purify water in tanks

[Rascally]

What to use to purify water in a stainless tank?

Hello everyone,

I’ve read what I think must be every comment on water tank cleaning and recommissioning.

In one comment Peggy Hall says that warm climates might require you to “treat each tankful to purify”.

Of course, that runs against her strong warning about damage caused by continuous use of small amounts of chlorine for each tankful of water. She recommends a shock treatment, but not continuous use of chlorine.

To be clear, I’m not talking about cleaning up a problem, I’m talking about taking on suspect water, water you need to put in your tanks because that’s all you’re going to have access to for the entire season.

Understanding that most chemicals will, over time, cause problems (corrosion) to stainless to aluminum tanks, what does one use to purify water in a stainless tank?

[goboatingnow]

“Chlorine is very aggressive to stainless steels. The Nickel Institute guidelines for continuous exposure at ambient temperatures (~20˚C) and neutral pH (~ pH7), are that 304 can cope with 2ppm chlorine and 316 ~5ppm chlorine. In alkaline solutions (pH>7) higher concentrations are possible but this does not help much in swimming pools or drinking water. Chlorine frequently causes corrosion problems. Chlorine attack can occur with bleach laden washdown water if pools form in drains which are usually empty. Chlorine concentrations in droplets or water films immediately above a still pool or water tank can be higher than the chlorine level in the bulk water. When dosing concentrated chlorine into pipes or tanks, it must be well mixed otherwise concentrated streams will eat out downstream elbows or tank walls near the chlorine inlet.


Much higher concentrations can be used for short periods as the attack on the stainless steel must initiate and form a stable pit for failure to occur. The American Water and Wastewater Association permits 25ppm for 24 hours in cases of emergency disinfection. The food industry can use up to 100ppm in hot water for minutes followed by rinsing and/or passivation. It is an effective biocide because the kill rate depends on (exposure time) * (concentration of biocide) but the stainless steel is resistant to the chlorine for the relatively short, high concentration exposure.”

[peghall]

In one comment Peggy Hall says that warm climates might require you to “treat each tankful to purify”.


Please point me to where you read that, because I did NOT say that and wouldn't because as you--correctly this time-said, it run against my warning against continuous use of chlorine.


As the instructions for the "shock treatment' clearly state, "The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated."

I'll be glad to post the complete instructions if you'd like to have them.

--Peggie

[kayakerChuck]

Hi Peggy!

I'll be re-commissioning a friend's system this week. A fresh posting of your procedure would be great!

Thanks!

[Rascally]

Originally Posted by peghall

In one comment Peggy Hall says that warm climates might require you to “treat each tankful to purify”.


Please point me to where you read that, because I did NOT say that and wouldn't because as you--correctly this time-said, it run against my warning against continuous use of chlorine.


As the instructions for the "shock treatment' clearly state, "The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated."

I'll be glad to post the complete instructions if you'd like to have them.

--Peggie

Hey Peggy…. Mold in a fresh water tank: comment #5.

In that post it was clear you were referencing water from outside the USA, suspect water.

Regardless…. My question is about how best to deal with suspect water. I’m presently in the southern Caribbean, and there has been a recommendation during a visit to a physician, that water can be suspect during time of heavy rains. My friend was quite sick, and physician suspects the local water supply - which is normally reliable.

Regardless of the risk being real or not, the question remains, what is the best course of action for suspect water in a SS tank?

Randy

[Jammer]

I would suggest submicron filtration. The General Ecology Seagull IV filter was the standard for this for many years but there are now competing products that have similar specifications and are cheaper.


If you filter the water as you fill the tanks, you may not get everything, but you'll get the overwhelming majority including all of the troublesome and hard-to-kill cysts. You will also reduce the chlorine load of the water making it easier to get the free chlorine level to the desired point if you wish to treat chemically also.



0.2 ppm chlorine is sufficient for disinfection if sustained until the point of use. 2 ppm is usually the recommended maximum. There are test kits. If you don't overdo it the tanks will be fine.

[peghall]

It's not MY procedure...you'll find the same instructions on most of the major RV sites:


RECOMMISSION FRESH WATER SYSTEM
Although most people think only in terms of the tank, the plumbing is actually the source of most foul water, because the molds, mildew, fungi and bacteria which cause it thrive in damp dark places, not under water. There are all kinds of products sold that claim to keep onboard water fresh, but all that’s really necessary is an annual or in especially warm climates, semi-annual recommissioning of the entire system—tank and plumbing. The following recommendations conform to section 10.8 in the A-1 192 code covering electrical, plumbing, and heating of recreational vehicles. The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated.

Before beginning, turn off hot water heater at the breaker; do not turn it on again until the entire recommissioning is complete. Icemakers should be left running to allow cleaning out of the water feed line; however the first two buckets of ice—the bucket generated during recommissioning and the first bucketful afterward--should be discarded…bleach does absolutely nothing to improve the flavor of good Scotch!

1 Prepare a solution using 1 quart or liter of household bleach (5% sodium hypochlorite solution)/50 gallons of water tank capacity.

2. Complete filling of tank with fresh water. Open each faucet and drain cock until air has been released and the entire system is filled. Do not turn off the pump; it must remain on to keep the system pressurized and the solution in the lines

3. Allow to stand for at least three hours, but no longer than 24 hours.

4 Drain through every faucet on the boat (and if you haven't done this in a while, it's a good idea to remove any diffusion screens from the faucets, because what's likely to come out will clog them). Fill the tank again with fresh water only, drain again through every faucet on the boat.

5. To remove excess chlorine taste or odor which might remain, prepare a solution of one quart white vinegar to five gallons water and allow this solution to agitate in tank for several days by vessel motion.

6. Drain tank again through every faucet, and flush the lines again by filing the tank 1/4-1/2 full and again flushing with potable water.

People have expressed concern about using this method to recommission aluminum tanks. While bleach (chlorine) IS corrosive, its effects are cumulative. So the effect of an annual or semi-annual "shock treatment" is negligible compared to the cumulative effect of holding chlorinated city water in the tank for years. And it’s that cumulative effect that makes it a VERY bad idea to add a little bleach to each fill. Not only does it damage the system, but unless you add enough to make your water taste and smell like a laundry, it’s not enough to do any good. Even if it were, any “purifying” properties in chlorine evaporate within 24 hours, leaving behind only the corrosive properties. Nevertheless, it's a good idea to mix the total amount of bleach needed for recommissioning in a few gallons of water before putting it into an empty stainless or aluminum tank.

An annual or semi-annual recommissioning according to the above directions is all that should be necessary to keep your water tasting and smelling as good as anything that comes out of any faucet on land. If you need to improve on that, install a water filter. Just remember that a filter is not a substitute for cleaning out the system, and that filters require regular inspection and cleaning or replacement.

[Rascally]

Originally Posted by peghall

It's not MY procedure...you'll find the same instructions on most of the major RV sites:


RECOMMISSION FRESH WATER SYSTEM
Although most people think only in terms of the tank, the plumbing is actually the source of most foul water, because the molds, mildew, fungi and bacteria which cause it thrive in damp dark places, not under water. There are all kinds of products sold that claim to keep onboard water fresh, but all that’s really necessary is an annual or in especially warm climates, semi-annual recommissioning of the entire system—tank and plumbing. The following recommendations conform to section 10.8 in the A-1 192 code covering electrical, plumbing, and heating of recreational vehicles. The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated.

Before beginning, turn off hot water heater at the breaker; do not turn it on again until the entire recommissioning is complete. Icemakers should be left running to allow cleaning out of the water feed line; however the first two buckets of ice—the bucket generated during recommissioning and the first bucketful afterward--should be discarded…bleach does absolutely nothing to improve the flavor of good Scotch!

1 Prepare a solution using 1 quart or liter of household bleach (5% sodium hypochlorite solution)/50 gallons of water tank capacity.

2. Complete filling of tank with fresh water. Open each faucet and drain cock until air has been released and the entire system is filled. Do not turn off the pump; it must remain on to keep the system pressurized and the solution in the lines

3. Allow to stand for at least three hours, but no longer than 24 hours.

4 Drain through every faucet on the boat (and if you haven't done this in a while, it's a good idea to remove any diffusion screens from the faucets, because what's likely to come out will clog them). Fill the tank again with fresh water only, drain again through every faucet on the boat.

5. To remove excess chlorine taste or odor which might remain, prepare a solution of one quart white vinegar to five gallons water and allow this solution to agitate in tank for several days by vessel motion.

6. Drain tank again through every faucet, and flush the lines again by filing the tank 1/4-1/2 full and again flushing with potable water.

People have expressed concern about using this method to recommission aluminum tanks. While bleach (chlorine) IS corrosive, its effects are cumulative. So the effect of an annual or semi-annual "shock treatment" is negligible compared to the cumulative effect of holding chlorinated city water in the tank for years. And it’s that cumulative effect that makes it a VERY bad idea to add a little bleach to each fill. Not only does it damage the system, but unless you add enough to make your water taste and smell like a laundry, it’s not enough to do any good. Even if it were, any “purifying” properties in chlorine evaporate within 24 hours, leaving behind only the corrosive properties. Nevertheless, it's a good idea to mix the total amount of bleach needed for recommissioning in a few gallons of water before putting it into an empty stainless or aluminum tank.

An annual or semi-annual recommissioning according to the above directions is all that should be necessary to keep your water tasting and smelling as good as anything that comes out of any faucet on land. If you need to improve on that, install a water filter. Just remember that a filter is not a substitute for cleaning out the system, and that filters require regular inspection and cleaning or replacement.

Thanks for clarification Peggie.

[Ballsnall]

Originally Posted by Rascally

Regardless of the risk being real or not, the question remains, what is the best course of action for suspect water in a SS tank?
Randy

I am assuming you have activated charcoal filtration for your drinking water. I would suggest the addition of a UV filtration unit to handle any pathogens.

[Rascally]

Originally Posted by Ballsnall

I am assuming you have activated charcoal filtration for your drinking water. I would suggest the addition of a UV filtration unit to handle any pathogens.

I was hoping for something more suitable for the times we’ll be taking on suspect water.

Island water supplies are quite reliable given that RO is so common. Used and refilled every few weeks has proven to be quick satisfactory. I would hazard a guess that 98% of the yachties who live aboard, using their water systems daily, do not have filters or UV. This, because the islands they visit have excellent water.

But of course there are exceptions. And this is my question.

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).

Assuming there isn’t recommended way to purify the water, then yes, filtration and UV would be the option.

[s/v Jedi]

Originally Posted by Rascally

I was hoping for something more suitable for the times we’ll be taking on suspect water.

Island water supplies are quite reliable given that RO is so common. Used and refilled every few weeks has proven to be quick satisfactory. I would hazard a guess that 98% of the yachties who live aboard, using their water systems daily, do not have filters or UV. This, because the islands they visit have excellent water.

But of course there are exceptions. And this is my question.

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).

Assuming there isn’t recommended way to purify the water, then yes, filtration and UV would be the option.

I’m afraid your guess isn’t correct. The #1 best option is to stop taking in shore water, switching to rain water and your own RO system.
The #2 option is filtration. Jammer is right, the Seagull IV filter has been the gold standard and was given the “water purification” classification.

A cheaper option: this housing: https://www.amazon.com/gp/product/B002WDS366 with these cartridges: https://www.amazon.com/gp/product/B003ZVZ79U or even these: https://www.amazon.com/gp/product/B084DPJW37
This option stillhas NSF/ANSI certification.

We do more. We catch rain water and have a 40gph watermaker. Then after our fresh water pump, we first have the linked-above filter housing with a pleated sediment filter, followed by a T fitting, followed by a second filter housing with the carbon block filter. The output from the 2nd filter goes to a consumption water faucet in the galley, as well as to the watermaker flush input; the rest of the water comes from the T fitting in between the two filter housings.

We think the RO installation is crucial for blue water cruising and self reliance.

[s/v Jedi]

I am not an expert on water purification using additives, but I think instead of chlorine you can also use hydrogen peroxide?

[Rascally]

Originally Posted by s/v Jedi

I am not an expert on water purification using additives, but I think instead of chlorine you can also use hydrogen peroxide?

Peroxide has been discussed thoroughly in these forums, and my understanding from reading here, is they sufficient H.peroxide to be effective at purifying water, makes the water sufficiently unpleasant to use/consume.

I see from your other comment above, and dozens of comments in these forums, there’s many ways to purify water, filtration, UV, install an RO system, etc.

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 lack of suggestions for same, with comments all around the subject matter, leads me to think, No, there is nothing. And that’s ok. Unfortunate for me, but it what it is.

In future, when time and money permits, I’ll work toward a better system. Today, I’ll assume my water is suspect and deal with it.

[S/V Illusion]

Originally Posted by Rascally

Peroxide has been discussed thoroughly in these forums, and my understanding from reading here, is they sufficient H.peroxide to be effective at purifying water, makes the water sufficiently unpleasant to use/consume.

Actually an effective residual level of Cl has far more unpleasant taste than does peroxide. The biggest advantage is using peroxide is that the disinfection property lasts longer.

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.

it.

Only one - bottled water. No filter can remove everything and most serve only to provide a false sense of security. Similarly, there is no magic chemical treatment.

[rslifkin]

Originally Posted by S/V Illusion

Actually an effective residual level of Cl has far more unpleasant taste than does peroxide. The biggest advantage is using peroxide is that the disinfection property lasts longer.


Only one - bottled water. No filter can remove everything and most serve only to provide a false sense of security. Similarly, there is no magic chemical treatment.

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