greentheo

After recently completing my Solar heater, it was time to embark on a new project... rain collection and redistribution for my garden.

Colorado is a wonderful place to live, but it can also be quite arid and moisture free.  Thus, to grow many of the vegetables we know and love to eat, plenty of outside water is commonly used.  But it sure can get expensive!  Last summer my bill averaged $50-$75/month just for water![1]

So how much water can you collect from rain and snow anyway?

For every 1000 sq. ft of roof on your house one can collect:

• 144 sq. inch / sq. ft. X 1000 sq. ft. = 144,000 sq. inches
• 1 inch of rain X 144,000 sq. inches = 144,000 cubic inches of water
•  144,000 X 0.004 gallons / cubic inch = 576 gallons

On average, Boulder, Colorado get's about 19 inches of moisture... and thus my 1000 sq. ft roof can collect with it's pre existing gutter, about 11,000 gallons of water.

How much is practical to store for your garden?

While this depends on your particular garden, the answer is that it's practical to store as much wat as you'll reasonably use over a week's time.  For a more practical calculation consider the rule of thumb that your plants want to get about 1 inch of rain per week.

My garden is 150 sq. ft (and growing) so I want to have 150*144*1*.004 = 86 gallons available on demand.  Luckily I happen to have 3X55 gallon drums on hand giving me 165 gallons, 82.5 for watering... and 82.5 for storing for the next week.

So the rule of thumb turns out to be: 1/2 gallon per square foot of garden = 1 inch of water/week.

Other design considerations

I currently am cultivating ~150 sq. ft.  But I'd like to add another 50-100 sq. ft. so I'd also like to be able to store my rain holding capacity appropriately.  By the above calculation I know that every 50 sq. ft is properly served by a 55 gallon drum.  Therefore the design of the rain storage and redistribution system should accomodate the adding of future drums.

Materials

• 3 - 55 gallon drums - food grade ~ $20/each, free if you know where to look or have nice friends
• 2 - 4' sections of flexible pipe ~ $5, or free if you look around
• 1 - 3/4" male threaded PVC bung type fitting ~ $0.50
• 1 - 3/4" female thread to garden hose thread fitting ~ $0.50
• 1 - garden hose on off valve ~ $2
• 1 - male garden hose to male garden hose adapter ~ $5
• 1 - (optional) - automatic water metering valve ~ $15
• 1 - garden hose to dripline attachment, or , drip hose ~ $1, $10
• 1 - dripline with drip buttons at .5 gph rating  ~ $5

Total: as little as $15, as much as $95
The finished design

Here we have 3 food grade 55 gallon plastic drums.   The black pipe runing between the three barrels (all the way to the bottom of either barrel) is for auto-siphoning between the barrels.  When the barrel at the end of the spout fills, the water is automatically siphoned to the the second barrel... when both are full, the water siphons to the third.. etc.  Furthermore, once the whole system is full, any change in level in one barrel is distributed evenly to all the rest provided that the siphon is not broken.

Step 1 - Site the area for storage and collection

Take a look around your proposed garden and water storing area. The best areas are ones that:

• can easily collect water from the gutters of your roof
• are mostly out of the way
• are closer to your garden
• are more elevated than your garden

Step 2 - Put a bung in the barrel

Drill a one inch hole in the last barrel near the bottom.  Water leaves the system here.

Step 3 - Insert the male threaded PVC bung

Step 4 - Using silicon caulk, make a bead around the outside of the bung and let it dry.  Make sure that the femail pvc thread to garden hose thread can screw on first.

Step 5 - Screw on the female PVC to garden hose adapter.. the silicon caulk should act like a custom molded washer or gasket preventing leaking.

Step 6 - Screw in the stop valve, the male to male adapter and the water meter (if you'd like)

Step 7  - Screw on the drip line or drip hose.

Step 8 - Drill 1 inch hole on the both sides near the top of any of the intermediate barrels.  Should be near the top, but not at the top.  An auto-siphon only works when the level of the water threatens to rise above the siphon point.

Step 9 - Drill 1, 1 inch hole at the top of the entrance and exit barrels.

Step 10 - Move barrels to site.

Step 11 - Insert auto-siphon tubes between barrels. Make sure it goes down as far as possible into each barrel.

Step 12 - Attach entrance barrel to gutter and wait for rain!

Summary

A rain barrel is a great addition to any garden.  Not only do they lower the cost of gardening but they also help out your municipal water district by lowering the demand for water.  They can be cheap and easy to build in such a way that they mostly act autonomously, distributing water slowly to your garden at a preset drip rate.

Now if only it would rain or snow around here!

1. And I know I wasn't over watering because I only ran the sprinkler system inthe backyard for 5 minutes every day in the morning... and that's it. [↩]