Using Irrigation Water in the Automated PVC Watering System

Q. Which book of the Mittleider gardening books gives the best detailed instructions on using irrigation water with grow beds? I have seen some pdf files on basic set up for grow beds, the last thing i want to be doing is unplugging clogged holes several hours a week. Can irrigation water be used in all circumstances, do you need a certain amount of psi?

A. Probably what follows is more detailed than in the books.

Irrigation water can be used in the automated PVC watering system, but care must be taken to filter the water before it goes into the pipes. The stronger your pressure, the less problems you’ll have and the faster you can water your garden, but we sometimes water with only gravity pressure.

In addition to sand, etc. plugging the pipes there is the risk of small weed seeds getting into the garden. For this reason it is a good idea to filter irrigation water if possible, even when using it directly on your beds or boxes.

In the Foundation’s Zoo garden in SLC, Utah we filter the water from the creek right as it enters the 2″ flexible hose from which our Honda 5.5 hp pump sends it into the garden. We use three levels of filtering, very coarse to stop rocks, etc., medium to stop pebbles, and nylon hose for the finer particles.

Regardless of our best efforts some things still get through. In the beginning I kept a couple of awls handy and (too often) would resort to reaming out the holes. With over 100 beds you can imagine this could be a BIG job!

We soon discovered that you can open the end of the pipe for a few seconds, close the end, then tap on the pipe with a hoe or rake handle while the water is on. This almost always clears the obstructions. And it is a good idea to open the end a second time AFTER tapping on the pipe, thus letting the debris you’ve dislodged wash out also.

Eliminate the Drudgery, Save Water, and Water More Efficiently!

Automating your watering system takes much of the drudgery out of the gardening experience.  It also assures more efficient use of the precious water, and does a better job of watering every plant evenly.  I highly recommend it!

This process is covered, with illustrations in the Mittleider Gardening Course, chapter 15, which is available at  That chapter is also available free in the Store section, and it’s included in the Files section of the MittleiderMethodGardening Group on YahooGroups.  Following is a recap of the procedures. 

The first thing to do is to measure, mark, and stake the garden, followed by trenching and installing the PVC feeder lines.

First, determine what size pipe you can use.  If the source is only a hose bib, then 3/4″ pipe is all you need.  Watering will be much faster if you have access to a 1″ or larger water source.  Measure the distance from the main water source to the head of the farthest bed, as you will want a header-pipe that long. 

Buy PVC pipe as large as the pipe from the water source, or 3/4″, whichever is larger.

Your trench for the header pipe should be 9″ deep and very close to the beds, so the risers come up only a couple of inches or so from the end stakes at the center of the bed.

Buy slip/slip/thread T’s for risers to each bed, with the threaded T being 3/4″, and the slip sides matching the header pipe.  Cut your header pipe so the T’s are at the center of each bed, then glue them with the T straight up.

To make risers you’ll need one of the following for each bed:
1) 12″-long 3/4 Schedule-200 pipe,
2) 3/4″ slip/threaded female/male connector (to go into the T from the header-pipe),
3) 3/4″ slip/threaded elbow,
4) 2″ threaded bib,
5) plastic threaded ball-valve,
6) Schedule 200 PVC pipe, cut to the length of your bed or box,
7) 3/4″slip/threaded female/male connector (for far end of pipe),
8) 3/4″ threaded end cap. 

To drill holes in your pipes for watering, you need some #57 drill bits and a drill.  To make a jig for marking the pipe, you need a 6″-long piece of 2″ X 4″ board, a pencil, and a drill bit the same size as the pencil. 

Cut a square piece out of the long side of the board at the middle, so the opening fits the pipe snugly, then drill a hole from the top down to the middle of that square opening.  Inserting the pencil into the hole, pull the board along the stationary pipe to mark a straight line.  Then turn the pipe 45 degrees and repeat the line, and another 45 degrees and repeat again.

Stretch a tape measure along the length of the 20′ length of PVC pipe.  Mark a line every 4″ that intersects the 3 lines already on the pipe.  Drill a hole where the lines intersect – 3 holes every 4″ for the length of each pipe.  Thats a lot of holes, but don’t let it scare you.  They go very fast once you get started, and you only do it once – for a garden that’ll last 20 or 30 years.

Keeping PVC Pipe Off the Ground

Q.  We don’t understand whether we are to place these 2″ x 3″ (6″ lengths) directly on the soil or are we to nail them to the top sides of the 2″ x 12″s.  If they are to rest directly on the soil surface, how far apart should they be spaced? We are using two PVC watering lines per box.

A.  We recommend 6″-long pieces of 2″ X 4″‘s. They are placed on the soil surface (usually pressed into the soil slightly), and having two small nails in the top to hold the PVC in place. They should be spaced no more than 8’ apart.

Jim Kennard

Correct Hole Placement and Need for Threaded Parts to the System

Q.  I was reading the instructions for automated watering and it says to mark a line and then mark another 30 degrees from that one.  Is it 30 degrees between each line or 45 degrees between each line?  (there are 3 rows of holes in each pipe, right?)

Next, is there any particular reason that the end cap needs to be threaded?  Do you need to take it off for some reason?

How deep are the trenches?  I am guessing that those pipes that go down vertically into the trenches are 1 foot long.  Can they be left in the trenches over winter, without freezing? And, does there need to be a threaded end cap  to allow the water remaining in the pipes down in the trenches, for them to drain–so they won’t freeze over the winter?

PS  I have already purchased all the parts for the system, and I do not have ANYthing with threads on it. 

A.  I apologize that we have two different angles listed for the holes in the PVC pipes.  The 30 degree angle is necessary for narrow beds, such as a 12″ Box.  However, the 45 degree angle is generally more satisfactory, although it shouldn’t make a lot of difference in soil-beds, since the entire planting area is flooded anyway.  In Grow-Boxes, the narrower angle could mean the water isn’t getting very close to the plant roots when the plant is small, and could cause some stress from lack of water, if you don’t make sure of your coverage.

Go back to the store and trade for male threaded ends, female end caps, and threaded ball valves.   Do not make the mistake of building your watering system without having both ends screw off, and the riser from the main line also screwing in (this one is ESPECIALLY important).  And you need to be sure your valve also screws in on both ends.
The end cap needs to come off, so that accumulations of stuff in the pipe can be flushed out.  Otherwise, you will begin to have the pipe fill with sediment, or last winter’s critters-seeking-shelter, and watering will suffer greatly.  Also, if it doesn’t screw, the valve up on top can’t be moved out of the way of the tiller or shovel when someone is re-working the bed.
If the riser from the main line is glued and someone breaks it, you could easily be faced with an expensive and time-consuming repair job.
The valve that controls your water gets a lot of use and abuse, and sometimes there isa break – either in the valved itself or the pipes on either side.  Being able to unscrew it is essential to avoid costly and time consuming repairs.
In designing and building your watering system you need to have a stop and waste valve at the low end of the system, so excess water can drain off.  So long as this is done, and your pipes empty themselves before a hard frost, you will have no problem leaving your individual bed risers in the ground over the winter.
The trenches for your main line should be more than 8″, since that is the depth of the tillers you will use, and you surely don’t want to be cutting into your main water line.

Build an Inexpensive and Highly Effective Automated Watering System

Q.  I am in the proccess of putting in the automated watering system. I have some questions.  When the pipe is intalled down the center of the rows are they permanently installed?  Next year in preparing the garden how do you roto-till the garden with the pipes there. The garden book states to use threaded T’s and elbows.  I can’t figure out why, unless you also buy threaded PVC pipe. I’m confused, please reply as soon as you can.
A.  First you buy unthreaded lengths of pipe (10′ or 20′).  then you glue the lengths together to fit the length of your soil-bed, using slip-slip fittings.  Next you drill 3 holes with a #57 drill bit at 45 degree angles every 4″ the entire length of the pipe (it goes fast, don’t feel intimidated).  The three holes make a 90 degree angle in the pipe, and they face down onto the bed.
Then you put threaded male adapters on both ends of the pipe.  On the far end you will screw a female threaded cap.  On the end with your water valve you screw the male end into the female end of the threaded ball valve.
That ball valve is threaded into a 1 1/2″ bib, which is threaded into a threaded elbow, which is glued to a 1′ piece of 3/4″ pipe that has another male threaded fitting on the opposite end.  That end is threaded into a threaded T that is glued into your main water-source line.  You can sketch all that out and you’ll see the whole system.
OR – do you have the book The Mittleider Gardening Course?  If not I highly recommend it.  OR – go to the Store section of the website and look at that book.  We have made that very chapter available for you to read, study, and download – free of charge.
You place the pipe on short pieces of 2″ X 4″ boards 5 or 6″ long – 4 or 5 to a 30′ bed.
At the end of the season you just remove the pvc pipe and turn the short PVC piece with the ball valve toward one of the stakes, and the bed is ready to till.  I like to till in the fall, so there is less opportunity for weeds to winter over and get ahead of you in the spring.

True Cost of Installing an Automated Watering System?

Q.  I’m planning to install the automated watering system for my 18 raised Grow-Boxes.  I thought it was supposed to be inexpensive, but I’m nearing $300 for the PVC and fittings so far.  Maybe I’m buying the wrong things.  Can you give me the detailed list of what I need, and an estimate of what my 18 bed watering system should cost?

A.  In Salt Lake City, Utah  I would pay approximately the following for 18 beds, including risers from a main line.  I have not included the cost of your main line to the garden, since I don’t have any facts.

18 – 3/4″ T with Riser side threaded – – – – – – – – – – –  $ 13
54 – Male threaded adapters –  glue to pipe ends – – –  25
18 – Sch 200 pipe for risers 1′ each – – – – – – – – – – – –      2
18 – Slip/thread elbows – – – – – – – – – – – – – – – – – – – –      6
18 – 1 1/2″ nipples  – – – – – – – – – – – – – – – – – – – – – – –     6
18 – Plastic threaded ball valve – – – – – – – – – – – – –       72
54 – 10′-long 3/4″ Sch 200 PVC pipe – – – – – – – – – – –    60
36 – slip/slip connectors to make 30′ lengths – – – – –       9
18 – threaded end caps – – – – – – – – – – – – – – – – – – – – –   9

Total – approximately $202. 

This represents a 20 year investment of  $10 per year, which is less than 6 cents per day of a 6 month growing season.  It will will save you money every day for 20 years on water, plus the time required for watering, and it will make the water distribution more accurate and effective.  We consider it a very inexpensive investment, with a high rate of return.

How High are the Pipes From the Soil Surface?

Q.  I have a question concerning the height of the pipes in grow boxes.  The book says to lay 2″ X 4″ X 6″ blocks down across the bed width, but shows two pictures – one with the block laying flat, which would put the pipe 1.5 inches off the ground. The othe picture shows the block on its side, which would put the pipe 3.5 inches off the ground. What is the recommended height or what works best?

A.  The PVC pipes must provide water to the roots of your plants.  In order to do this the height of the pipes from the ground may need to be different, depending on circumstances.  In an 18″-wide Grow-Box, we recommend the pipes be at least 3 1/2″ from the soil surface.  The reason is that the water will not travel very far horizontally, but goes mostly DOWN when it hits the soil.  Therefore, it is important to get the water spray close to, but not hitting the plant stems.  Otherwise you will waste water, and your plants may not get enough.  On the other hand, if the water hits the plant stems – particularly when they are tiny, it may wash them right out of the soil and kill the plant. 

If plant stems are 2″ from the sides of an 18″ box, pipe sitting 3 1/2″ from the soil surface on a 2″ X 4″ block will be 6″ MOL from the plant stems.  With holes drilled at 45 degree angles, the water will hit the soil 2 to 2 1/2″ from the stems.  Once the plant is established, or if you’re using transplants, the root systems will go deep enough that the water will reach them.  But with plants from seed, the water may not be close enough during the first 2-3 weeks.  If this is the case, you may need to raise your pipes another inch or so. 
In Soil-Beds, unless you are growing in very sandy soil, the water will generally fill the entire bed from side to side and end to end, and so the height of the pipes from the dirt is not as important, so long as you do not wash your plants out of the ground by having the water hit the plant stems.  It is still most efficient to place the water close to the plant stems, and so a 2″ X 4″ block works well.
Some pictures you see from the Mittleider books may be of 12″-wide Grow-Boxes, in which case the pipes would not need to be as high off the soil surface in order to have the water reach the plants’ root systems.

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.