Sterilization of water tank

I did a quick search but only came up with one thread but it did not say how they did it.
I have an RV and sterilize my tank once a year. Just wondering if the process is the same. In the RV we use standard bleach (1-2 cups) with a mostly full tank (80gallons).
The tank in my vessel is fiberglass as opposed to plastic in the RV.

Oh don’t you worry- Peggie will be along shortly-

Bleach works quite well.

A bit of bleach, then run a bunch of fresh water through the system to clear out the smell.

That's way more bleach than needed for 80 gallons. Here is a link to the CloroxCleaning Tips and Advice | Clorox® web site:

Thank you all for your help!

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. This is the same method that's been recommended on at least 90% of RV maintenance sites for more than 30 years...I've also included 'em in both my books:

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 chlorine solution using one gallon of water and 1/4 cup (2 oz or 25 ml) Clorox or Purex household bleach (5% sodium Hypochlorite solution ). With tank empty, pour chlorine solution into tank. Use one gallon of solution for each 5 gallons of tank capacity. (Those are the “official” directions. They work out to 1 quart or litre of bleach/50 gallons of water tank capacity , which is MUCH easier to calculate!)

[FONT=&quot]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 [/FONT]

[FONT=&quot]3. Allow to stand for at least three hours, but no longer than 24 hours.[/FONT]

[FONT=&quot]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. [/FONT]

[FONT=&quot]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. [/FONT]

[FONT=&quot]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.[/FONT]

[FONT=&quot]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.[/FONT]

[FONT=&quot]To keep the water system cleaner longer, USE your fresh water...keep water flowing through system. The molds, fungi, and bacteria only start to grow in hoses that aren't being used. Before filling the tank each time, always let the dock water run for at least 15 minutes first...the same critters that like the lines on your boat LOVE the dock supply line and your hose that sit in the warm sun, and you certainly don't want to transfer water that's been sitting in the dock supply line to your boat's system. So let the water run long enough to flush out all the water that's been standing in them so that what goes into your boat is coming straight from the water main.
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[FONT=&quot]--Peggie
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Thank you Peggie!

The OP can’t see inside his tank. With a poly tank and a flashlight held against you can see all the grass like stuff churning around while filling the tank. Anybody use a filter for that? I plumbed one up but took it out for a reason I can’t remember.

Aha Peggie has arrived as I projected you would. Read no other replies- the Head Mistress is here and we bow! ;-)

About 20 years ago we bought an express cruiser from a guy in Minnesota who was (still is, I think) a food safety scientist with Cargill. Since then, we've always followed his protocol:

1) 1/2 teaspoon clorox per 10 gallons of water. Add this at every fill. Also add this again if the water in your tank remains unused for more than a week or two (especially in summer).

2) put a 'brita' or equivalent filter on the faucet(s) you use for drinking/cooking water. These filters use activated carbon that will remove the chlorine.

If you are regularly adding the chlorine with your fill-ups, you can use a 5-micron filter. If not, use a 1-micron filter to be extra sure you catch any nasty bugs that come in from your dockside/marina water supply.

Since then, we've never had to sterilize a tank, they just stay clean.

The other benefit is that we no longer load up our boats with bottled water. Leaves more room for booze, and good for the environment.

Bajabuzz said:

Thank you Peggie!

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You're quite welcome. Fwiw, I first found those directions in the owners manual for a 1985 340 SeaRay my late husband and I bought in 1989.


--Peggie

I've always read 1 cup bleach to 60 gallons of water capacity, fill tank, pressurize system, run each faucet for a minute or two, leave pressurized for 4 hour dwell time, then empty (through each faucet) and refill system. Drain and refill one more time if bleach smell is still excessive.
Has worked well for us for 12 years.

sum escape said:

I've always read 1 cup bleach to 60 gallons of water capacity, fill tank, pressurize system, run each faucet for a minute or two, leave pressurized for 4 hour dwell time, then empty (through each faucet) and refill system. Drain and refill one more time if bleach smell is still excessive.
Has worked well for us for 12 years.

Click to expand...

To disinfect a system, a basic rule of thumb to shock disinfect with
chlorine indicates we need to bring the chlorine concentration to about
50 ppm. Clorox contains 5.25% chlorine, so do a bit of math.

For a 100 gallon tank, multiply 100gal. x 50 ppm -> 100 X (50/1,000,000)
= .005 gal.
So we need to add .005 gal of chlorine.
Household bleach (Clorox) is typically 5.25% chlorine, so 1 gallon of
Clorox = 0.0525 gallon of chlorine.
For our 100 gallon system, .005gal/0.0525= 0.09524 gallons of bleach.
That converts to ~ 12 oz. So, 1-1/2 cup of Clorox is needed to create a
concentration of 50 ppm in 100 gal.
Contact time for a 50 ppm concentration is 6 hrs. For 24 hrs. contact
time, the concentration can be reduced to 10 ppm, or for 100 gal. tank,
a dose of 4 oz. Clorox.

These are conservative concentrations, meaning they're already
overkill. More isn't necessarily better - enough is enough! Higher
concentrations won't make the bugs more dead, they'll only complicate
the flushing and rinsing of the system. Once the tank is disinfected, it
should be flushed & rinsed with clean water, then it's ready to use. A
carbon taste & odor filter installed in the main supply line downstream
of the pump will remove any remaining chlorine taste, and help with
keeping the water fresh tasting and enable you to dispense with the
plastic bottles. Once the tank is disinfected, there's no need to
routinely disinfect it other than perhaps an annual preventive shock.
So keeping tanks suitable for domestic use simply involves filling
them with clean water and using it!

Hope that helps! Drink tank water!

Maerin said:

To disinfect a system, a basic rule of thumb to shock disinfect with
chlorine indicates we need to bring the chlorine concentration to about
50 ppm. Clorox contains 5.25% chlorine, so do a bit of math.

For a 100 gallon tank, multiply 100gal. x 50 ppm -> 100 X (50/1,000,000)
= .005 gal.
So we need to add .005 gal of chlorine.
Household bleach (Clorox) is typically 5.25% chlorine, so 1 gallon of
Clorox = 0.0525 gallon of chlorine.
For our 100 gallon system, .005gal/0.0525= 0.09524 gallons of bleach.
That converts to ~ 12 oz. So, 1-1/2 cup of Clorox is needed to create a
concentration of 50 ppm in 100 gal.
Contact time for a 50 ppm concentration is 6 hrs. For 24 hrs. contact
time, the concentration can be reduced to 10 ppm, or for 100 gal. tank,
a dose of 4 oz. Clorox.

These are conservative concentrations, meaning they're already
overkill. More isn't necessarily better - enough is enough! Higher
concentrations won't make the bugs more dead, they'll only complicate
the flushing and rinsing of the system. Once the tank is disinfected, it
should be flushed & rinsed with clean water, then it's ready to use. A
carbon taste & odor filter installed in the main supply line downstream
of the pump will remove any remaining chlorine taste, and help with
keeping the water fresh tasting and enable you to dispense with the
plastic bottles. Once the tank is disinfected, there's no need to
routinely disinfect it other than perhaps an annual preventive shock.
So keeping tanks suitable for domestic use simply involves filling
them with clean water and using it!

Hope that helps! Drink tank water!

Click to expand...

Both of our formulas are significantly less than what Peggy has suggested.

sum escape said:

I've always read 1 cup bleach to 60 gallons of water capacity, fill tank, pressurize system, run each faucet for a minute or two, leave pressurized for 4 hour dwell time, then empty (through each faucet) and refill system. Drain and refill one more time if bleach smell is still excessive.
Has worked well for us for 12 years.

Click to expand...

Tom
I have seen ( and use) the concentration you mention - 1/4 cup / 15 gal or 1 cup / 50-60 gal referenced for boat and RV water tank sanitizing but as I recall the recommended residence time was 12 hrs.

I believe the time required to sanitize is a function of concentration and guessing that's the difference between the various concentrations quoted but frequently omit the recommended time.
I looked but could not find a good table of concentrations vs time req'd.

Oh my God ! I've been doing it wrong.
I've been putting in one large dissolved tablespoon of Bi-Carbonate of soda in hot water to 100 litres to sterilize the water.

But good for an upset stomach

sum escape said:

Both of our formulas are significantly less than what Peggy has suggested.

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She just makes a stronger drink. I find nothing wrong with her recommendations. She was schooling me when.... oh, I probably shouldn't go there.



Just for clarification, I tried to find an authoritative recommendation for chlorine concentration for disinfecting water storage tanks. In my plumbing experience some contracts, particularly public funded, required piping systems to be disinfected with a solution of 200ppm with contact time of 1 or 2 hrs. Most technical recommendations deal with household or on site water delivery systems that involve a well or other storage method. The 50 ppm is sufficient to disinfect with a contact time of 6 hrs. This from the State of Oregon. WHO and AWWA also refer to the 50 ppm concentration for disinfection. So it's safe to use. Again, 200 ppm will also kill, the contact time would only need to be a half hour or so, but it's overkill, and then there's concern re: discharging the super chlorinated solution into surface waters. It's toxic to wildlife, so there's some rationale for using just what's needed, and increasing the contact time to 6 or even 24 hours.

There's also a method where the dosage is calculated at 50 ppm based on the total tank volume, fill the tank 10%, apply the full dose, allow to stand for an hour, then incrementally fIll the tank to capacity, and the appurtenant piping, then let stand for another 6 hours.

I'm not sure a 100 or 200 gallon marine tank warrants what might be considered over-thinking a simple task. I'm in the dose it 50 ppm, get it into the system, then let it stand overnight & flush it- camp. Unless the system is really contaminated, it'll be fine. We're talking maintenance of an otherwise functional system. If you're working on a tank that's been sitting for years, you may want to bump that dosage up to 100 or 200 ppm.

There's not a thing wrong with OD'ing the tank. But the recommended dosage will be just as effective in disinfecting, and probably won't leave as much residual smell or taste, so may be a little faster to complete.



Either way accomplishes the disinfection. If you have a method that you're happy with, super!

Drink tank water!

Just a thought. Any reason you couldn't just add 50 gallons of water (say, to a 100 or 200 gallon tank), flush all the lines with it, and let the sloshing action of the boat work for any unfilled space in the tank?

After all, as Peggy points out, the pipes, fittings and hoses are the main target.

I'm assuming the tank started out pretty clean, from regular use and annual treatment. Obviously if you've got stuff growing in there already, you want to top it off.

Maerin
Thanks - that's exactly my understanding and practice.
I am usually not in a big hurry so leaving overnight is easy - in fact we usually just use the 1st tank for cleaning, showering, etc but use jugs for drinking, coffee, cooking etc. We rarely just dump the first 60 gals.

The directions I posted are not MY directions...I found them years ago and saved them. Please note this in the first paragraph: "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."


That doesn't seem to leave a lot of room to argue the concentration. But it's YOUR boat and there's no rule requiring you to follow those directions.


--Peggie

HeadMistress said:

The directions I posted are not MY directions...
That doesn't seem to leave a lot of room to argue the concentration. But it's YOUR boat and there's no rule requiring you to follow those directions.
--Peggie

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Peggie
No argument intended - at least from my perspective - unless you contend that the contact time is unrelated to the concentration used?

My feeling is that RVIA is an industry related standard and manufacturers would naturally be concerned with the time required. A procedure that would take 24 hrs would not be as manufacturing friendly as one being completed in 3 hrs. Many of us fill one day and dump the next day so 12 - 24 hr contact time is very reasonable.

There are many papers with recommended concentrations between 50 PPM and 200 PPM and different contact times ranging from 2 to 24 hrs. In fact the the food / restaurant industry standards cite higher concentrations for surface sanitizing that are effective with 3-5 min contact time.

As always - thanks for your knowledge & contributions

Formula from Shurflo

Found tank sanitation instructions in a Shurflo water pump owners manual. From the manual:
>2 oz of bleach per 15 gallons of capacity (1 cup per 60 gallons)
>Flush through all faucets, leave pump on and let rest 4 hours. Double the solution concentration for a one hour contact time.
>Drain and refill a time or two to reduce odor. Residual chlorine odor is not harmful.

Hopefully this is a "credible" source

HeadMistress said:

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."

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I suspect the high concentrations in this formula are to deal with the possibility of a contaminated system. If your system has NOT been contaminated, then the lower concentrations would be completely adequate. All of the sources that I've read -- that get into the details of the proper PPM for different purposes -- specify higher concentrations for known contamination, and lower concentrations to sanitize questionable, but reasonably clean, sources.


Nit-picking, but I would also point out that we are talking about "sanitizing" a system, not "sterilizing" it. Your water system does not need to be sterile, and true sterilization goes WAAAY beyond the kind of sanitization that we're talking about.

Any help/harm to running the solution through a fresh water head when sanitizing? Flush a couple of times to get it into the system to clean. Or is this a waste (sorry) that will just mess up the good things the aerobic bacteria have going on in my holding tank by dumping chlorine on them?

Never can say "aerobic bacteria" without getting a strange mental picture of them all down there on floor mats in little bacteria workout suits, jumping up and down, pumping their little bacteria arms to get their heart rate up....

Pretty obvious - bleach is the key to keeping fresh water tanks and plumbing lines clean.

I've been boating for over 60 years. From 5th grade onward I took on [was promoted to - lol] the task of being "water-boy" aboard dad's boats.

Dad taught me well in regard to how, when, why and in what amount to add bleach to fresh water tank. Has worked well for me ever since... btw... I'm still "water-boy" and very proud of it!

There have been many mentions of bleach proportions, hours to let set, how many times to full flush, how often to add bleach and flush... etc. So I won't bother to add my 2 cents on detail instruction. All I can say is of the posts I read most are completely in the ball park on keeping fresh water fresh aboard boat.

Would like to add this comment: IMO... A little [not too much] extra bleach is a lot better than any amount of extra contaminents/buggs in your water system.

Listen to Peggie... She Knows!!

Let me take this one step further. Obviously, if a boat is wintered over up north, the water must be drained. But if the boat is idle for 6 months in a tropical climate (no freezing) is it better to leave the tanks and water system full (no air, everything is in water, and no bugs can grow unless it's moist, but not underwater)? We've been leaving our fuel and water systems full for the last 10 years, but....inquiring minds want to know!

We have lived aboard for 10 years. Our tanks are SS. We get water from dozens of places each year from Canada to the keys. We have never yet found a need to sterilize our water system. The water is usually from municipal sources which has chlorine in it. We do have a carbon filter just after the water pump.

denverd0n said:

Nit-picking, but I would also point out that we are talking about "sanitizing" a system, not "sterilizing" it. Your water system does not need to be sterile, and true sterilization goes WAAAY beyond the kind of sanitization that we're talking about.

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Correct, I should have entitled thread "sanitizing". Just an annual "clean up" to be sure we are safe as we live aboard and cycle the water every 10 days to 2 weeks. We don't buy bottled water and lug it to the boat, the fresh water system and a Brita serve us well.

We use UV light to sterilize our water as it goes into the tank.