Collecting rain, an on-going experiment 24 Apr 2017
croyfamilyfarms rain

My neighbors must surely think that I am some kind of lunatic. Last spring I dug up half of the dying sod in the front yard and installed three 8x4 foot raised garden beds. Then, last fall, I started banging around with a few, bright blue, 55 gallon food-grade steel drums, in the car port, which I picked up to catch rainfall for my garden. In this post, I will detail my initial results using a home-brew system using these metal barrels.

While Sonoma county is not in drought, and hasn’t really been off target rainfall in recent years, the concept of catching and storing excess rainwater is one which appeals to my “sustainable gardener” ethos. Second to that, I strive to be cheap. Therefore, if I wanted to store water for use in the garden, I needed to find a way to put together a rain collection system for not a whole lot of money. I was able to acquire five of these blue barrels for zero dollars, quite the steal! Some researching online leads me to believe that these barrels may only hold up for two to five years depending on how rapidly they rust as the seasons come and go. This motivates another two criteria for my rain-collection system: simple and easily replaceable.

Fully connected rain barrel assembly

Hardware and Design

The priciest component of the setup is one which I expect to last effectively forever, the downspout adapters. These adapters are a thick plastic which should survive the elements, and are designed to reduce sending sediment, leaves, and other garbage down into my rain barrels, helping keep the barrels themselves simple. The cost of the adapters also factored into the design of the system. Since they were the most expensive component, I aimed to use as few downspouts as possible, and join barrels together into barrel systems which could be fed by a single downspout.

At the top of each barrel is a large threaded hole, roughly 2” in diameter, and a narrow 3/4” threaded hole. The 3/4” hole set the standard for sizing piping I used to connect everything together.

Initially I looked at purchasing and fitting a hand-pump to the larger 2” threaded hole. There are many hand-pump assemblies which can be purchased but the cost was prohibitive, from $30-50 for lower quality plastic pumps, up to $200 for durable metal hand-pumps.

I ended up drilling holes in the sidewall towards the bottom of each barrel large enough to insert a 3/4” threaded bushing, which a friend welded into place. Be careful when buying drill bits and always wear your safety glasses. I sheared the guide bit of one of the circular drill bits when creating the holes in the barrels and sent it flying across the workshop. The downside to working with steel drums is, as you might expect, steel is hard. I drilled the holes about 4-5” above the base of the barrel, to allow sediment to settle to the bottom without clogging the output valve.

When my friend finished with the barrels, I set about connecting the different barrel systems using the following hardware:

  • A few 10’ lengths of Sched 40 3/4” PVC pipe
  • 10 3/4” threaded-to-unthreaded PVC couplers
  • 5 threaded 3/4” plastic ball valves
  • 5 threaded 3/4” metal nipples
  • 2 unthreaded 3/4” plastic ball valves
  • 4 unthreaded 3/4” PVC plugs
  • 6 unthreaded 3/4” PVC T-fittings
  • 2 unthreaded 3/4” PVC 90° elbows
  • 2 large band clamps
  • PVC cement

I won’t dwell too much on the actual pipe fitting, since anybody with a measuring tape, hacksaw, and PVC pipe can measure out and connect pipes successfully. In my installation there are two “barrel systems,” connected to two separate downspouts. Each barrel system is connected together through the welded bushings (bottom piping, egress), and through the top 3/4” threaded hole (top pipeline, inlet).

The top piping allows water and air to be exchanged as the barrels fill. The bottom piping, which is itself independently valved for each barrel, allows equal filling of the barrel system and provides the spout for pouring water into a watering can.

The top piping is sealed with PVC cement, except for the inlet pipe which I may wish to change the length of later. The bottom piping is also sealed with PVC cement, except for the egress pipe which I may wish to change the length of later as well.

The water pressure for the system depends on the “height” of the water stored, so each barrel system is also raised on stacked cinder blocks. If you intend on raising water barrels, use cinder blocks, or cross-braced 4x4 pieces of wood because water is heavy. When considering water pressure with such a system, it is important to consider the top height of the water, not the height of your spigot. When the barrels are full, the water height is about 5’, but as the water level lowers, the pressure will drop accordingly. Since we’re only filling watering cans, instead of attaching hoses, this isn’t a concern for us. But if we were to attach a hose, it would be important that the hose-height during use remain below the top-height of the water in the barrels.

NOTE: My first design used brass valves, which look like a normal hose spigot, do not bother with these. They restrict the water flow, only use ball valves which, when turned, allow full use of the pipe diameter.

Cumulatively, once I experimented with the design, each system took no more than 30-45 minutes to assemble, not including curing time for the PVC cement.

Northerly rain barrel system

Mistakes Made

Of course, I made some mistakes in this experiment, many of which can be corrected as soon as the barrels are emptied for the season.

  • The downspout near the “south crop” receives the water from almost the entire backside of the roof and can fill in less than a couple hours during a steady rain storm. I want to add more capacity to that side of the house, which would likely require re-orienting the barrel system.
  • The barrels shouldn’t be sitting level but should slope slightly to allow air to push up through the exposed 3/4” threaded hole in the top where water enters. Currently, two of the barrels are leveled incorrectly and air gets trapped as the barrels fill with water. Unfortunately this air must be manually allowed out, by unscrewing the plug in the larger hole, in order for those barrels to fill entirely.
  • The downspout chosen for the “north crop” receives an adequate amount of output and also rapidly fills during a steady rain. But the water requirements for the north crop, which receives 12+ hours of sun during the summer, will far outpace supply. Although I am experimenting with better water conservation techniques for the north crop this summer such as: rice straw covering. oolas, and better timing for sporadic deep waterings, I will definitely serve the north crop the entire summer with water from the rain barrels.
  • The lip of the barrels should be shielded from the rain with a roof of some form, as water can collect in the tops of the barrels and sit stagnate for mosquitoes or rust.

After the 2017 season has depleted the rain barrels, I expect to spent a weekend inspecting, reconfiguring, and improving the system, but that will have to wait until all that heavy water is gone.


The most significant conclusion that I can draw from this experiment, and the data I have collected, is that my wife is incredibly tolerant to my nonsense. Bright blue 55-gallon steel drums aren’t the most inconspicuous addition to our yard, but it seems that my idiotic excitement at barrels full of water wins her over.

A more practical conclusion is that this project has been worth it, for no other reason than making me really consider my water budget for the season. I know for a fact that I will not reach September without depleting all 275 gallons of stored water. That’s okay, the water is there to be used, but I’m considering how much water different plants, soil types, and plot locations need.

Another conclusion to take away from the first year of this experiment is that cost is king. When I first scoped out rain barrels, some vendors in the area, including our local recycler, were charging $25-35 just for one barrel. I’m not aging fine wine in these barrels, I’m storing dirty water which rolled down off my roof. While I didn’t keep detailed receipts on this system, I estimate that I spent less than $100 total. Considering the cost of water, with this cheap of a system, I am still unlikely to break even unless the system is usable for 5+ years, which I doubt will happen. In spite of any financial incentive, the rain water is unfiltered, and also not chlorinated, which I expect to be better for the overall plant and soil health. Only time will tell however.

Although the system is small, it’s preventing 275 gallons of drinking water from being used for agriculture, and at the end of the day (for $100) that makes me feel good.