cancel
Showing results for 
Search instead for 
Did you mean: 

% bleach to sanitize fresh water tanks

rvshrinker
Explorer III
Explorer III
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_.pdf

And this Idaho DEQ website says dilute 1000:1:

https://www.deq.idaho.gov/media/517665-disinfecting-water-wells-storage-tanks-fact-sheet-0612.pdf

What is the correct concentration of bleach to disinfect the water tanks?
34 REPLIES 34

ppine
Explorer II
Explorer II
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
Explorer
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.
2017 Ruby Red Platinum F450 - my kids call her "Big Red"
2018 Grand Design Reflection 28bh

K3WE
Explorer
Explorer
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
Explorer
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.
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board

aftermath
Explorer II
Explorer II
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
2017 Toyota Tundra, Double Cab, 5.7L V8
2006 Airstream 25 FB SE
Equalizer Hitch

garmp
Explorer II
Explorer II
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.
Our 2351D Phoenix Cruiser, Jack, has turned us from campers into RVers and loving it!

coolmom42
Explorer
Explorer
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.
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board

4x4van
Explorer
Explorer
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...
We don't stop playing because we grow old...We grow old because we stop playing!

2004 Itasca Sunrise M-30W
Carson enclosed ATV Trailer
-'85 ATC250R, '12 Husky TE310, '20 CanAm X3 X rs Turbo RR
Zieman Jetski Trailer
-'96 GTi, '96 Waveblaster II

JimK-NY
Explorer II
Explorer II
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
Explorer
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.
1999 Newmar MACA 3796 F53 6.8L
2016 Ford Edge Sport
Roadmaster Sterling A/T with Brake Buddy Select

ssthrd
Explorer
Explorer
rvshrinker wrote:
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_.pdf

And this Idaho DEQ website says dilute 1000:1:

https://www.deq.idaho.gov/media/517665-disinfecting-water-wells-storage-tanks-fact-sheet-0612.pdf

What is the correct concentration of bleach to disinfect the water tanks?


In a municipal water system, if chlorine is used as a disinfectant, it is introduced to the mains at around 1 to 2 PPM. The idea is to chlorinate at a level that maintains a trace level at the end of the system, so maybe up to 4 PPM is required to maintain a trace amount. A large system may have more than one disinfection station depending on system size and water source quality.

The American Water Works Association (AWWA) has been around since before the 1900's, and has been the accepted source for benchmark water testing and recommendations for many utility standards used by the US, Canada, and other countries around the world.

AWWA has procedures which detail solutions to disinfect public water mains and storage facilities (tanks) using several different methods and products including bleach which you mention above. In my 40 years of experience with building, testing and disinfecting municipal water systems, I have used three different methods depending on the situation involved-could be part of new pipeline construction, or maybe a main break. Their standards are in ANSI/AWWA C652-19.

https://www.awwa.org/Portals/0/Awwa/Publishing/Standards/C652-19LookInside.pdf?ver=2020-02-25-153628-643

OK, after all that, the disinfection standard for domestic water supply is 25 parts per million (PPM) chlorine to water which I had always exceeded just to be sure. I used 50 PPM. After the solution is introduced into the pipe or tank, it must (according to AWWA) be left for 24 hours, and then tested for a residual. A sample is then taken to a lab to test for fecal and total coliform counts. After another 24 hours have passed, another sample is taken and tested. If both samples are negative for coliform, the water is deemed to be safe to drink.

If the same pipe/tank was filled with 50 PPM, and the flow was regulated so that there was 3 hours minimum contact time throughout the system/tank, then the same testing procedure is followed immediately after flushing the system.

I realize that the above is lengthy, but the standards are the same for any domestic water application. Drinking water from a travel trailer tank is no different than drinking from a domestic water supply in a home. I have read in this forum in the last number of years posts from people who are not sure what the proper procedure should be. If you are OK with making up a solution at 25PPM, you should be good to go.

I would hazard a guess that most people do not do this because they really don't know much about it. For me at the first of the season, I chlorinate my RV system with 50 PPM, more or less, leave it for 24 hours, flush and use. After that, if the trailer sits unused for a month for example, I will put a couple of ounces in the filler hose and then fill the tank and flush the system a couple of times or whatever it takes to get rid of the chlorine taste.

I'm not saying that it's OK to do that, only that that's what I do.

Hope this is helpful.
2014 Keystone Laredo 292RL
2013 Palomino Maverick 2902
2018 GMC 3500HD, 4x4, 6.5' box, SRW, Denali, Duramax, Andersen
DeeBee, JayBee, and Jed the Black Lab

The hurrier I go the behinder I get. (Lewis Carroll)

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


That article deals with using bleach to disinfect drinking water, not tank sanitization.
The Yost Outpost
Gilbert, AZ
2007 GMC Sierra Classic 2500HD, Duramax LBZ
2019 Nash 23D

teejaywhy
Explorer
Explorer
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?
The Yost Outpost
Gilbert, AZ
2007 GMC Sierra Classic 2500HD, Duramax LBZ
2019 Nash 23D

Boon_Docker
Explorer II
Explorer II
"I think I'm done..."

I would say so, now go out and have fun.