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How much chlorine for 40 gallon tank?

Jul 8, 2005
460
Jeanneau 389 Grosse Pointe Farms, MI
Reading Peggie's book, page 49 says 4 ounces mixed in a gallon and use one gallon for 5 gallons of water. If I am correct, that means 32 ounces of chlorine for 40 gallons.

Practical Sailor suggests 1 tablespoon per 10 gallons or 4 tablespoons for 40 gallons. 4 tablespoons is 2 ounces.

Many versions of this online.

What is the correct amount? Is one for shock and the other for maintenance?
 
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Likes: patbratton
Feb 21, 2013
3,613
Hunter 46 Point Richmond, CA
You are on the right track............for shock chlorination to remove molds, mildew, fungi and bacteria in the freshwater tank per page 59 of "Get Rid of Boat Odors" 2nd edition..........make a "chlorine solution" consisting of 2 ounces (1/4 cup) household bleach (5% sodium hypochlorite) and 1 gallon of water. Then pour the soution into empty tank at a ratio of 1 gallon of solution per 5 gallons of tank capacity. For 40 gallons add 8 gallons of solution. That works out to 16 ounces (1/2 quart) of household bleach. Then follow the subsequent steps including fill (with potable water), hold, drain, fill, drain, add vinegar solution, hold, drain, fill, drain.

As Practical Sailor proposes Keeping Water Clean and Fresh | Practical Sailor (practical-sailor.com) for emergency disinfection add 1 tablespoon of household bleach per 10 gallons and for routine disinfection at 2 ppm add 1 teaspoon of household bleach per 50 gallons.
 
Last edited:
Dec 2, 1997
8,089
- - LIttle Rock
This is what I actually wrote on p.59 of the "New" GROBO 2nd Edition:

"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!)"

You can drive yourself up a tree calculating 2 oz (1/4 cup)/gallon. Much easier to just divide 50/10 to arrive at the amount of bleach per 10 gallons tank capaciy, , then 10 x 4 to arrive the correct amount for a 40 gallon tank...or 10 x 7.5 for a 75 gallon tank...etc...

--Peggie
 
Last edited:
Jan 7, 2011
2,829
Oday 322 East Chicago, IN
Reading Peggie's book, page 49 says 4 ounces mixed in a gallon and use one gallon for 5 gallons of water. If I am correct, that means 32 ounces of chlorine for 40 gallons.

Practical Sailor suggests 1 tablespoon per 10 gallons or 4 tablespoons for 40 gallons. 4 tablespoons is 2 ounces.

Many versions of this online.

What is the correct amount? Is one for shock and the other for maintenance?
Are you trying to shock your tank, or keep The water fresh?

Peggy will probably object, but I add a splash (few tablespoons) to each of my 30 gallon tanks during the summer months. Maybe I don’t use the water fast enough, but the tanks get a bit skanky in warm weather, and I find a little bleach helps. I brush my teeth with it, but don’t usually drink it.

This year, I am trying to use only 1 of the tanks, and emptied the other one…I need some place to put an A/C unit and maybe some additional batteries, so testing to see if I can get by on one tank.

Greg
 
Dec 2, 1997
8,089
- - LIttle Rock
What is the correct amount? Is one for shock and the other for maintenance?
The directions in my book should be used ONLY to recommission the fresh water system--the entire system, not just the tank:

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.

Y'all might try reading ALL the directions...they don't end with the amount of bleach to use...
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 booze!

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.

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.

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...you'll know when it is because the water will become cool.

--Peggie
 
Jul 8, 2005
460
Jeanneau 389 Grosse Pointe Farms, MI
This is what I actually wrote on p.59 of the "New" GROBO 2nd Edition:

"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!)"

You can drive yourself up a tree calculating 2 oz (1/4 cup)/gallon. Much easier to just divide 50/10 to arrive at the amount of bleach per 10 gallons tank capaciy, , then 10 x 4 to arrive the correct amount for a 40 gallon tank...or 10 x 7.5 for a 75 gallon tank...etc...

--Peggie
Thank you.
I will have to get the latest edition. Mine is quite old and quite used!
The directions in my book should be used ONLY to recommission the fresh water system--the entire system, not just the tank:

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.

Y'all might try reading ALL the directions...they don't end with the amount of bleach to use...
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 booze!

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.

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.

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...you'll know when it is because the water will become cool.


--Peggie
Peggie,

Just to be clear.
If we follow your directions, it should be safe to drink the water?
I might be OK washing dishes with it, but not sure about drinking it.
I know the vinegar will improve the taste/smell.

Chris
 
Dec 2, 1997
8,089
- - LIttle Rock
If we follow your directions, it should be safe to drink the water?
Yes!! The water is safe to use for everything you'd use municipal water out of a faucet on land for, including drinking it.

It's important to know that these are not MY directions... 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.

I found them in the owners manual for a 1985 boat my late husband and I bought in 1989 and saved them. You can find them on most RV sites.

--Peggie
 
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Dec 2, 1997
8,089
- - LIttle Rock
Btw...This is how I used to do it. I'd bring a couple of gallons of water in milk jugs to the boat to use during the recommissioning.

Last thing before turning in for the night I'd drain the water tank and fill it with the bleach solution...then, making sure to leave the water pump on, go to bed.
First thing the next morning I'd make coffee with the water I'd brought and enjoy the first cup while I drained the solution through every faucet on the boat. Made breakfast while refilling the tank with fresh water, ate it while draining that tankful. Got dressed while I filled the tank for the last time. All done without screwing up even one hour of my day.

This is where you should add the vinegar and water to that tankfull IF NEEDED and go sailing.Drain and refill in a few days.

And btw...Recommissioning each spring will remove any antifreeze taste/smell from your water. You will most likely need the vinegar water to accomplish that.

--Peggie
 
Last edited:
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Likes: jssailem
Jul 8, 2005
460
Jeanneau 389 Grosse Pointe Farms, MI
Btw...This is how I used to do it. I'd bring a couple of gallons of water in milk jugs to the boat to use during the recommissioning.

Last thing before turning in for the night I'd drain the water tank and fill it with the bleach solution...then, making sure to leave the water pump on, go to bed.
First thing the next morning I'd make coffee with the water I'd brought and enjoy the first cup while I drained the solution through every faucet on the boat. Made breakfast while refilling the tank with fresh water, ate it while draining that tankful. Got dressed while I filled the tank for the last time. All done without screwing up even one hour of my day.

This is where you should add the vinegar and water to that tankfull IF NEEDED and go sailing.Drain and refill in a few days.

And btw...Recommissioning each spring will remove any antifreeze taste/smell from your water. You will most likely need the vinegar water to accomplish that.

--Peggie
Thank you, Peggie.

I think the amount of bleach should kill anything living!

I also like the white vinegar which i have not done on the past.

I am going to follow ALL OF THESE directions now.

Chris
 
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MikeWT

.
Sep 30, 2018
5
Beneteau 343 Bristol
Is it ok to flush the water with bleach mixture into the ocean? Because the bleach evaporates? Or would it be better to perform this sanitizing on land so the mixture goes into the ground in the boatyard?
 
Dec 2, 1997
8,089
- - LIttle Rock
I've never seen a single objection to flushing the bleach solution directly overboard in all the years I've published these directions in my books and online.

--Peggie
 
Sep 25, 2008
6,267
Alden 50 Sarasota, Florida
Is it ok to flush the water with bleach mixture into the ocean? Because the bleach evaporates? Or would it be better to perform this sanitizing on land so the mixture goes into the ground in the boatyard?
To clarify, discharging of anything is a violation of Federal law. Technically, discharging fresh water into salt water is as well although no one has ever enforced that prohibition.
Also, hypochlorite doesn’t evaporate but rather dissolves and disperses into the water column. If any chlorine evolves, it is a trivial amount.
Having said all that, there are more important things to worry about.
 
Dec 2, 1997
8,089
- - LIttle Rock
To clarify, discharging of anything is a violation of Federal law. Technically, discharging fresh water into salt water is as well although no one has ever enforced that prohibition.
I don't know where you got that idea...I suspect you may have misinterpreted laws that pertain only to large commercial vessels--cruise ships etc--to also pertain to recreational vessels. If that were true for recreational vessels it would not be legal to discharge gray water directly overboard...but with the exception of a very few closed inland lakes, it is legal to discharge gray water directly overboard in all US waters. Nor would it be legal use most of the boat cleaning products on boats in the water.

U.S. "no discharge" laws ONLY apply to SEWAGE ("human body wastes and the wastes from toilets and other receptacles intended to receive or retain body waste.")--and only in waters specifically designated "no discharge" by the EPA. In all other US waters it's legal to discharge treated waste from a USCG certified Type I or II MSD. Nor do they prohibit "discharge" of body waste directly from the lee rail (although you could run afoul of indecent exposure laws), only that which goes into a container first...making "bucket and chuck it" illegal.

The only other prohibitions pertain to oily discharge.

--Peggie
 
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Sep 25, 2008
6,267
Alden 50 Sarasota, Florida
In that case you should be famliar with the parts of the CFR that apply to recreational vessels.

--Peggie
I am. As well as a host of others beyond the boat perspective but are still applicable regardless of the source. It is therein where the prohibitions lie including regulations promulgated pursuant to the CWA with which you may be unaware.

It is largely an academic distinction as enforcement is very limited to more egregious issues but offered simply to clarify that it isn’t okay to flush, pour, dump, discharge, etc... stuff like bleach or even pure water, both of which can adversely affect certain marine organisms if discharged in sufficient quantity.