Disinfecting SS water tanks with bleach?

[Intifada]

First of all, can I add bleach to a full SS water tank? If so how many ml of bleach per litre of water? Thanks.

[peghall]

If you go the thread " Rotten egg smell downstream of filter in the plumbing forum, you'll find complete instructions for using bleach to recommission (sanitize) the fresh water system and why it's safe to us in metal tanks in post #11


--Peggie

[TheOffice]

Peggy, Thanks!

[JPA Cate]

What if it leaks?

Hi, Intifada,

In places where the water quality is unknown and it is murky as it comes from the tap, we used 1Tablespoon to 10 gallons (about 15 ml to 4/5 l) and never had a problem with our s/s tanks in the 14-15 years we owned the boat after putting in the tanks. If the water is murky from particulates (as happens some places after rainfalls), let the jugs set for a few hours, then, then don't run the syphon hose all the way to the bottom of the jug, so that the water is cleaner when it goes into the tank. Then, rinse out the jug to get rid of the sludge. It will keep your charcoal filter alive longer, and it will filter out any remaining chlorine. You can also boil it out if you are going to make tea or coffee. It is mostly all gone in a day or so, in any event, as the chlorine percolates out of the water while in the tank. We never had any problem from the water or the tanks with this usage.

Ann

[denverd0n]

Google "bleach and stainless steel." You will get hundreds of hits explaining how bleach will oxidize stainless steel. Bleach should only be used on stainless at relatively low concentrations for wiping it down, and then should be rinsed off.


I know that some people do, but I would not add bleach to my water in a stainless steel tank.

[Mike OReilly]

We just completed the shocking of our ss tank using Peggy's formula . We do this at the beginning of each season, and have done so for over a decade now with this boat. So far, so good. Our tank seems fine, and the water tastes great.

BTW, this year our process took a lot longer since our boat has sat for over 2.5 years through Covid. We're back now, and slowly bring the old girl back to life.

[MJH]

Originally Posted by Intifada

First of all, can I add bleach to a full SS water tank? If so how many ml of bleach per litre of water? Thanks.

Here is a Practical Sailor note on the subject I copied to my computer years ago:

There is a standard sanitizing procedure for recreational vehicles (ANSI A119.2 section 10.8) that works just as well for boats. We've added a few details, but the bones of it come straight from the code and have been reviewed and accepted by the U.S. Public Health Service.
• Turn off the hot water heater until finished.
• Remove any carbon canisters or micron rated filters. Remove any faucet aerator screens. Wire mesh pump protection strainers should stay in place. The plumbing will very likely slough off a layer of bacteria during later flushing steps.
• Clean and remove the vent screen and flush the vent hose.
• Use either following methods to determine the amount of common household bleach needed to sanitize the tank.
1. Multiply gallons of tank capacity by 0.13; the result is the ounces of bleach needed to sanitize the tank. This is 1/8 cup of plain bleach (no fragrance) per 10 gallons.
2. Multiply liters of tank capacity by 1.0; the result is the milliliters of bleach needed to sanitize the tank.
• Mix the proper amount of bleach within a 1-gallon container of water. This will provide better mixing and reduce spot corrosion of aluminum tanks.
• Pour the solution (water/bleach) into the tank and fill the tank with potable water.
• If possible, allow some solution to escape though the vent. (If the vent is exterior, prevent any spillage into local waters.) This will sanitize the vent line.
• Open all faucets (hot and cold) allowing the water to run until all air is purged and the distinct odor of chlorine is detected. Leave the pressure pump on.1
• The standard solution must have four hours of contact time to disinfect completely. Doubling the solution concentration reduces the contact time to one hour.
• When the contact time is completed, drain the tank. Refill with potable water and purge the plumbing of all sanitizing solution. Repeat until bleach is no longer detectable.
• If the smell of bleach persists after two refill and drain cycles, add a teaspoon of hydrogen peroxide per 20 gallons and mix. The peroxide will oxidize the hypochlorite to chloride (salt) and oxygen, neutralizing the bleach. Any excess peroxide will be harmless to drink and will have no taste. Peroxides are common ingredients in commercially available water freshening preparations like those we tested. Don't use vinegar, which can ferment, undoing all of your hard work.
• Replace all filters and the vent screen.
• Note for aluminum tanks: Some sailors are afraid of using bleach in aluminum tanks for fear of rapid corrosion. This shouldn't be a concern for infrequent cleaning when the recommended dosage and time is observed. As an alternative, we found PuriClean to be an effective sanitizer, and it was non-corrosive toward aluminum.

Part One of Frye's three-part series on onboard water quality, a test of water tank pre-filters, began in the June 2015 issue; the July 2015 issue focuses on keeping water clean and fresh; look for part three in the August 2015 issue. You can follow Frye's other experiments and sailing adventures at Sail Delmarva

Good Luck.

[Ninedotsix]

In industrial water treatment practice, our firm uses sodium chlorite (8%), which sanitizes water piping and tanks very effectively, while not contributing the obnoxious chlorine smell, or halomethanes that result from use of sodium hypochlorite, aka “bleach”.
In US, there is Starbrite Aqua Shock, and another version for routine maintenance after the shock.
These are chlorite (not hypo-) and about 5%, as I recall.
I use chlorite for maintenance onboard, and it is my standard, since it doesn’t impart the strong odor.
Perhaps more important for SS tanks is a condition called chloride stress corrosion. Maybe read up on that. Chloride ion can induce stress cracking of the SS material. Trying to weld up the cracks makes it worse, take it from this voice of experience looking back to 50 years ago, and a miserable few days.
Having written those words, I’ll add that the water treatment techs use chlorite on SS, so check it out.
I had the treatment protocol in computer, but believe that’s gone now. NSF has info online, I think in public space.
Fair Winds ~ PM

[jmschmidt]

You can find a formula for this on the internet.