How Many Beds Can be Watered at One Time – What is Needed to Make the System Work Well?

Q.  I have a question concerning watering. How many beds can you tie together from one watering source and still water evenly? I plan on using one hose from the house to water the garden. I hope to build ten beds four feet wide and fifteen feet long. Will the Automated system work well with twenty pipes tied together?

A.  Yes, but how well depends on several factors, which I’ll explain in detail below  For your specific situation, unless you’re prepared to so some work, I recommend you buy the largest hose you can, so that it doesn’t reduce your flow too much.  You can tie the twenty beds all to a single header pipe, but then put valves at the beginning of each row, so you can water only one or two at a time, if necessary.  You will learn by trial and error how many will water properly with the volume and pressure you have.

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 1/2-acre 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 125 beds.

At what you would think is the other extreme are Jan & Gretchen Graf in Santa Clara, Utah (where the big flood happened this week – and their family farm is now a 30′ hole in the ground).  Their garden is still intact – the pictures are in the Photo section – and it is watered by gravity.  They collect water from a natural spring into 4-250 gallon tanks.  Those are connected in tandem with 1″ pipes, 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 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 the pictures 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 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 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 Schedule 200 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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