Fresh water filtration - is it safe?

Mar 5, 2021
1
Beneteau 2008 Oceanis 46 Newport
I've been told by many that drinking water directly from the fresh water tank isn't a great idea unless it's first boiled.
So I am looking into a filtration system to add at the galley sink. Curious to know opinions on (1) whether it's safe to drink, and (2) which systems have been used successfully.

Thanks!
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
I just did this. Practical Sailor has done a 3 part series on how to get to safe, clean drinking water onboard.

Long story short. I've gone to an inline 10" Pentek - 155162-43 CBC-10 Carbon Block Filter Cartridge.
 
Sep 25, 2008
7,075
Alden 50 Sarasota, Florida
This is one of those “right tool for the job” actions. Carbon filters are effective at removing odor and taste from some chemicals but not for many bacteria and virus pathogens which means they are good at what they do but provide a false sense of security when it comes to other contaminants.

We don’t drink the tank water.
 
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Mar 26, 2011
3,399
Corsair F-24 MK I Deale, MD
The short version of the PS article is that it suggests a multi-layered approach. As Don says, a granular carbon filter alone will provide a false sense of security.
  • Clean and sanitize the tank annually or as needed (ANSI procedure)
  • Pre-filter the water to remove fine solids (not a carbon filter--you want to leave the chlorine in at this point). The main purpose is to keep the tank moderately clean to reduce the potential for solids accumulation that the chlorine cannot penetrate. Also, there can just be a lot of crap in pipes and hoses. 1-5 microns.
  • Chlorinate. Perhaps not needed if the city water is good and chlorinated. You can test for chlorine residual with aquarium kits. This will kill the bacteria and deactivate viruses.
  • Filter to remove cysts (giardia etc). The chlorine got the viruses and bacteria, but cysts can resist low levels of chlorine. The recommended carbon block filters are NSF rated to remove cysts (typically 0.5 micron), most bacteria, and chlorine.
At this point, yeah, it's probably better than most tap water and bottled water.
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
Yeah my bad for only mentioning the last of 3 parts. "Long story short. ....".
The complete process involves cleaning the tank and filtering incoming water. I've always used a dedicated hose and filter on the dock supply. I recently, as part or this water filtering process, installed an 8" inspection plate on the top of my tank so I can scrub it out before bringing the system online.
Before next haulout I plan to complete the supply line bypass so I don't have to add the pink stuff into my tank anymore
 

leo310

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Dec 15, 2006
635
Catalina 310 44 Campbell River BC
This is what we have installed and used over the last 4 years with no problems.
  • Rainfresh Drinking Water System 2 is a high performance under sink water filtration system provides safe, premium quality drinking water
  • For use at home, cottage/cabin, farm, business, boat or RV - effective on both treated municipal water and untreated well, lake or river water
  • 3-stage filter system - 5 micron (nominal) activated carbon block cartridge (62-1038) and 0.3 micron (absolute) cleanable, reusable ceramic cartridge (62-1002) with activated carbon core
 
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Likes: Tom J
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
We've used one of these filters for years and reserve it for drinking water only. Otherwise, no problem here with drinking water straight from our tanks. Always tastes and smells clean. Refuse to spend money on bottled water when we have the best drinking water around.

 
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Jul 7, 2004
8,402
Hunter 30T Cheney, KS
For the ultimate test. Once online, I may take a water sample from the boat and one from our home's RO system and have them checked for purity
 
Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
have an inline filter originally used on aircraft installed in the line from tank to sink. I periodically clean t he tanks with a large slug of Clorox, flush them,, pump dry and fill with fresh. And figure it's silly to carry water around and not be able to drink it.
Lived aboard my previous boat for over 4 years and cruised full time on this one for over 2 1/2 years- no problems. :D

Cannot imagine havbing 30-40 gallons of tankage and not keeping it drinkable
 

capta

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Jun 4, 2009
4,766
Pearson 530 Admiralty Bay, Bequia SVG
I've been drinking water out of the water tanks on vessels of all sorts for around 6 decades with no apparent ill effects.
On my own boat, that's all I've ever used; I do not do bottled water unless there is nothing else available when ashore. Mostly we drink tap water ashore when it is potable.
If you are worried, wash out your water tanks and make sure you fill them with potable water. Of course, a water maker solves all those problems. As above, a carbon block filter, mostly for taste, can be installed on a separate faucet for drinking water only, if you wish.
 
Sep 25, 2008
7,075
Alden 50 Sarasota, Florida
For the ultimate test. Once online, I may take a water sample from the boat and one from our home's RO system and have them checked for purity
Be careful what you ask for. Purity can be defined many ways. And testing for chlorinated hydrocarbons, some heavy metals and pathogens can be very expensive and like a Covid test, the results are valid only at a discrete point in time, not predictive.
 
Jul 12, 2011
1,165
Leopard 40 Jupiter, Florida
I follow the instructions for refeshing tanks with liquid chlorine, as published by @Peggie Hall HeadMistress 's book, practical sailor (Decontaminating a Tainted Water Tank - Practical Sailor), etc. conforming to guidance developed for RV's (ANSI A119.2 section 10.8). I see no difference between water in a polyethylene jug on the shelf for a few weeks and 20+ gallons in a clean polyethylene tank built into the boat. We pre-filter before filling with one of those in-line hose filters for RVs (about $25 for a few thousand gallons filtering)

If you do use a filter anywhere (pre-filters, under-sink filters, etc.) be religious about changing them at the manufacturer's recommendation (or before, if you're just estimating). Those filters become breeding grounds for all sorts of really nasty bacteria. You're worse off with an old filter than just fresh municipal water.
 
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CarlN

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Jan 4, 2009
603
Ketch 55 Bristol, RI
It's absolutely feasible to have safer and better tasting water from your tanks than ashore. I ban bottled water from my boat for the environmental foolishness of trucking plastic bottles all over the world. My back also appreciates not having to lug cases of the damn stuff aboard. Some of my regular guests say they look forward to coming on my boat because it's the best tasting water they know.

One thing that people get wrong is using too much chlorine. Once the tank has been cleaned well, it takes very little chlorine to keep it that way. 2 teaspoons of household bleach will protect 100 gallons without chlorine odor if the water is from a watermaker or a marina hose. Get the pool test strips and check the water from your faucet. 1ppm chlorine is about right for drinking water (pools have 3ppm - you can smell it). You really can barely taste 1ppm chlorine but if you then run it through a final filter it will taste wonderful. After adding chlorine wait an hour before measuring.

Note also that chlorine in a vented tank (like a boat tank) will evaporate within 48 hours and the test strip will show no chlorine. That's OK if it doesn't sit that way for more than a week before the next fill. And if you fill your tank at a marina, the easiest way to keep your tank clean is to completely empty it before filling. This will get any water that was starting to go bad off the boat and the new chlorinated water will kill anything remaining.
 

Tom J

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Sep 30, 2008
2,301
Catalina 310 Quincy, MA
I use an inline filter when filling the water tank. It's amazing what flushes out of that filter when I back flush it. Some of the water lines on docks sit unused in the sun for days, and are breeding all kinds of stuff.
In addition to cleaning the tank periodically, I use a two stage water filter under the galley, with a dedicated faucet for drinking. Here in Hawaii, we collect rainwater in a 15,000 gallon tank and filter it with a three stage filter for all household needs. Some of the unfiltered water is diverted for irrigation.
Someday I'd like to get a watermaker, since keeping enough fresh water on board can limit how long we can anchor out.
 
Jan 22, 2008
79
Gulf 29 Little Current, ON
We treat the tank and lines with Purogene (2% chlorine dioxide) at the beginning of the season. It can also be used in small amounts during the season.
All the water that we use for cooking/consumption goes through a Aquagear water filter pitcher:
"Removes 20x more contaminants than leading competitor, including fluoride, lead, chromium 6, chloramines, mercury, and chlorine. The filter keeps healthy trace minerals like calcium and magnesium in your water, which other filters will strip out."
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
This is a good Potable Water link, in which a lot of SBO people chimed in.
This includes Drinking Waters Standards too.

carbon filter for the water

Do not the title fool you.
Jim...

PS: MaineSail has the best system!
 
Jan 1, 2006
7,039
Slickcraft 26 Sailfish
We treat the tank and lines with Purogene (2% chlorine dioxide) at the beginning of the season. It can also be used in small amounts during the season...
"Removes 20x more contaminants than leading competitor, including fluoride, lead, chromium 6, chloramines, mercury, and chlorine. The filter keeps healthy trace minerals like calcium and magnesium in your water, which other filters will strip out."
Chlorine dioxide is a strong oxidizer and can kill all pathogens. It oxidizes contaminates."
It's a stretch to understand how this filter knows the difference between heathy trace minerals and unhealthy minerals. I guess it's pretty smart.
 
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
Welcome to the forum!!

Whenever I purchase a used boat I always flush the fresh water tanks, treat with chlorine and flush. After that no problem. We only use water from the fresh water tanks for coffee, cooking, brushing our teeth, washing our hands, washing dishes and showering.
 
Mar 26, 2011
3,399
Corsair F-24 MK I Deale, MD
Chlorine dioxide is a strong oxidizer and can kill all pathogens. It oxidizes contaminates."
It's a stretch to understand how this filter knows the difference between heathy trace minerals and unhealthy minerals. I guess it's pretty smart.
Advertising copy. Calcium and magnesium are not trace minerals. "Leading competitor" is meaning less, if you pick some minimal filter that people buy. And any carbon filter will exhibit this same discrimination, to a variable extent depending on design and doping. Carbon block filters are particularly effective. That said. someone above mentioned ceramic filters (Daulton makes some very good ones) which are well proven against microorganisms.