Monday, October 05, 2009

How many beds can I automatically water at the same time

Automated Watering Question. (Print and Save in Your Garden File)

The question of how many beds you can water with the "automated" system is very common and very important. How much you can water at one time is entirely dependent on the volume of water and the pressure with which it is delivered to your pipes. I'll give you some examples of extremes on both ends, and then try to give suggestions for your garden situation.

I have a 5 1/2 HP Honda gas-powered pump bring water to my garden in a 2" pipe, and I can water 20 to 25 30'-long beds at one time. The big pipe and strong pressure provide a large volume of water, thus allowing for fast watering of my garden of 125 beds.

At what you would think is the other extreme are Jan & Gretchen Graf in Santa Clara, Utah. Their garden has been watered by gravity. They collect water from a natural spring into 4-250 gallon tanks. Those are connected in tandem with 1" pipe, and a 1" pipe then goes to their garden. The top of the garden is only
about 3' below the bottom of the tanks, but with the fairly large pipe plus the pressure of the water in the tanks, they are able to water 4 30' rows at a time. And you will see from pictures in the Photos section of the that their garden is on blow-sand!

Meanwhile others who are on municipal water, supposedly with ample pressure, sometimes have a hard time watering two short beds without having the far ends of the rows suffer from lack of water. Four things usually contribute to this problem as follows:
1) they are using a garden hose (3/8" typically),
2) from a 1/2" hose faucet at the side of their house,
3) sometimes they mistakenly use 1/2" PVC pipes in the garden, and
4) some even use Schedule 40 pipe, which reduces the inside diameter even more.

Here's what I recommend you do to have the most volume and pressure for watering your garden:
1. Tap into your main water line, before it enters your house. This will be at least a 3/4" line, and often is 1", and the pressure will be unreduced by all the things going on in the house.

2. Use the same size PVC pipe between the main connection and your garden as the source pipe. This will assure that the same volume and pressure are available at the garden.

3. Continue with the same size pipe for plumbing between the beds, and do not go smaller than 3/4" pipe, even in the individual beds.

4. Use 200 PSI pipe in the beds, rather than Schedule 40. It will carry more water, it is much easier to drill the holes, and won't break your drill bit nearly as often. And if properly cared for will last 20-30 years.

5. Drill 3 holes every 4" at 45 degree angles using a #57 or #58 drill bit (see chapter 15 of the Gardening Course or look in the Files section of the Group site for details and graphic illustrations).

6. Do not make your beds much longer than 30', and certainly do not allow the far end of the bed to be higher than the water-source end. Water still hasn't learned to run up hill.

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