How To Collect Rainwater & Figure Out How Much Water You Need To Survive
One of the most important journeys you will go on in your off grid journey is how to get water. When you arrive to your new land it’s probably the first (or at least second) thing you think about. And for good reason! We were no different. Even before we arrived at our land, we were discussing what we would do to get water. There are a few different options, but that’s a topic for another time. For now we want to talk about what we settled on, and that is rainwater collection.
What Is Rainwater Collection
Rainwater collection is simply collecting rain whenever it falls and storing it to be used whenever you need it. There is a common misconception that collecting rainwater is illegal. This is not true. There are no states in the United States where it is illegal to collect rainwater. Colorado and Utah are the states that have the most regulations, but collection is not illegal. As with everything check with your state/city/county to find out if there are any rainwater collection laws or rules.
What Vessel Should You Collect Rainwater In
There are a few different vessels to use to collect rainwater, but in general, any food grade container that will hold water can be used. This means you could use a 5 gallon bucket or even a stock pot. If you took one of these and just set them outside when it rains, then you would have collected rainwater. But if you are living off grid, you are going to want a lot more than 5 gallons.
You can definitely find a vessel at a big box store for collecting rainwater, but these are usually too small for supplying your with your entire water needs, they are not easily manipulated, and they are also very expensive.
The most common vessel is probably what people call a “rain barrel”. This is just a 55 gallon barrel that is food safe and they usually are white or blue. These are great if you just want a couple barrels to water your garden.
If you need more than that you will want something ever larger like an IBC tote which is usually 275-300 gallons. You can usually find these used relatively inexpensively . The one thing you have to be careful about is only buying IBC totes that they are food grade. A lot of IBC totes are used for chemicals and toxic liquids, and you would certainly not want to use one of those to store your water.
If you want even more space in your vessel, you might want a storage tank that could hold 500-5000 gallons. These are rather expensive unless you can find them used, but used containers that size are hard to find.
There are vessels that exist to contain even as much as 20,000 gallons but these are very expensive and usually made out of galvanized steel. If galvanized steel is something that is interesting to you (over plastic storage tanks) you could even use a stock tank. Stock tanks come in many different sizes. We have one that holds about 100 gallons of water that we collect water in and we mostly use it for watering plants. Of course the issue with the stock tanks is the water is out in the open and not covered. Depending on what you are using your rainwater for, this may or may not be an issue.
Isn’t rain acidic?
Rain can be more acidic in different parts of the world, but for the most part it is safe to drink when filtered. To figure out the pH of your water, you can purchase a water testing kit. This meter is easy to use and can give you a pH reading very quickly. If your rainwater is too acidic, you can change the pH level. Just a tiny amount of baking soda will bring the pH back into a desirable range. You need about 1/4 tsp. baking soda per 1 gallon of water. If you filter your drinking and cooking water through something like a Berkey filter, it would be best to treat your water as you use it. If you treat your whole tanks, more rain will come in and mess the pH up all over again. If you are going to filter your entire system, you will have to design your system in a way that will allow for accurate pH testing and altering.
I’m going to be honest…. we do not adjust our pH on our rainwater right now. This is something that we will likely do in the future once we have a more completed system. But for now our rainwater collection system is simple and was quick and easy to set up.
How Much Water Do I Need To Collect?
Figuring out how much water you use on a regular basis and how much you will need to store requires a little math, but you’ve got to figure it out. If you are on the grid now, you can check your water bill and see how many gallons you use per month. However, if you are like us, you will likely change your water habits once you start supplying your own water. To get a better idea of where you could make some changes, make a list of all the things you do that use water in a week. For us the list looks a little like this (the amount of gallons what we use in a week):
Drinking (Humans & Dogs)- 10 gallons
Cooking- 2 gallons
Washing Dishes- 12 gallons
Washing Clothes- 60 gallons
Showering- 68 gallons
Flushing the Toilet- 150 gallons
Watering Farm Animals- 5 gallons
Watering Plants- SO MANY gallons, probably 50 gallons/week
After this list is made, you’ll need to estimate how much each of these things use and how many times you do it per day. A quick internet search will help you find things out like “how many gallons does a toilet flush use?” If you recently installed a toilet, you may even be able to find out exactly how many gallons your particular model uses. But even if this isn’t the case, you can still search the internet for a simple estimate. Seeing how much water is used to flush the toilet might make a compost toilet look like a better option than a flush toilet. It’s pretty surprising how much water is used just to flush the toilet.
After you figure out how much you use each item, you can figure out how much water you would be using in one week. Then multiply that by 52 to see how much water you will require in one year. For us this number comes to 18,564 gallons per year. We also plan to fill up our stock tank pool this year and that is 1100 gallons. So we will add that to the total: 19,664 gallons. Because we would like to play it safe, we will round this up to 24,000 gallons. So our goal is to collect 24,000 gallons of water over a year.
The next internet search you will need to do is how much rainfall your area receives in one year. Here we receive around 55 inches per year.
The amount of rainwater you are able to collect is based on how much roof space you have and how much it rains where you live. 1 sq. ft. of roof space collects around .55 gallons per inch of rain. The equation is pretty simple.
Roof sq. ft. x .55 x Inches of rain per year
If you know how much roof space you have, you just plug your numbers into the equation. We don’t have all our roofs built that we will collect rainwater off, so for now we have 676 sq. ft. of roof space.
676 x .55 x 55 = 20,449
This shows that the most rain we could collect with the roof space we have is only 20,449 gallons per year. Since we need more than that, we know we will need more roof space. If I work out the equation backwards, I know that we need at least 800 sq. ft. of roof space to collect what we need.
Assuming we had the roof space that we need to collect all the water we need, we now need to figure out how much storage space we need. We don’t want to run out of water at the end of every month, we will want to have containers to hold at least 2 months worth.
24,000 gallons ÷ 12 months = 2,000 gallons/ month
Ideally, with all of this information, we would have vessels that held 4000 gallons of water. But we could also get away with anything between 2000-4000 gallons. We chose to use IBC totes because they are easily accessible and we can add on to our system very easily. Since this is the case we will need 7-8 IBC totes to hold 2000 gallons at a time, but if we want to store 4000 gallons we will need 14-15 totes.
A few notes about collecting rainwater if you live in a dry climate. As previously noted we get 55 inches of rain per year which is a lot and significantly more than the national average of 30.28 inches per year. Living in an area with this much rain gives us a lot more flexibility than someone who lives in the desert. For comparison, everyone thinks that Seattle is such a rainy city but they get an average of 37 inches of rain per year. We practically live in a rain forest! I’m rambling on to get to the point that you CAN collect rainwater even if you live in a dry climate. You will need as large of a rain catchment area as possible and you will need to contain as much rain as possible for the many months you could go without rain. Check out Homesteadeconmoics on YouTube. He lives in Arizona and collects 90% of his family’s water. He has a lot of unique ways of catching as much rainwater as possible. Collecting rainwater in a desert area vs a very wet climate like where we live is a bigger investment. However, in comparison drilling a well is very expensive. You could attempt to drill a well, spend thousands and end up not finding water.
Okay, this is a lot of information to take in. I was originally going to tell you all about our simple rainwater system setup but then I thought maybe I should explain some rainwater basics first. I will have another blog post about how we set up a VERY simple rainwater system soon, so stay tuned!
