% bleach to sanitize fresh water tanks

[rvshrinker]

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?

[rvshrinker]

That sounds great. I used 10% bleach and used 1 cup for 80 gallons. Drained, filled, ran faucets, let it sit overnight, drained again including water heater, filled with fresh, ran faucets till no bleach smell. I think I'm done, but the water heater has a very slow leak, so I need to pull the anode and tape the threads and close it up again.

[JimK-NY]

Years ago I got tired of all the advice and personal opinions. I did a literature search and found actual scientific studies and recommendations. Sorry I did not save the webpage and could not find it. I am positive of the results.

The recommended bleach concentration is 1/4 cup of standard household bleach for every 15 gallons. Standard household bleach is in the range of 5-6%. The recommended soak time was 1 hour, not 4 hours, no 12 hours, not overnight, but 1 hour.

There is probably little or no harm to soaking for a couple of hours or so but it is best to avoid prolonged soaking and especially avoid high bleach concentrations. Bleach is not friendly with pump seals, etc.

I could not find any solid, scientifically based recommendation for the frequency of disinfecting RV tanks. It seems that a tank in regular use with typical municipal water containing bleach will be good indefinitely. If you use something like unchlorinated well water you might want to disinfect at least every couple of months, but that is strictly a personal opinion. I have found that my RV water starts to stink after a couple of months when not used.

Beyond any doubt, sanitize the water water system. Legionella can be a really nasty disease and there have been reports of Legionella growing in hot water RV tanks. Doing the hot water side is a pain in most RVs. I first remove the plug anddrain my HW tank, use a spout to clear out any sediment, then I put the plug back in, fill with water containing bleach, soak and hour, then remove the plug to drain, and finally reinstall the plug and fill with regular water.

[Matt_Colie]

Doesn't anybody else use hydrogen peroxide?

We have for decades. Not the low density stuff for cuts, but the big number for hot tubs and such. Water tastes better when it is done.

Matt

[mbopp]

And remember - you must use real bleach, not the splashless type. Different chemical makeup.

[Lynnmor]

docsouce wrote:
Related Question. Do you guys drain and isolate your hot water tank or sanitize that too..

Of course, do the water heater as well. The hot and cold water comes out the same hole (faucet), so do it all.

[docsouce]

Related Question. Do you guys drain and isolate your hot water tank or sanitize that too..

[rvshrinker]

great, i liked the bleach in the hose idea and went with it. will rinse out tomorrow.

[SAR_Tracker]

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

[cavie]

1/4 to 15. Nothing else!!!!

[Dutch_12078]

The Northeastern info sheet seems to be for surface and bio-hazard decontamination where extended "soak time" is not very practical. For RV use, letting the weaker concentration sit for 3-4 hours is not usually an issue and cuts down on the difficulty of rinsing the taste out of the plumbing system.

[bob213]

I pour the bleach into my fresh water hose at the hose bib end. Hook it up and fill my FW tank. Hose is sanitized and so is tank. I've always gone with 1/4 cup to 15 gal.

[Monaramblee]

I pour bleach into the hose as much as the hose will hold then hook it up to the tap and fill the tank.

[Boon_Docker]

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?

[JesLookin]

We've been using 1/4 cup for every 15 gallons for many years. We've also been drinking water from our fresh water tank for many years. Works for us.

[midnightsadie]

do what royf says ,refill and flush all faucets, don,t forget the shower.