Rain Barrel for Garden Watering




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The purpose of this project is to collect rainwater into barrels to be used at a later time to water the garden/grass.


I spent a lot of time looking at different designs, how people built them from very easy setups (1 barrel) to multiple barrels (6+). The most important thing to note is that if you are going to use this for a garden, ensure that you get barrels that are food grade safe. Sometimes these barrels are used for chemicals which can kill your garden, or be absorbed and ingested (if you are growing food - like I am)


After obtaining your rain barrel(s) make sure that you take some time to clean it. Mine used to hold soy sauce (it stinks!)

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Step 1: Required Parts

Here are the parts that I used:

2 x 55 gallon food grade safe barrels

2 x 2" DWV MIP Adapter

2 x 2" DWV Street Elbow 90 degree Spigot x Hub

1 x 2" PVC Pipe 8 feet

2 x 2" PVC Tee (t section = 1 1/2" opening)

2 x 1-1/2" x 3/4" PVC Schedule 40 Bushing Spigot x FIPT

2 x 3/4" Short Galvanized Nipple

2 x 3/4" PVC Ball Valve

2 x 3/4" MPT x 3/4" MHT adapter with red valve

1 x Plumber putty

1 x 8 feet downspout extension

1 x downspout adapter with twist on (Connects downspout to extension)

Lots of extra garden bricks

Tools Used:


Utility knife

Drill bits


measuring tape

Step 2: Building the Valve

I chose to go with a 2 valve approach as I will be leaving one connected permanently to a hose, and wanted to have the option of filling up jugs, water guns, etc without having to disconnect the hose.

1. Screw the 3/4" MPT x MHT adapter into one end of the threaded valve.

2. Screw the 3/4" nipple into the other end of the threaded valve.

3. Screw the other end of the nipple into the 3/4" PVC Schedule 40 Bushing Spigot x FIPT

4. Insert the assembled parts into the 1 1/2" section of the PVC Tee.

5. Repeat steps 1-4 for second valve

6. Cut a piece of PVC tube

7. Connect valves together with PVC tube

Step 3: Connecting Valves and Barrels Together

1. unscrew one of the bung holes in each barrel

2. screw in DWV MIP Adapter into the bung hole

3. Connect elbow to the DWV MIP Adapter

4. Connect assembled valve piece (from previous step) to the elbows to join the barrels together

I connected this upside down to make it easier to see what it looks like when it is connected. Ideally, this will be done after placing the barrels in place.

Step 4: Building the Platform

There are lots of different ways to build a platform for these. You want to make sure that the barrels are high enough that gravity will do its magic to help keep the pressure up. My deck is already off the ground high enough that it is above my garden, however, I used some extra garden brick to hold them in place. I placed the bricks by the downspout and made sure that it was big enough to support the barrels and the weight of the water.

Note: This is not my final placement. I am planning on redoing my deck in the next couple of months or so, and will be redoing this part. My plan is to build a wooden platform and put up walls around it to hide the barrels (ideally will look like a small shed on my deck)

Step 5: Connecting Downspout to Barrels

1. Determine where you will place the hole in the barrel

- I did this by simply doing a mock up of how I would like it and then made a note of where to drill

2. Using a drill, drill a hole into the barrel

3. I did not have the right size bit, so I drilled a couple holes and used a utility knife to shave the edges to make it fit

4. Using some force and a screwdriver, I connected the downspout extension into the hole that I just drilled

5. Determined where I would cut into the downspout

6. Using the hacksaw, cut out a section of the downspout

7. Connect other end of extension to the downspout

8. Using zipties to secure extension to the downspout

Step 6: Overflow and Pressure Holes

It is important to consider what to do if you have too much water.

To overcome this, I drilled out a small hole on the side of the barrel that will act as an overflow. I will be connecting some tubing to this and running it away from the house to the grass.

Using a small drill bit, I drilled several small holes near the top of the barrels to allow air flow in and out to help with the pressure

Step 7: Water Test

This is a must do!

Once you have everything assembled, you want to make sure that there are no leaks, otherwise you will not benefit from this. I simply stuck a hose in the overflow hole and started to fill up the barrels. I did notice a small leak where one of the bung holes connects with the DWV MIP Adapter. To overcome this, I used plumbers putty around the hole.

After doing this, retested the water and it is all sealed now.

Step 8: Enjoy Free Water!

Now that everything is tested and connected and working properly I can now begin to collect rain to water my garden.

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    34 Discussions


    5 months ago

    You probably already know, but the overflow might give you problems: too small, not piped to drain (extremely bad for house). You might have to go the full gutter size, and back to the downspout storm connection. The water can even back-up in the supply line.

    Wonder if you could get by with: put downspout the way it was. Then put a 1" threaded fitting in the side (use gaskets and 1" electrical nut). Then, a scoop needs to be made; get another threaded fitting and cut/form it to make a scoop. This may not work because of the tendency of water flowing at downspout wall, but I'd guess there is enough splashing to have water fall through the center for the scoop to pick up. As is, those barrels might fill/top-off in a matter of minutes.

    Just some thoughts.

    4 replies

    Reply 5 months ago

    Yeah I'm going to re think this. We just had 3 straight days of rain and this filled up in no time. As stated I'm redoing my deck so how it flows away from the house will he slightly different


    Reply 5 months ago

    I have a downspout diverter valve. I think I got it on e-Bay. It works well, but it is manual.

    I recently added an L-bracket with a pull-string (and eyelets) to ease the switchover. I can then give it time for first-flush and then switch over to fill the container. Automation can go anywhere from here, but it would be quite involved. You may want to arrange yours to pull it closed.

    Anyway, good luck.


    Reply 5 months ago

    That is really smart! I may look into doing something like that using automation. I think it would be easy to automate using a float valve (like a toliet) and once it reaches a certain level, switch the overflow to go back down the downspout. May look into that one. Great idea!


    Reply 5 months ago

    Appreciate the feedback :)

    We have had a lot of rain over the last couple weeks, and the overflow is working perfectly! There was only 1 night where it was really bad and I had water coming out of the air holes. I will likely be cutting a bigger hole for overflow to help.

    The overflow that is there will be connected with a hose that will lead away from the house (Where the water currently overflows is far enough away from the house - and there is a slant away from the house) that this will not be an issue. Nevertheless, I want to overflow to run further away (eventually overflow will lead to another garden/tree).

    When I redo my deck, I will be changing how the barrels connect with the downspout. I will likely be creating a overflow that will feed back into the downspout.


    5 months ago

    I feel your design is very revolutionary. If you had inspiration from others, please share! In my area it rains for only a short time each year, so storage can be an issue (like, where do I put a tank that is 10' dia. and 8-10' high?). Mounting the barrels physically in series, but hydraulically in parallel would fix that for many, i.m.o.

    I really like the inverted barrel with the dual valves. It eliminates bulkhead fittings and the cross-piping easily shares storage capacity across several barrels and doubles as a bottom drain for seasonal cleaning. The vent holes in your design are needed (and the small size acts as a bug/debris filter), but my preference would be for a single point of overflow on the first barrel and directed somewhere easy to manage in that event (like the pressure/water blow-off on a traditional water heater).

    How often does it rain in your locale? You have pre-screening at the rain gutters, but you may benefit from a diverter between the downspout and the barrel so the dust and stuff that collects on the roof between rains that washes off in the first few minutes of rain doesn't go into the barrels (less maintenance and water quality issues over time).

    Also, I would like to echo dleland71's caution about the foundation. For each barrel I would plan for a 200% dead load, which (if my math is good) will be in the neighborhood of 280 - 300 lbs./sq.ft. Some references on DIY aquariums may be a good source for additional information.

    Again, good job!

    1 reply

    Reply 5 months ago

    Thanks! Like I said I looked at tons of different design from a lot of different people! I thank the whole rain barrel community lol

    I do have an overflow that is hidden from in the pictures. It is in the second barrel. After installing this, we had 3 days of pure rain and it filled up very quickly and the overflow worked like a charm.

    I hear what you are saying with the filter/diverter. Any dust or fine debris will make it to the barrels. At this point, it should be very small and come out with the water. I am only using this to provide water to my garden and lawn (not drinking) so it is okay for a little bit to make it in. I am more concerned with the big stuff (leaves etc) as they can plug up the system.

    I live in Ontario, Canada. We do get a good amount of rain, but I wouldn't say it rains all the time or anything like that. We do get some dry times here and there

    As it turns out I am also in the aquarium/paludarium hobby and very familir with this weight. As I said early, I will be tackling the weight issue when I redo the deck. :)


    5 months ago

    Also keep in mind, depending on your location, mosquitos like to lay their eggs in standing water. A filter, or at least a screen small enough to keep them getting through at the downspout is a must for open water collection.


    5 months ago

    When i did something similar in scotland, what i found was that if the downspout goes straight into the barrel any dirt, leaves or moss on the roof are washed into the barrel and accumulate in bottom of the the barrel in the form of sludge. so best to have some sort of filter to catch this.

    1 reply

    Reply 5 months ago

    I have this happening on the eavesdrop to prevent this :)


    5 months ago

    I'm puzzled by this setup.
    I collect rainwater on a largish scale, so much so that the mains water supplier (utility) thinks I fiddle the meter. The only thing I don't do with it is drink it.
    Where did your rainwater run to before? Was it to a soakaway or just over the ground? In UK, it is illegal to connect surface water to foul sewers so that just leaves soakaways. Letting it run away uncontrolled is a bad idea.
    Sometimes people use rainwater diverters that fit in the downpipe. These might work if you have a slate or metal roof with very little debris, but if you have concrete tiles, the moss, lichen and sand that comes off these tiles will soon block a diverter.
    If I want clean rainwater, I have a small gravel and fishpond prefilter between the downpipe and the storage tanks. Any overflow goes back down the remaining connection to the soakaway, but only after filtering. If you let all the debris go to the soakaway, you will soon be in trouble with blockages.
    If I just want water for plants, then all the downpipe water (no diverters) goes into the tank. The tank has a PVC 38-mm tank connector and waste pipe that connects to the original soakaway.
    In the wastewater business, which I was, there was a lot of floating debris which couldn't go down any overflows. The solution is easy. Instead of just a plain tank connector at the overflow level, there was an open "T" in whatever size pipework - imagine a T rotated through 90 degrees - the original vertical goes to the tank connector and the horizontal has one opening above the water level and the other below - all water going to overflow is drawn from below the surface. The tank now acts just like a giant gully pot. It gets cleaned once a year which is a lot easier than digging out a blocked soakaway.
    So far, since collecting rainwater, I have saved over 100-tonnes of scarce drinking water.
    Rainwater is great for any washing, soft water, and why use drinking water to flush the lavvy?

    1 reply

    Reply 5 months ago

    The rain water before this just simply went down the downspout and under the deck away from the house. It would simply just soak into the ground.I do not plan on having this being uncontrolled. Once I redo my deck, the overflow will go into a tube that will run out the back of my yard. I don't have to worry about debris, as I do have a screen preventing the debris from getting into the barrels.


    5 months ago

    Something that should probably be noted (and perhaps this goes without saying, in which case disregard this comment) is that collecting rainwater is not legal in all locales. Many of the restrictions in the United States allow for modest personal setups such as this, but Colorado, for instance, has zero tolerance for any form of rainwater collection.

    5 replies

    Reply 5 months ago

    Thanks for the correction. My reference was published just prior to that bill’s passage in 2016. Sometimes I forget what year we’re in and how quickly policy can change.


    Reply 5 months ago

    Really, illegal! regulated! First this nation was shared by nomadic indians. Then the Christian White Men came with their salves and economic system and property rights (land grants from Kings of distant lands) - jeeze, talk about "into each life a little rain must fall . . ."
    Are these Democratic legislators or Republican?
    Think about it - why are folks collecting rainwater? to irrigate, right? So, they are temporarily impeding the runoff, then letting it go a bit at a time.
    Gee John Denver made it sound so nice "Colorado rocky mountain high" Oi Vey!


    Reply 5 months ago

    You are correct. It is not legal everywhere and you should check your local laws. Where I live (Canada) it is perfectly legal to do it


    Reply 5 months ago

    Here in Oregon, you can only collect what falls on your roof. Hopefully the people in Colorado will wake up and make changes to their rain water collection laws...


    Question 5 months ago

    Really cool project and I know my wife would love to have one. Only question I have, and it is probably a dumb one so please forgive me; but I only see your downspout going into on barrel. How are you filling up the second barrel?

    1 answer

    Answer 5 months ago

    The barrels are connected by the black pipe underneath. As water seeks its own level, the black pipe will fill first. Then, once the pipe is full, any additional water will be divided (equally!) between the respective barrels. Now, the 'first' barrel will initially have a somewhat greater portion of the incoming water - but they will balance out. The 'lag will be dependent pon the relative diameters of the intake and crosser pipes.