Sanitize water tanks

Hi.  We are living off grid and now have 3 water tanks that need to be sanitized.  PROBLEM:   our daughter is severely allergic to chlorine and can't even wah her hands with chlorinated water without having breathing issues.  What are some reliable alternatives to kill bacteria and not our daughter? Any ideas would be welcome.....

UV light is really good at sanitizing water. Out on the market are ultra violet water sanitizers that are a tube with a UV light inside it, and at each end are threaded fittings for plumbing. Water goes in one side passing over the light and comes out the other end sanitized. While this doesn't solve sanitizing the entire tank, it can provide sanitized water for point of use as needed.

We drain and clean our water storage tanks with vinegar a couple times a year.   Ours are not more than 100 gallons each so its not too big a deal for us.

How big are your tanks? What sort of access to the interior is available? And, what do you suspect your tanks are contaminated with?

Offhand, if you have access to the interior of an empty tank, I think hydrogen peroxide in a sprayer could be an option. Most sterilizing processes require a substantial wet contact time, though. It may take more than one application.

Our tanks are 1300 gallons, 100 gallons and 250 gallons.  The big one has an access port so we can get inside of it.  The others don't.  The tanks haven't been used in about 4 years, so anything could be growing in them.  We don't want to take chances.  

UV light may be an option.

Douglas Alpenstock wrote:Offhand, if you have access to the interior of an empty tank, I think hydrogen peroxide in a sprayer could be an option. Most sterilizing processes require a substantial wet contact time, though. It may take more than one application.

This is something I was going to suggest, but again, if you have access to it. If you don't have access, then i think you need to have something diluted in water. everything i've seen about using vinegar (admittedly, it's for RV tanks) says 1:1 solution, which is a lot of vinegar.

FWIW, chlorine used for sterilizing doesn't linger, it evaporates off. A tank that is sterilized can be drained, rinsed/filled and drained with little residual chlorine left. The experience is quite different from municipal tap water, which by design has lingering forms of chlorine at specific concentrations in the pipe network.

Sorry if I was not clear about sanitizing our water storage tanks.
We use full strength vinegar, we spray inside the tanks and shake them up if possible.
let sit for a while, maybe up to an hour or two. Wipe insides a little then rinse out.  Does not take more than a gallon or two.
We also make vinegar year round, very easy and very cheap.  We use it for most of our cleaning around the homestead.

You can use what cheese-making plants use - 35% hydrogen peroxide.  Breaks down into water. Hazardous to use as you don't want any to get on your skin at that concentration, but absolutely safe after it's done its work.

I think from my experience is that large water tanks filled with rainwater and using basic first flush units and filters for leaves will suffice.
You need at least 20,000L of water and with that volume it becomes self cleaning, not requiring any treatment at all.
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