particular when they are not permanently in use.

Level 4: Nano filtration/Level 5: low pressure reverse osmoses (Low RO)

To eliminate also chemical contamination such as heavy metals, pesticides, micro plastics and pharmaceutical residues a higher level of treatment is needed. For this, nano filtration or low pressure RO are appropriate. Not only for yachts operating in sea water which use watermaker treated seawater as well as shore based water sources as raw water source, but also for yachts operating in fresh water (lakes and rivers) can use these filtration systems as raw water input for the filtering/purifying into superior quality of drinking water.

Nano filtration is based on the same physical principals as RO though limited to a molecular cut off weight of 100-200 Daltons. Commonly found contamination below that weight is based on aquatic salts and doesn’t exist in your shore based water source or has been treated by your water maker. Nano filtration requires less electrical power and rejects less water (around 35 %) than low RO (40-50 %).

Complete solutions come in general in three stages based on pre-filtration (micro filtration and activated carbon adsorbtion), purification (Nano, ROlow) and post-filtration (re-mineralization). Under-sink purifying/filtration units producing around 50L/h are sufficient to provide a yachts crew, owners and guests with drinking water in a superior quality compared to bottled water while having a minimal environmental footprint. The more advanced solutions on this treatment level are equipped with sensors which monitor the waters quality and communicate the technical status of the unit regarding maintenance intervals. An important added value to be always sure about the right waterquality.


If you are interested to know more about one of the mentioned filtration/purifying systems or to receive a customized proposal for your yacht, please get in touch (contactform at the bottom of this page) or if you haven’t completed the Survey Turn the tide on plastic complete this one first, to enable us to advice you correctly.

For the further distribution (via multifunctional taps or dispenser), cooling and carbonization of the filtered/purified water, please surf to the next step in the action plan: Cooling/carbonizing