purify water in tanks

[Cheechako]

Bleach has been used for decades for this purpose. Many boats with SS tanks have used it. Just dont over use it and stay with minimum levels of treatment.
SS tanks corrode regularly in boats, all that I have have seen, including some I replaced, were corroded from the outside where they sit on damp supports, or at the seams where they were welded.
My feeling is that the odds of having a tank corrode from bleach are lower, and take many more years, than other issues.

Boats that take on city water have already had low level bleach in the tank. "64% of US community water treatment systems use chlorine as a disinfectant."

[S/V Illusion]

Originally Posted by rslifkin

But a chlorine residual (of reasonable level) can be removed from the water before consumption with adequately sized carbon filters.

The problem with carbon filtration is that efficacy is dependent on residence time and most point of use filters are too small. Peroxide is generally dissipated simply by aeration at the faucet.

Neither are either reliable or completely effective which is why many prefer to consume only bottled water or RO water which we have but can have its own problems.

[rslifkin]

Originally Posted by S/V Illusion

The problem with carbon filtration is that efficacy is dependent on residence time and most point of use filters are too small.

Agreed. That's why I included the caveat of having a reasonable chlorine residual and adequately sized filters. Excessive chlorine or too small filters will let too much chlorine through.

[wrwakefield]

I defer to Practical Sailor's authorative information on this, and most topics.

I can't imagine the time and cost to repair/replace our two SS 110 gallon potable water tanks layed against the hull- under everything...

In case this is useful.

Cheers! Bill

[JPA Cate]

Hi, Rascally,

With our boat before this one, we had s/s water tanks (but only 50 gallons total capacity), and many times took on questionable water. We used 1 Tablespoon regular (not extra strong) chlorine bleach for each 10 gallons, and filtered the drinking water thereafter with a charcoal filter to remove the chlorine taste. Neither the tanks nor ourselves suffered from the process over the 17 years we owned the boat.

On a different note, don't know if you're going to use a giant bladder or jerry jugs of some sort for water. If the collapsible jugs route is yours, as it was ours, where you can determine the muddiness of the water, if you let it set, treated, overnight, then don't syphon it all out of the jugs into the tank. Leave the last inch or so in the jug and pour that overboard, like silt running out of a river. Most of the sediment will settle, and who needs mud in their water tank? It may even mean another trip to the waterfall or spigot or stream...and we really never know what's happened upstream.



Ann

[Ballsnall]

Originally Posted by Rascally

I guess my original question wasn’t clear enough.

Q - If “today” I’m taking on water that is suspect, is there chemical treatment that I can buy or make that will purify the water.

The problem I see is, how will you know when you take on suspect water? It's usually only by getting sick that you might suspect the water and even then it's not an accurate method. If it's once in a blue moon, just dose your tanks with chlorine. Regular occurrence, filtration or a plastic stand alone drinking water tank.
If you do dose your SS tank with chlorine then leaving the fill cap off for a day or two will allow the chlorine gas to dissipate faster and be less of a concern.

[s/v Jedi]

I know I hate the taste of chlorine in the water and I have no idea what water treated with hydrogen peroxide tastes like.

I do know that you can filter suspect water with a Seagull IV filter (https://www.amazon.com/Seagull-X-1F-...2-8997e41410bb) and drink it. You can also use one of those LifeStraw filters: https://www.amazon.com/gp/product/B006QF3TW4

Or use the affordable filter I listed earlier.

If you can’t do any of that, you could at least boil any consumption water until you can buy a filter. It will not deal with chemicals, but it will deal with many viruses and bacteria.

Also, when you have multiple tanks, you can treat a tank with chlorine and wait a while for it to evaporate.

[Jammer]

Originally Posted by Rascally

Should I to take from this discussion that there isn’t a chemical treatment to purify water in SS or aluminum tanks that doesn’t harm the tanks? (aside from using chlorine at 0.5ppm and hoping the resulting damage is minuscule when compared to the expected lifespan of the tank; I would hope for 40 years, but think even 0.5ppm might reduce that).

Chlorine is terrible on tankage and plumbing. Throughout the developed world, the use of chlorinated water causes uncounted, untold millions of dollars of damage to water distribution and residential and commerical plumbing and fixtures. It damages galvanized steel. It damages PEX. It damages PVC supply pipes and drain pipes. It damages polyethylene tubing in spite of the fact that stabilizers are added to the plastic specifically to deal with chlorine. Historically it was so tough on polybutylene tubing that polybutylene tubing was withdrawn from the market.


It is also the only known agent that will sanitize water and prevent the transmission of cholera and other water-borne diseases, that is usable at scale and that does not have adverse effects on health. The public health benefits make it well worth the millions of dollars of damage that it does.


You should chlorinate the water in your tanks unless you are getting water from a supply that is already chlorinated. You should do this even if you aren't using tank water for drinking. You should not overdo it because corrosion of stainless steel comes not from proper use of chlorination but from excessive use of chlorination. The right way to do it is use test strips and set a free chlorine level that is right for your situation but there are a lot of people that just add a certain proportion of bleach and call it good. Ann for example posted 1 Tbsp per 10 gallons, which is 1.5 mL per gallon. I use 1 mL per gallon. Either dose is a guess, the only way to get it right is to use test strips because the incoming water chemistry varies.


You can also filter the water, either as you put it in the tank or as you take it out, as pointed out upthread.


You can also boil the water.


Chemically, you can use ozone instead of chlorine, but it's impractical on a boat and has its own corrosion problems.


You can also use iodine instead of chlorine. It's less corrosive and is widely used for cleaning industrial food handling surfaces, bulk tanks for milk and other foods, and so on. It's rinsed off in those applications, but you can use it for purifying water. The problem is that it can be toxic, with quite a bit of individual variation in sensitivity. I used iodine for water purification while backpacking in the 1980s before portable submicron filtration was available. There is an excellent NIH article here, covering risks and dose: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1638306/


You will also be able to taste the iodine if an effective dose has been used.

[Jammer]

Originally Posted by Ballsnall

The problem I see is, how will you know when you take on suspect water?

All water is suspect by the time it's in the tank on your boat, unless it is already chlorinated, or came from an onboard RO that's plumbed directly to the tank.



It is possible to get pure, uncontaminated water from a well or an RO or other shoreside treatment. By the time it is exposed to air and contamination at the hose bib on the dock, and exposed to contamination in the hose you use, and the fill port and vent line to your tank, it is no longer microbiologically pure. Carrying water in jugs or whatever compounds the problem, because there are more opportunities for contamination.


I lived in rural locations for many years where we had wells and rainwater or got water from the lake or a spring and other iffy sources. I like city water. I like that fact that somebody besides me is testing the chlorine level every day and sending a sample to the lab from time to time as a check on the process.

[s/v Jedi]

Originally Posted by Jammer

All water is suspect by the time it's in the tank on your boat, unless it is already chlorinated, or came from an onboard RO that's plumbed directly to the tank.



It is possible to get pure, uncontaminated water from a well or an RO or other shoreside treatment. By the time it is exposed to air and contamination at the hose bib on the dock, and exposed to contamination in the hose you use, and the fill port and vent line to your tank, it is no longer microbiologically pure. Carrying water in jugs or whatever compounds the problem, because there are more opportunities for contamination.


I lived in rural locations for many years where we had wells and rainwater or got water from the lake or a spring and other iffy sources. I like city water. I like that fact that somebody besides me is testing the chlorine level every day and sending a sample to the lab from time to time as a check on the process.

I never drink city water. Many have perished or have life long severe health problems caused by city water. I think you are misguided on this.

[wefleenor]

I made 12 trips to sub-Saharan Africa with students to work on water and sanitation projects. I always used colloidal silver to treat the water I drank with total success. Many students used fancy backpacking filters with limited success. Make sure you use colloidal silver and not silver nitrate of silver chloride. I haven't gone in 4 years, but I used to buy a product called Silverdine.

[AKA-None]

Originally Posted by s/v Jedi

I never drink city water. Many have perished or have life long severe health problems caused by city water. I think you are misguided on this.

Sure if you get water from flint Michigan or there’s fracking near your water source

[Jammer]

Originally Posted by s/v Jedi

I never drink city water. Many have perished or have life long severe health problems caused by city water. I think you are misguided on this.

I am a fool when it comes to most things; perhaps you're right.



Before there was chlorinated water, my great-grandmother died of typhoid. Over 1000 children died yesterday from diarrhea with most cases caused by pathogens in the water supply.

[Spindrift NH]

I believe you can use iodine to purify water.

[Loredo]

To the OP,
wefleenor said : "I always used colloidal silver to treat the water I drank with total success."



During the past 15 years I've always used this product (colloidal silver) for my (often suspect) water with great success:


https://shop.yachticon.de/en/drinkin...hlorine-100-ml


To my best knowledge, colloidal silver does no damage to SS tanks.
Just as an anecdote, my previous boat had three water tanks. I did "forget" to use one of them for +/- two years. When I switched to that tank expecting all kinds of ugly stuff the water instead was still perfect / no smell.