Water Purification Onboard


Water Purification Onboard. In the first article on water onboard we looked at watermakers. Now you have made good clean drinking water with your watermaker it will all go for naught if the rest of your system is not up to par. Bacteria can grow in water that is sitting idle in your water tanks.

This article looks at water purification onboard. water comes from a variety of sources. We look at how to keep your water fresh and safe whether its from your watermaker, water brought in from shore, water sitting in your water tanks and then the water system between the storage tanks and the faucet. Systems for clean water onboard include;

  • Filter water as it comes aboard
  • Keep tanks and pipes clean
  • Filter water after tank & before point of use

How to Treat onboard water

  1. Water from your watermaker
  2. Dock water
  3. Water storage tanks
  4. Supply side of the water tank


1 Water from your watermaker (soft water)

The water you have just produced from your watermaker probably has a low PH and it is soft water. Water with a low PH is acidic which is not good for metal water tanks. PH is a measure of the acidity of the water and hardness is a measure of calcium content.

PH levels

PH levels are recommended to be in the 6.5-9.0 range. PH regulations are to minimize corrosion of piping materials so that metals, do not dissolve into the drinking water supply. If your PH level is below 7, you can consider putting a PH increaser filter as a final stage of your reverse osmosis system and correct acid water problem easily.

Water Hardness

Hardness of the water is generally expressed in parts per million ppm. Soft water has less than 125 ppm, hard water has greater than 200ppm content.

Increasing PH of product water

If you need to raise the product waters PH level, which also will make it harder you can run the water through a neutralizing filter, before it goes into the boats water tanks.



Whole House Acid Neutralizing Water Filters contain naturally occurring, crushed and screened white marble, calcium carbonate media. It is used to neutralize acidic or low pH waters to a neutral, less corrosive effluent.

Acidic water can leach unhealthy levels of copper from pipes and cause greenish-blue stains on fixtures. It can cause many other corrosion problems as well and drastically shorten the life of all water using equipment, including dishwashers, washing machines, hot water heaters as well as fixtures.

2 Dock water (hard water)

Your main source of water is the water you fill up the tanks with at the dock. Dock water provides a different issue than watermaker water as it is hard water. Hard water contains a high solution of calcium and magnesium salts. It will also cause white stains when cleaning the decks. Soft water, on the other side, does not contain these salts.

water softeners; To soften hard water there are several filter solutions.

Spot Free Water Filter and Softener System

Spot Free
Spot Free

The Spot Free portable water filter and water softener system removes chlorine, ammonia, and hard water minerals – such as iron, calcium, magnesium – for use on all vehicles, in the home and for improving drinking water. Spot Free will provide a virtually spot free wash down on vehicles, but more importantly, will extend the life of plumbing, fixtures, water heater elements, icemakers, etc., on boats and RVs.

The Spot Free water filter and water softener system has been tested and proven by the International Yacht Industry. Designed explicitly for the treatment of POTABLE WATER, using the system to fill the tanks of a boat or RV saves time and money on costly maintenance.


water conditioning
water conditioning

SmallSpacesAppliances.com provides Appliances, Compact Kitchen Appliances, Refrigerators, Grills, Microwave Ovens, Electric Cooktops, Coffee Makers, Water Softeners, Reverse Osmosis and LED Lighting and LED Light bulbs for people living in Small Spaces like Yachts, RVs and small apartments.

Small Spaces provides the E Series compact Built-in water softeners for water conditioning on boats, yachts, RVs, Luxury Yachts, Motor Coaches.


3 Water Storage

Treatment of water in the tank (keep out bacteria and organisms)

Compared to your house domestic water system, a boats water supply is sitting in a water tank for relatively long periods. For this reason some precautions are worthwhile.

Aqua Clean
Aqua Clean

Aqua Clean

Starbrite’s Description

Water conditioner to keep water fresh

Features: Cleans and deodorizes fresh water holding tanks and supply systems Excellent for use after storage or winterization Flushes out scale and sediment Use periodically to prevent foul taste and odors One gallon of Aqua Clean treats 100 gallons of water Remarks: Safe and effective product. MSDS Info:



Tank water can be treated with special disinfectants, often containing very low amounts of active chlorine. Add small amount of unscented chlorine bleach to each tank prior to filling. Just enough that there is a faint trace of chlorine when you run the water.

20ml of Hadex will treat 1000 liter of water. This will impede growth of bacteria, algae and other micro organisms in the water, and should be added at least once a month.

There are also products which do not contain chlorine, but silver such as Katadyn Micropur, Micropur Classic inactivates bacteria in water tanks and containers. It is ecologically friendly and keeps water free from germs, algae and odors. Silver ions preserve water for up to 6 months.


4 Water Polishing (keeping tank water clean)

3M model
3M model

3M model

Passagemaker magazine had a good article in their May/June edition of the fine magazine. The article was called “Water Polishing”. The concept of the article is similar to Fuel polishing systems.

3M model WV-B3 filter. A separate set of water hoses and a high flow pump take water from the tank and pass it through the pump and a filtration system and then back to the tank. This filtration is carried out on a timed basis, so water is continually being cleaned. This way you are not relying on the filters that are at point of use i.e. in the supply line just before use. You can maintain clean tanks and water.


Supply side of the water system

Treating water Between the water tank and the point of use i.e. the faucet.

Carbon Filters (reducing chlorine taste).

Aqua Filta
Aqua Filta

Carbon filters remove 60-90% of chlorine form the water. Shore side or Dock side water contains chlorine to stop _bacteria, algae, and micro organisms. You also added chlorine to help preserve the water in your water tanks. Removing this before use will help the taste of the water.

Jabsco the Aqua Filta Activated carbon filter

There are many different kinds of carbon filters. Most carbon filters are combined with a built-in particle filter (between 20 micron, to 0,5 micron).

Jabsco’s Description Aqua FiltaTM is an activated carbon water filter that removes chlorine, unpleasant smells, tastes and colors from marine water systems and uses specially silver-impregnated carbon to inhibit bacterial growth in the filter bed. Aqua FiltaTM absorbs dissolved impurities but retains beneficial mineral salts, thus freshening and cleansing water to make it natural tasting, sweet smelling and crystal clear.



SEAGULL IV DRINKING WATER SYSTEMS. Tired of the expense and hassle of bottled water… Want great tasting water straight from your kitchen sink? Seagull IV drinking water systems cleanse water instantly and effectively without chemicals, hold-time, or electricity!!

General Ecology drinking water systems utilize our proprietary “Structured Matrix” technology for chemical-free cleansing to provide great tasting and refreshing drinking water. Relied on by customers for over 30 years and in over 40 countries world-wide.

Ultraviolet water sterilizers
Ultraviolet water sterilizers

UV light Filters (remove organisms)

Wiki definition

UV is often the last device in a treatment train. UV radiation affects microorganisms by altering the DNA in the cells and impeding reproduction. UV treatment does not remove organisms from the water, it merely inactivates them. The effectiveness of this process is related to exposure time and lamp intensity.

There is no residual disinfection in the water to inactivate bacteria that may survive or may be introduced after the water passes by the light source, which means that the UV unit should be located as close as possible to the point-of-use since any part of the plumbing system could be contaminated with bacteria.

All the products above are just a sample of what is out there. The article shows you how and what kind of products you need to keep your drinking water safe.