Rainwater collection is not just for your garden – it’s also great for drinking. But you want to make sure it’s safe, and how you store your rainwater is an important part of that.
How long can you store rainwater for drinking? Rainwater can be stored from anywhere between one week and indefinitely. The more consideration you put into your storage system – using the right materials, preventing algae and mosquitos – the longer your rainwater’s shelf-life.
All the thought you put into rainwater harvesting and storage becomes much more important when you intend to drink it. But maintaining a great storage system for your water isn’t hard if you cross all your t’s and dot your i’s.
Safe Storage of Rainwater for Drinking
I’d like to mention that we’re not talking here about the potability of the water immediately after you’ve harvested it; that’s a whole different conversation. Properly storing your rainwater can however limit additional contaminants to your harvest. The main factors in rainwater shelf-life:
- materials of your tank
- preventing growth
Have you ever noticed the expiration dates on plastic water bottles? That’s not an expiration date for the water, but for the bottle. It seems like a no-brainer, but you don’t want to store your rainwater in anything that’s going to break down quickly or leech chemicals into your water supply – if you’re choosing plastic, go for BPA-free #1, #2, or #4 plastic.
Plastic is commonly used in collection barrels you buy in the store, but here are some other materials you may want to consider:
- Concrete: A sturdy material, and some types can neutralize the natural acidity of rainwater.
- Wood: These days, this might be a more expensive option and if it begins to dry out, it can leak.
- Fiberglass: Rigid but lightweight. However, be aware of any damage as the fibers are small and sharp.
- Metal: Corrugated metal is a common material for water collection tanks because it is relatively inexpensive and sturdy. Steel and other metals are a more expensive alternative.
(You can find more details about tank materials on this Texas A&M webpage.)
There are two types of growth you need to prevent: plants (mainly algae) and mosquitos.
- Algae: One easy way of preventing algae growth is to limit the amount of light that enters the tank. You can do this by burying your storage system, painting it a dark color (black, brown, or even blue), or putting it in a dark location.
You can also add an appropriate amount of chlorine or iodine to the water; this will keep the algae at bay as well as kill off waterborne diseases like giardia.
- Mosquitos: Obviously you don’t want to drink mosquitos or their larvae, but you (and your neighbors) are not going to be thrilled with an extra breeding ground in your backyard.
One way I’ve found is to add a little bit of vegetable oil to the rainwater, just enough to coat the surface – maybe less than a tablespoon! Since it floats to the top, if you’re pulling water from the bottom for you to use, the oil will not be in the water you wake, but it will stop the mosquitos from breeding.
An important thing to remember is that these two water pests have different growing conditions, so don’t assume what works for one will work for the other.
Rotating Your Water
Think about some time you’ve been walking in a forest, and you saw some stagnant pond coated in scum and buzzing with mosquitos. I’m positive you didn’t even want to touch it, let alone drink it. So keep your rainwater moving!
If you’re using your water frequently, all these problems become simpler. Adding water and taking some out will help a little, and you can always empty your tank completely to clean the inside well with bleach; this will definitely help kill off anything growing in there. Some websites recommend doing this once a week, but if you take the necessary precautions, you can certainly go much longer.
If you’re planning on keeping your water as part of an emergency kit, you should absolutely filter and purify it before you put it into storage. Remove whatever chemicals and microbial life are in it and then put it in a sterilized long-lasting container.
While this should be sufficient to ensure your water is safe for you to use if you ever need it, there’s also nothing wrong with occasionally rotating this water out and replacing it for your peace of mind.
How Do I Get a Rainwater Storage Tank?
If you’re looking to buy a prefabricated tank, you can easily find them at your local hardware or garden supply store or online. Amazon has tons of options, in a variety of sizes, prices, and materials, from a collapsible tank, to a plastic barrel, to a terracotta urn with built-in planter, just to name a few.
There is also, of course, the option to go DIY. Again, you don’t want to take any old container lying around your garage, but with the right materials you can create a container that fits your specific needs.
Is Rainwater Even Safe to Drink?
Of course! – if you take the necessary precautions. You wouldn’t lick your roof, would you? Well, if that’s where you’re collecting rainwater from, that’s kind of what you’re doing. The CDC has a lot to say about it. According to their information, rainwater can include:
- Smoke, soot, and dust absorbed in the air before the rain makes landfall
- Roofing materials like asbestos and metals like copper and lead
- Natural contaminants, like bird poop, insects, pollen, and bacteria
Long story short, you need to purify and filter your rainwater before you drink it.
By the time water reaches your tap from the water department, it’s been through some of the same processes. The only difference is now you’re in charge of it; you’re cutting out the middleman.
That’s probably the main reason while in some areas, it’s actually illegal to collect your own rainwater, so you’ll need to check with your local authorities to make sure this is all above board. However, more and more places are lifting these restrictions as water conservation becomes a more global issue.
Now that you know all about storing water, you may be realizing that you don’t know all that much about how to harvest it in the first place.
The most common method is rerouting the runoff from your roof into a barrel or a tank. Sometimes this is an open spout or chain that pours into the barrel – an easy alteration to your current rain gutters. More advanced collection uses a fully closed system with a spout that is attached to the tank with no gaps. This would require often more specialized tools and materials.
Another method is to collect water from the ground rather than your roof. The benefit of this method is it catches more water than the aboveground system. With the collection pipes underground, you can harvest the water from multiple gutters as well as water flowing on the ground or down a hillside.
In this way, water collection not only offsets your water cost and raises your awareness to your personal water usage, but can also reroute potential flooding from your house. If you have water seeping into your basement on one side of your house, consider laying a catchment pipe along that side – not only will you no longer have flooding, but that once destructive flow can be used to your benefit!
For more information on rainwater collection, I have found this article from a Texan water collection company to be particularly detail