First time doing this chore.Most sources say to use household bleach 1/4 cup for every 15 gallons of fresh water capacity. Mix required bleach amount in some fresh water, pour into your tanks, fill with potable water, let sit, drain, rinse.However other sources say 1/4 cup for 10 gallons.For a 60 gallon freshwater tank, this is either 1 cup or 1.5 cups of bleach.But according to this fact sheet from the Northeastern University Dept of Environmental Health Sciences, bleach should be concentrated at 5000 - 20,000 ppm to disinfect. 5% bleach is 50,000 ppm, 10% bleach 100,000 ppm, etc. This would imply diluting 5% bleach no more than 10:1 to get to a concentration of 5000 ppm, the minimum for disinfecting. Then the 60 gallon tank needs ~5 gallons of 5% bleach and 55 gallons of water to be diluted properly for disinfection.That’s a big difference.https://www.northeastern.edu/ehs/wp-content/uploads/2014/12/Bleach-Fact-Sheet-Draft.ejc2_.pdfAnd this Idaho DEQ website says dilute 1000:1:https://www.deq.idaho.gov/media/517665-disinfecting-water-wells-storage-tanks-fact-sheet-0612.pdfWhat is the correct concentration of bleach to disinfect the water tanks?

I have always used 8 oz of household bleach for my 30 gallon tank.1000:1 sounds right. As per your link above.

Per the EPA at https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water

the minimum ratio will work, but it might need to soak for a long time. If you increase the ratio you cut the soak time. For instance my Jayco manual says take the tank capacity and multiply by .13. So my tank needs 5.2 oz of bleach. 40*.13=5.2 That will take 4 hours to disinfect. However if I double the bleach to 10.4 oz. My soak time goes down to 1 hour. To add the bleach I hook the water hose to the trailer tank. Then I pour 1cup bleach into the faucet end of the hose and screw it onto the spigot. turn on the water and let the tank fill.If I go with the standard 1/4 cup per 10 gallons I would add one cup (8oz) to my 40 gallon tank. This makes a stronger solution than the minimum (5.2 oz) without being so strong it damages the internal components. So most people will just take the easy route of saying 1/4 cup per 10 gallons over 4 hours. Below is the excerpt from my owners manual.Sanitizing the Potable Water SystemWARNING: Failure to sanitize the potable water system could result indeath or serious illness.1. Use one of the following methods to determine the amount of common householdbleach needed to sanitize the tank. Multiply “gallons of tank capacity” by 0.13; the result is the ounces of bleachneeded to sanitize the tank. Multiply “liters of tank capacity” by 1.0; the result is the milliliters of bleachneeded to sanitize the tank.2. Mix the proper amount of bleach into a container of water.3. Pour the solution (water/bleach) into the tank and fill the tank with potable water.4. Open all faucets (Hot and Cold) allowing the water to run until the distinct odor ofchlorine is detected.5. The standard solution must have four (4) hours of contact time to disinfectcompletely. Doubling the solution concentration allows for contact time of one (1)hour.6. When the contact time is completed, drain the tank. Refill with potable water andpurge the plumbing of all sanitizing solution.If there is a problem of excessive chlorine odor and taste after the sanitizing process, followthe above procedures using a solution of baking soda (1/2 cup added to one gallon (4 liters)of water per 15 gallons (60 liters) of tank capacity) or vinegar (one quart added to fivegallons (20 liters) of water per 15 gallons (60 liters) of tank capacity.)Your demand water system is now ready for use. Refer to instructions on filling the tankand utilizing the system in the “Setting Up Camp...” chapter

more is better doesn't really apply to the time it takes for bleach to do its job. as an oxidizer it needs a certain amount of time to breakdown the various organic barriers employed by microbes. so more doesn't mean faster sanitizing, it just means wasted time and water as you'll spend a lot more time rinsing it out.Just what do you think has been growing in your tank over the winter anyway? are you planning to use a non-potable source, so the bleach not only has to sanitize the tank, but also the entire volume of water?

After draining the bleach, I suggest adding a cup or two distilled vinegar when you refill the tank. Drain again and refill with water only.

% bleach to sanitize fresh water tanks | Good Sam Community

ppine
Explorer II
Sep 15, 2020
None of theses measurements are critical. The suggestion to charge a well head which is for thousands of gallons of water is around 2 quarts.

A cup, a few ounces, 5 ounces will work fine if you let it sit for awhile before draining and flushing your tank.
Lexx
Explorer
Sep 15, 2020
Here's my two cents as a retired healthcare provider. I am concerned not only with the bacteria in the tank, but also in the waterlines.

So to that end, I use the 1/4 cup of Clorox bleach per 10 gal formula. Since my fresh water tank is 43 gal, I use a bit over a cup. I bypass my water filters and siphon the bleach into the tank. Then I fill my fresh water tank until I see water coming out of the overflow pipe.

At that point I run all the faucets and shower in the trailer so that I know there's chlorinated water in the lines. I let that sit for 24 hours. Then the next day I dump that chlorinated water, fill the tank with fresh water and run the lines, dump the rest of the water, refill the tank again, and then dump it again. This way I know I've gotten rid of most of the chlorinated water and I'm confident that the waterlines are fairly clean.

Biofilm in the waterlines is a big issue. Bleach is one of the better ways to kill the biofilm. There are other commercial products we used to use in the office but I'm not sure of their compatibility with our plumbing systems in the trailer.
K3WE
Explorer
Sep 10, 2020
4x4van wrote:
Wow, alot of people spending alot of time/effort/worry. I live in the US, which has arguably among the best quality domestic water supplies in the world. If you are using well water, then I can see the use of bleach for an occasional sanitizing, but otherwise?

I've owned 3 RVs, over the course of 32 years. Never sanitized any of the 3. Drink/cook/bathe using the onboard tank. Store with the water (remaining after a trip) for a month or more between trips, simply top off for the next trip. In fact, I only drained the tank once, after the RV had sat for about 2 years during the time when gas was $5+/gallon, since there was a bit of "plastic" taste. Otherwise no bad taste, no sickness, no issues. Of course, we also grew up drinking water out of the green plastic garden hose as well, so...

Yeah there’s a lot of over thinking here, but doing an annual bleach treatment doesn’t make one a germophobe...

Some folks also enjoy optimizing things...can’t fault them either.
coolmom42
Explorer II
Sep 02, 2020
garmp wrote:
Sanitizing the fresh water tank.
Has anyone used this? Looks pretty slick, but what the heck it's just another $30 gizmo to add to the RV paraphernalia list. Just when I thought the cost of the RV ended as we drove off the lot. Live & learn.

Completely unnecessary. Just use bleach.
aftermath
Explorer III
Aug 25, 2020
teejaywhy wrote:
SAR Tracker wrote:
Boon Docker wrote:
RoyF wrote:
After draining the bleach, I suggest adding a cup or two distilled vinegar when you refill the tank. Drain again and refill with water only.

What is the reason for the vinegar mixture?

Removes the bleach taste

How do you get rid of the vinegar taste?

Sanitize your tank with bleach. :B
garmp
Explorer II
Aug 24, 2020
Sanitizing the fresh water tank.
Has anyone used this? Looks pretty slick, but what the heck it's just another $30 gizmo to add to the RV paraphernalia list. Just when I thought the cost of the RV ended as we drove off the lot. Live & learn.
coolmom42
Explorer II
Aug 23, 2020
Boon Docker wrote:
RoyF wrote:
After draining the bleach, I suggest adding a cup or two distilled vinegar when you refill the tank. Drain again and refill with water only.

What is the reason for the vinegar mixture?

Helps neutralize any remaining bleach along with its taste and odor.
4x4van
Explorer III
Jul 07, 2020
Wow, alot of people spending alot of time/effort/worry. I live in the US, which has arguably among the best quality domestic water supplies in the world. If you are using well water, then I can see the use of bleach for an occasional sanitizing, but otherwise?

I've owned 3 RVs, over the course of 32 years. Never sanitized any of the 3. Drink/cook/bathe using the onboard tank. Store with the water (remaining after a trip) for a month or more between trips, simply top off for the next trip. In fact, I only drained the tank once, after the RV had sat for about 2 years during the time when gas was $5+/gallon, since there was a bit of "plastic" taste. Otherwise no bad taste, no sickness, no issues. Of course, we also grew up drinking water out of the green plastic garden hose as well, so...
JimK-NY
Explorer II
Jul 06, 2020
STBRetired wrote:
If you have the whole house water filter installed in your rig, be sure to remove the filter cartridge before sanitizing and put in a brand new one when you are done. The activated carbon in those filters will remove chlorine, and the massive amount of chlorine in the sanitizing solution (as compared to normal city water) will exhaust the filtering capacity of the cartridge.

That is exactly why you should think twice about getting a whole house water filter. It is really a bad idea to remove the chlorine. Instead consider a sediment filter and then a final filter for drinking water either at the tap or use a Brita or other similar system.
STBRetired
Explorer
Jul 06, 2020
If you have the whole house water filter installed in your rig, be sure to remove the filter cartridge before sanitizing and put in a brand new one when you are done. The activated carbon in those filters will remove chlorine, and the massive amount of chlorine in the sanitizing solution (as compared to normal city water) will exhaust the filtering capacity of the cartridge.

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