How To Build A Rain Water Collection System

Thinking about how you can build your own rain water collection system? Check out this DIY project where I built my own to collect rain water!

Ahhh look at this big tank! I’m so excited to not only finally get to this project but to also be able to share the process with you guys. This is a 30,000 gallon tank for my new rain water collection system.

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The system is also sometimes referred to as rain water harvesting and it’s when you put catch the rain and store it for later use. You can use the rain as is for non potable uses such as irrigation, laundry, flushing toilets….pretty much any use other than drinking.

However, you can very easily make the water potable so that it can be drinkable then run an entire household off of just harvested rain. I find the concept as well as the process so fascinating so let me show you my installation then at the end talk about the different reasons people consider and invest in a rain collection system. 

I want to say a big thank you to Lowes for sponsoring this video.

On a system this size, you can’t buy a tank like mine at your local Lowes. But you can buy all the plumbing, connections, and the guttering system.

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If you go with a storage tank my size, it will need to be professionally installed. I used the leading experts in rain water collection called Harvested Rain Solutions

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Regardless of how big or small the system is, the main components are the same. You need a way to collect rain off a surface. This is typically a rooftop and gutters.

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Then you need a container to put the rain in, this can be a small barrel or something larger like a tank.

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Then you need plumbing to connect the two. This can be something as simple as placing a down spout directly into a barrel, or something more complex like trenching and running pipe underground. 

When I built the shop I didn’t install gutters, so the first step in my process was to get gutters installed and have a way to collect the water. You can certainly do gutter installation yourself by buying the pieces and joining them together. But one huge advantage to going through a professional is they have the equipment to show up on site and custom make a seamless gutter for the length of your building. With it being one continuous length, instead of pieces coupled together, you’re gutters will have less weak points to possibly leak and cause trouble in the future. 

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I always dread looking for contractors to do work at my place. Vetting them is just time consuming. So for this job I took advantage of Lowes Installation Services. Lowes has a service to match home owners to independent contractors in their area for different jobs such as window install, deck building, fence installation and so many more categories.

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Having seamless gutters meant the team custom made two length of gutter about 74’ long and it was insanely cool to watch coming out of this tiny box truck….I called it the Mary Poppins handbag truck! haha.

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After the form was made, a few brackets were placed inside to not only give it bones to hold it’s shape but to also give a way to connect it to the building.

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It took three guys coordinating to lift it up into place, center it to the building, then start securing it.

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This whole process took less than two hours as I told them to leave off the downspouts. Those will be added later on.

Now that I had a way to collect the rain, now it was time to work on the other two main components, setting a tank, and running the plumbing. The team from Harvested Rain Solutions showed up with a trailer full of needed equipment and we got started. First was to prepare the site where the tank would be built. Tank placement is pretty important. I was thinking about placing it on the south side of my shop where it would be really close to the collection point, but I ended up moving it more into the woods on the east side which meant more trenching for plumbing but placed the tank below the level of my shop which will allow gravity to assist in the water moving into the tank from the gutters. 

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I’ll be mostly using the water for irrigation needs, not only around my shop but also around my house. So while a 30,000 gallon tank is large, it will get used surpassing quickly in my hot climate.

The tank needs a pad made from sand so Ron started flattening then building up a level location with dirt first then with sand.

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There is no bottom necessarily. The tank is built directly on this sand pad then a liner goes inside, so it’s important to get this really level. The site started off with about a 5” difference from one side to the next.

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After using the machine and an experienced eye to roughly get it level, the next step to fine tune it was to go around with a stick that has a laser on it (a transit) and find the high points and the low points. I never used a transit before but it was a very handy tool.

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I could set my laser stick in difference places around the pad and it would tell me if that area was high or low, then by how much. Then Ron would either move material in, or take it away depending on the answer. After going as far as he could with the machine, we repeated the same process but now used rakes. 

Ok that’s the pad done.

While we were doing that, the other two guys with Harvested Rain Solutions was working on the trenching.

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Now my area is mostly rock, but I’ve done a lot of dirt work to grade up to my building and these lines are only placed about 12” deep. And no, we don’t have a frost line where I’m at.

The guys did encounter some rock, but it was mostly dirt and they made great progress. A line needed to be trenched the entire length of the shop on both the front and the back side. Then another line to connect the two.

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This is so that when the gutters collect the rain, it will travel down the down spouts, then into plumbing in the ground. The water from the back will join water from the front then go into a single line that will be trenched over to the tank.

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The machine did most of the heavy lifting here then the guys went back with shovels to trench out a path for the down spouts to connect into the main lines.

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On my length of building, I’ll have three down spouts. One on either end then somewhere close to the middle. 

Once the trenches were dug, they started laying the plumbing. Long sections of high pressure rated PVC were connected together, starting at one end of the shop and going to the other. Every joint is primed and also glued together.

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The main pipe was cut at each one of the down spouts in order to add in a fitting to also tie them in. You can see these downspouts were placed carefully so they ended up at the center of my post. It’s small details like this that made me happy I went with experienced installers.

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Since there were three people on the crew, joining these together went very quickly. And keep in mind that all the work shown so far was done in a single day. It went very fast. But Ron here has done jobs by himself and developed a cool trick I wanted to show off for making a connection alone. After priming and gluing, he uses a strap hooked onto the end to pull on the joint of pipe while guiding it in. I love tricks like that. 

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So the size of PVC is determined by a few factors, which I think is intersting. My line starts off with using 3” PVC then goes up to 4”, then goes up to 6”. Because as water moves through the pipes the friction causes a built up pressure, it’s a call head loss. You can compensate or overcome that pressure by expanding the area it has to travel within. Other factors like the length of the run, if it’s down hill or uphill, and how much water is joining the system at different points are all considered. So while this is my set up, yours could require something different. 

Here is another good trick, for joining PVC….it was tricky getting the 6” 45 seated on the straight by just shoving it, so the guys dropped it into the ground and used a shovel against the bank and on the edge to compress it. Gotta love leverage!

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The rest of the PVC was placed in the trench all the way to the tank then next came back filling. Since I have a ton of rocks in my dirt, they use some clean fill I had on hand to put down directly on the pipe first. Not having rocks directly in contact with the pipe will drastically extend it’s life. Ron would use the bucket to drop in some, then I would spread it around slightly until the PVC was buried. Then he could very quickly use the skid steer to knock the rest over and grade it back like it was before. 

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With that tripping hazard covered back up, the guys installed the downspouts.

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If you already have metal downspouts then you could swap them out for PVC ones that can tie into the main lines. These are made from PVC but are painted to match the color of my facia and my gutters.

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Another thing you can get started with if you’re interested in collecting rain water but don’t want to invest in a system yet is to purchase a cute barrel like this one that you can find at Lowes, and place it directly under your downspout so the rain water from your gutters will fall directly into it. It comes with a spigot already and could be used for watering a small garden or tasks such as washing out paint brushes. 

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But lets go ahead and move on to the giant tank. This bundle here on the trailer is not only my 30,000 gallon tank but also all the fittings, pump, liner, and hardware to complete it! Ha, I think that’s nuts.

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And let me tell you, it did not take long to assemble it either. This is a Pioneer metal tank that will get a plastic liner inside of it.

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Note: there are a few choices on tank material out there….you can get plastic, metal, or even concrete. Pioneer has been making and improving tanks for this purpose for over 30 years so they know what works and they know what doesn’t. They know how to make it easy to assemble but also reliable to use.

The guys started building out the tank by joining the bottom panels together with vertical bolt strips. After the bottom layer was complete, the same process was repeated on the top. To kinda of give you a scale, the diameter of this tank is 26’ and it’s 7’ tall. No, it’s not a swimming pool, even though it’s large enough to be.

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With the body done, it was time to start building out the roof.

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Two trusses span the distance from one side to the other then the inside requires some prep work before the metal roofing panels go down.

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First plastic liner strips are placed over all the vertical bolt strips. This serves two purposes, one is to protect the liner from the hardware holding together the tank and two to keep the condensation on the inside of the tank instead of seeping collecting then moving to the outside. A condensation strip is also added along the entire top rim for the same purpose. 

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Ok and now roofing panels which are first secured to the two trusses. And if you’re going to ask if I’m going to be collecting water from this roof, Pioneer actually does make a tank that collects water from it’s own roof!

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At this point the material is only secure to the trusses, and to locate that outer rim of the tank the guys used this pretty clever jig made up of small PVC pipe. There are two joints that are the same length so that the bottom joint can be placed on the tanks lip which give the location on the top to the person running the drill. That’s a good one. 

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Once they secured all the way around the tank, next they used a pair of sheer cutters to trim all the pieces from square to round.

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Also a hatch is added in with a ladder that drops down. And heck yeah I got inside too, it was surprising light inside and really cool in my opinion. 

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The first thing to do inside is to lay down a geo-tech material which will prevent things from being able to grow up inside.

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Then the liner was unpackaged, unrolled, and installed (at this points it was a no shoe zone). This liner is plastic but it’s BPA-free and NSF-61 certified with embedded sanitized antimicrobial technology. And it’s worth noting that this Aqualiner is exclusive to Pioneer tanks.

It’s first attached to the bottom with the built in tabs, then all along the top.

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With my roof size (which is around 3700 sqft or 344 sqmeters for you metric watchers) it will take about 12” of rain to fill this tank. Once it’s full, the excess will go out what is known as the overflow line. This is located on the back of my tank so that when it is used, the water will go out into the woods which is also the lower point of the area. 

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Now to get the water out of the tank and back uphill, a small submergible pump is added to the inside of the tank and plumbed in.

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So looking at this shot here, the 6” line brings all the water in.

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The conduit line is power to power the pump…

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… and also gives me an outlet on the tank to utilize.

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Then this is the return line where the pump will push it back uphill to where I need it.

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A shut off valve is there as well as a hose bib. 

Then just one more line for the low pressure line which goes into a valve that will allow me to flush the pipes should I want to clean out any sediment from the lines. Or if we don’t get rain for a while, then the water in the lines will be stagnate and need to be flushed out so it doesn’t enter into the tank. This line was routed so it will hit two oaks I want to thrive. 

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Ok and just two more things, then I think that wraps up the system.

To prevent corrosion to the tank, two magnesium filled anode bags are buried around the tank. You’ll see this same concept used in water heater or even a buried propane tank. 

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Then to prevent erosion of the sand, a layer of gravel is added to the base and spread around. 

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It’s worth noting that you can get tanks in different colors, but I absolutely love the look and color of my tank.

Overall it took four days to get the system complete, which I find incredible considering how much trenching my layout required and how rocky my terrain is. 

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I’m sure a lot of people will ask why. Why consider a rain harvesting system? For one thing I love the concept of utilizing a resource that’s available so the idea of capturing the rain coming off the existing roof and using it for all my irrigation and other gray water needs, it’s very appealing. But then also considering the benefit of control… I have a well but they can dry up. Some wells have too hard of water, even with a softener. Or another common issue around here at least is there is too much sulfuric acid in it that the water is unusable without an aeration tank. 

Also if I turn it into potable water, I’ll have control over it’s quality. Even if you follow all the rules to protect your ground water, all the wells in an area can be contaminated by one neighbor not following the rules. Then for people who rely on City water, are reliant on that City’s water department to do correct/enough quality testing and you are constrained to their standards. If you have your own source, you can dictate the stand and quality checks.

Keep in mind that while my state doesn’t have laws against rain water collection, some do so be sure to check if you’re interested in setting one up. Remember that you can start small, like with a barrel under a downspout to water a garden or some grass, but if you’re going to get a larger system like this one then I 100% recommend finding a knowledge resource to plan the system out for you, even if you want to execute the work outside of the tank.

I gained so much insider knowledge from Harvested Rain Solutions because they have been doing it for so long, again they know what works and what to avoid. They get a big thumbs up from me if you’re in the Texas area, you can find them HERE

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I would love to hear your thoughts down below. Do you have a collection system? If so, what made you start collecting and what would you like to tell people thinking about getting a system? 

Also, check out these other videos on Rain Water Collection if you’d like to look more into it!

I hope you found this video helpful, I’ll see you soon. 

Things I Used in This Project:

Rain Water Collection
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One Response

  1. That’s a massive tank! I have 3 x 22,500 litre (5900 US gal) tanks (2 polypropylene, 1 cement) supplying my home needs. We don’t have town water, so these provide water for all our needs. Given the on-going drought here in Oz, I may have to put in a couple more later on.
    I’m interested in your comment about needing to treat the water for drinking – I’ve never known folk using tank water in Oz to purify water in normal use. It does goes through a 5 micron particulate filter before it reaches the taps (faucet).
    Is treating rainwater a legal thing in your state?

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