How long is it safe to leave fresh water in tank?

[Shaneesprit]

Try and look up videos from “Milin Patel Water Hydrate the imagination” For everything you want and didn’t want to know about drinking water.

[Andrew Lippman]

I would be careful using chlorine in a water system with a watermaker. I think the chlorine will damage the watermaker when you back flush it.

[cdcorl]

We only use water from our water maker and have never had a problem. A couple years ago I accidentally left a tank full when we were on the hard for 5 months. No issues at all. During the season we fill the tanks every 2 weeks, and always switch between tanks.

[jlubinsky]

Consider the tank material. Nylon/ plastic grows junk better than most metals. A lab technician who knows about this told me that my nylon/ Non-metal tank makes a good culture growing surface. Had to remove the tank, fill with water and concentrated bleach, let soak and slosh it around to get it clean. The translucent material allowed me to see the growth inside ie. Dark patches.



I believe that the growth matter was originally sourced the marina dock hose where boaters performed pump out and often mistakenly used the wrong hose to rinse out the extra residual in their tank.



My advice, like i others, be careful of the source of the water and the tank material and hoses inside your boat...


Don't go overboard like my friend thinking more is better and poured a gallon of swimming pool chlorine into his tank. Took several drain and refills to clear that chlorine out of the system. The chlorine to water ratio he used was 100Xs what I use in my 20,000 gallon pool.

[cottonsail]

We use an "American Scientific" water filter. It was recommended by Practical Sailor some years ago. Great water aboard.

[Nicholson58]

We have 4 water tanks, 280 gallons total. We leave them full in Trinidad for the six months of hurricane season. It’s not been an issue except for an occasional red-brown algae bloom. That makes the agitated water cloudy but no taste.

[Peeew]

I use mainly RO water from my Watermaker. Once a year or so I do send some bleach through the whole system just to prevent problems since I do occasionally add city water when at my home dock. I did add a carbon filter to my cold tap in the galley. I use this for all my cooking and drinking water. Additionally I do carry a simple backpackers gravity feed water filter system in case I do get contaminated. These filters are very effective and cheap. I have filtered the dirtiest creek water you can imagine while hiking and never got sick.

[David WYG]

I have a 200 gallon in keel fiberglass tank. We liveaboard so have regular water flow through dock water. I routinely use untreated water from the tank that has been sitting for six months when we travel or have dock water issues. I don't let it sit longer than that. If I still have water in it after six months I run it empty and refill. Your storage time will vary depending on what material tank you have, where the tank is located, whether or not it is treated, and how warm the water gets. Our boat is usually in South Carolina or Florida, but the tank is located about three feet under water with no light infiltration, so it stays much cooler than tanks that are in a compartment. Translucent plastic tanks above the floor in say an engine room won't stay fresh nearly as long as fiberglass tanks below the floor in a cool, dark place. So, the answer to your question is - it all depends. What type tank do you have and where is it located? Obviously, if you have any odor or bad taste coming from the water after you run the faucet for a bit you should empty and refill. Remember that the water in lines will go bad much quicker than water in the tank, so a smell when you first turn a faucet on will indicate the water quality in the lines, not necessarily in the tanks.

[garyfdl]

Originally Posted by JPA Cate

Someone above questioned that US waters were slowly becoming more jeopardized. Here's a link to an EPA report: https://www.epa.gov/report-environment/water It is only one of the references under Simi 60's link.

That someone was me, and here's what 'your'/Simi's report says about US drinking water systems:

• "Of the population served by CWS (Community Water Systems) nationally, the percentage served by systems for which no health-based violations were reported for the entire year increased overall from 79 percent in 1993 to 92 percent in FY 2021"

So in other words, it's getting better. And just as a point of reference? About 87% of all Americans get water from a CWS.

That said, Australia does have very good, safe, water - admittedly statistically better than the US overall. Not bad for a country that has less people and a smaller GDP than California... Thanks for the nuke sub order btw.

Originally Posted by JPA Cate

is not a case of Ozzies bashing the US, imo, but more that people who live here are highly concerned with the quality of their water supplies, and the concern spreads to other cruising destinations, as well.

It certainly didn't come across that way (IMO). That said: if people there are so concerned about the "quality of their water supplies, why( again) do they all have PFAS in their blood?

Originally Posted by JPA Cate

Boatman 61 had some serious problems on a delivery because he trusted the town water somewhere in FL.

That's is unfortunate, but is it absolutely certain that it was a problem with the town water system? Or was it (more likely) an issue at the place where he filled up?

Bottom line is: we are all responsible for what goes into our tanks, and ultimately into our bodies. And it is up to us to take whatever precautions we deem necessary. And, as far as your understanding that "water sources in the US are becoming slowly more and more jeopardized"? As evidenced by your own link, that's wrong. The US has some of the cleanest/safest water on the planet, even if it doesn't come up to 'Australian expectations'.

[CaptainMarkS]

IMHO, use of chlorine in tanks is risky, especially if the water in those tanks is used for a fresh water flush for a watermaker (assuming you have one). The chlorine will damage the RO membrane. Instead, I use hydrogen peroxide. Target: 25 ppm = .0025% by volume.

[rslifkin]

Originally Posted by CaptainMarkS

IMHO, use of chlorine in tanks is risky, especially if the water in those tanks is used for a fresh water flush for a watermaker (assuming you have one). The chlorine will damage the RO membrane. Instead, I use hydrogen peroxide. Target: 25 ppm = .0025% by volume.

If you chlorinate tanks and have a watermaker, yes, caution is required. Either you need a non-chlorinated water source for flushing, or you need to be careful about chlorine concentration and have an adequate carbon filter system (sized based on flow rate during watermaker flush) to strip enough chlorine out of the flush water to avoid membrane damage.

[CaptainMarkS]

Originally Posted by rslifkin

If you chlorinate tanks and have a watermaker, yes, caution is required. Either you need a non-chlorinated water source for flushing, or you need to be careful about chlorine concentration and have an adequate carbon filter system (sized based on flow rate during watermaker flush) to strip enough chlorine out of the flush water to avoid membrane damage.

Why not just use H2O2 (hydrogen peroxide), be safe, and not worry about chlorine? Seems simpler and just as effective as a biocide.

[Brendan]

Originally Posted by malbert73

Install a high quality filter and then drink away out of your tanks. I use a seagull but there are cheaper ways to do it out there. Not just carbon but also filters out microorganisms

I just three hours ago received my Seagull IV filter, hope to have it installed tomorrow.
I've been drinking water out of my boat tanks for the last 2.5 years. I did put in some chemical cleaner and manually cleaned in the parts of the tank where I can reach.

1991 Taswell with two tanks, both on, but main tank has to be empty before back up tank gets drawn on.

[SailFastTri]

Not intending to change the subject, nor to diminish the importance of the many good suggestions above about potable water.
Those who are concerned about harmful pathogens and chemical pollutants would be well advised to eat only unprocessed or minimally processed plant foods. Eating (even handling) fish and other types of meat presents a far greater risk to human health than water, generally speaking. The casual way people clean food preparation surfaces, especially on recreational boats, does not kill most harmful pathogens, and neither does cooking. The methods don’t develop adequate heat in most cases, nor stop cross contamination on surfaces. Then there’s the issue of concentration of pollutants in animals higher in the food chain.
We eat plant-based but will provision for guests who want meat and dairy if meat is precooked before being brought aboard. We don’t want raw meats/fish aboard.

[merrydolphin]

Originally Posted by S/V Illusion

Chlorine efficacy as a disinfectant is dependent on residual Cl concentration which dissipates rapidly as a function of agitation, temperature, humidity, contaminants on the tank walls and piping and fittings, etc… so there is no definitive answer to your question.

If you want to be safe, 1. Don’t consume tank water or 2. Consume only bottled water from known sources. And most POU carbon filters provide nothing more than a false sense of safety.

Now in my late seventies. I have used tank water my whole life from early teens up. Never an issue. Use common sense. Once a year shock the whole system with chlorine, dump it and use. I know that there are people that won’t use their tanks, only bottled. (And bottled has it’s issues too) Quality, micro plastics etc. I use a quality filter ( Home Depot) for drinking only) a separate spigot in the galley. It is not just carbon. Change the element about twice a year. And for decades we didn’t even have that. My policy on source was that if the locals didn’t regularly drink it. I didn’t either. Eg. Parts of Mexico. Then I bought the local Garaphonies ( 5 gal jugs.) and pored them in the tanks. We also had a great water catchment for rain. A good tropical shower could fill our 200 gal of tanks. We later got a Spectra watermaker. Loved it as it would run just on solar power. So minimal battery drain and no generator necessary. While in the San Blas, islands of Panama, we drank water from the jungle rivers. We went as the locals way up the river to near the source……big waterfalls. Never had an issue drinking it for about 8 months. Of course suplimented by rain water. Yes, as long range, and long term cruisers I think that our tummies were pretty well use to different water sources and locales. But again NEVER an issue. Get away from bottled. It’s not so healthy, expensive, it’s terrible for the environment and is a pita.

My goodness, if you have a boat designed with tankage, maintain it and use it. If you are concerned: Get a good full sized water filter cartridge type. Get a cartridge that filters nearly everything. Put a drinking spigot on the counter any you are better than bottled for safety.