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

[LifesBetterWhenYoureBeating]

Hi everyone,

I have 2 water tanks on my boat and a couple valves that let me choose which one(s) to use for my fresh water systems. I thought it'd be a good idea to keep the smaller tank for emergencies, so I've closed its valve and only use the other one (which is also the one that gets fed by my water maker).

The smaller tank was filled several months ago and recently I tasted its water and it seemed OK, but I'm wondering if I should periodically use all the water from the emergency tank and refill it? If so, how often would be recommended?

Thanks in advance!

Sent from my SM-A225F using Cruisers Sailing Forum mobile app

[Jebtrois]

You can purify and/or preserve the water with chemicals such as bleach and it will keep for a long time. However, to the extent that you can, I would turn the water over as often as reasonable through regular use. While the older water can be made safe so it won't harm you, it is certainly less palatable when it is otherwise pretty easy to refresh it.
JEB

[garyfdl]

Are you planning a long voyage/passage where you might require a back-up water supply? If 'no' I wouldn't worry about it (and this is from a guy who overthinks everything!)

Were it me, I'd cross connect the tanks and use water from both, and monitor the level(s).

As already mentioned, there are chemicals you can add to keep the water safe. Plain bleach will do; it only takes a tiny amount. Check online for the ratio of bleach to water in order to purify.

[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.

[sailorboy1]

I have drank water from tanks that was 3 months old. A little musky smelling that is removed by my carbon drinking water filter tap

[MicHughV]

I've always had a habit of of putting a capful (about half a teaspoon) of bleach in my water tanks, every time I filled them. Tanks are about 150 gallons contained in two tanks. I also have charcoal filters in line with the internal boat water system. This seems to do the trick to keep them clean. I don't generally drink the tank water, but do use tank water for cooking, etc.
I've been doing this for many years without a lick of problems anywhere.

Your tank water lines are probably clear plastic hose somewhere inside the boat.....might be worth it to inspect these to see if you see any residue, or other contaminants.

[SailingHarmonie]

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.

How did anyone ever survive before the bottling companies of the world started selling their ridiculously overprice environmentally disastrous product to people who are terrified of everything?

If you want to be safe lock yourself in a tiny room and don’t eat or drink ANYTHING!

[S/V Illusion]

Originally Posted by SailingHarmonie

How did anyone ever survive before the bottling companies of the world started selling their ridiculously overprice environmentally disastrous product to people who are terrified of everything?

If you want to be safe lock yourself in a tiny room and don’t eat or drink ANYTHING!

So you have nothing constructive to add?

[JPA Cate]

Ah, cut Harmonie some slack, man!

Jim and I have used treated fresh water that had been sitting in the tanks and not only never worried about it, but also never suffered for it in any way.

I understand water sources in the US are becoming slowly more and more jeopardized, but if once you have taken in either city water or rain water which you have adequately chlorinated, as Sailorboy1 wrote, the charcoal filter will remove the chlorine taste.

We carry 800 liters (211 gallons). No problem, ever.

Ann

[Gard]

Contrary to popular belief, water has no expiration date (even if the bottled water says otherwise) - purified water in a sterilized and pollutant free container can be stored for billions of years and still be safe to drink. But it will lose its freshness rather quick. My emergency water at home is stored in food grade plastic containers with a bit of chlorine, and is replaced once a year (but could be stored for ages and be safe).

Using chlorine - one drop/liter or 5ml/10L and agitate and wait 30 minutes. Safe to drink (in all but extreme circumstances)

The problem on a boat is that there is no way to prevent contamination of the tanks. The water must be replaced frequently. The tanks, pipes, etc must be cleaned regularly as well. How often and to what extent depends on the amount of contamination. Also, if you want really clean water, simply cleaning with chemicals alone won't cut it - you need to do it mechanically (sponges, etc) plus chemicals.

I usually keep drinking water in sterile airtight containers. Not so much because I am worried about getting sick, as I am concerned about taste.

With a tank cleaned yearly and properly, making sure I put water from an uncontaminated source, using an uncontaminated hose - I would not be concerned about safety - even with water a year old - especially if from an emergency tank that can be sealed off (including ventilation).

[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

[Chotu]

Originally Posted by JPA Cate

Ah, cut Harmonie some slack, man!

Jim and I have used treated fresh water that had been sitting in the tanks and not only never worried about it, but also never suffered for it in any way.

I understand water sources in the US are becoming slowly more and more jeopardized, but if once you have taken in either city water or rain water which you have adequately chlorinated, as Sailorboy1 wrote, the charcoal filter will remove the chlorine taste.

We carry 800 liters (211 gallons). No problem, ever.

Ann

Same here.

I have more concern about using water from a water maker actually. In case it has too much sodium still in it.

but natural freshwater, properly stored with a little bit of chlorination? basically lasts indefinitely. And the charcoal filter gets rid of the flavor of the chlorine.

Perfect system.

[valhalla360]

Originally Posted by Gard

Contrary to popular belief, water has no expiration date (even if the bottled water says otherwise) - purified water in a sterilized and pollutant free container can be stored for billions of years and still be safe to drink. But it will lose its freshness rather quick. My emergency water at home is stored in food grade plastic containers with a bit of chlorine, and is replaced once a year (but could be stored for ages and be safe).

Using chlorine - one drop/liter or 5ml/10L and agitate and wait 30 minutes. Safe to drink (in all but extreme circumstances)

The problem on a boat is that there is no way to prevent contamination of the tanks. The water must be replaced frequently. The tanks, pipes, etc must be cleaned regularly as well. How often and to what extent depends on the amount of contamination. Also, if you want really clean water, simply cleaning with chemicals alone won't cut it - you need to do it mechanically (sponges, etc) plus chemicals.

I usually keep drinking water in sterile airtight containers. Not so much because I am worried about getting sick, as I am concerned about taste.

With a tank cleaned yearly and properly, making sure I put water from an uncontaminated source, using an uncontaminated hose - I would not be concerned about safety - even with water a year old - especially if from an emergency tank that can be sealed off (including ventilation).

Unless you get some bad water, turning it over frequently is typically plenty to keep the system perfectly safe. Fresh water supply has minimal organic contamination that can spur growth and assuming some is city water which is typically chlorinated, it's just not a big deal.

No such thing as sterile in practical application, so waste of time trying to maintain it.

On the other hand let it sit for 6-12 months, best to empty the water system completely as that minimal contamination has time to let things grow. Purposely leaving a tank full and not using it makes no sense unless part of a crossing (as an emergency backup) but as soon as the crossing is over, start turning the water over again.

[rslifkin]

Originally Posted by Chotu

but natural freshwater, properly stored with a little bit of chlorination? basically lasts indefinitely. And the charcoal filter gets rid of the flavor of the chlorine.

That's exactly it. If you start with "safe to drink" water and keep it slightly chlorinated so nothing grows in it, then run it through a good carbon filter setup, you get good water even when it's been sitting for a while. The carbon strips most of the chlorine back out, and given enough contact time with the carbon, it'll remove some amount of other contaminants as well, so the output water is likely to be better than the water that went into the tank.

[garyfdl]

Originally Posted by JPA Cate

I understand water sources in the US are becoming slowly more and more jeopardized

Not sure where your hearing that, but I would say its a gross overstatement.