What do I actually need to do in order to size/buy a DIY drip garden watering system?

Question

I'm looking at adding a drip-watering system to my garden. I have a garden that is about 500 square feet, with roughly 40 tomato/pepper sized plants, a handful of raspberries, and about 100 feet worth of peas/green beans.

I'm trying to figure out what I need to order from Amazon for a drip system, but it's surprisingly difficult (I can't find any drip system components in local stores to 'build my own').

I'm guesstimating that I'll need:

• 100 feet of 1/2 tubing
• 250 feet of 1/4 tubing
• 40 drippers for the plants (1 gallon/hour?)
• Some 1/4 tubing with holes for the peas/green beans
• A bunch of 1/4" connectors
• regulator
• timer
• standard hose adapter
• ??

Is there a good way to design this other than trial/error? I can't find anything online short of overbuying a kit.

Answer 1

You can assemble a drip irrigation system on your own. If you’re the least bit handy, it’s not difficult at all. The system operates at low pressure, so the seals are as simple as punching a hole in a plastic tube and shoving in barbed fittings. For the larger fittings, a warm day and/or a rag with hot water to prewarm the inserted end do help.

It’s fairly straightforward to assemble what you imagine will work. Try it. If a plant looks too dry, give it another emitter. It’s really flexible, and fun if you like that kind of thing. For me it works beautifully for ornamentals. Here are some guidelines for buying parts for a vegetable garden.

Research each crop you grow to see how much water it needs in the driest part of summer. Figure it out in gallons per week either per plant or per foot of row. For large plants like squash or tomatoes, split the total among 3 or 4 emitters, to reach the roots that extend out from the stalk. Dry spots may still be a problem - see the second half of this reply. You may water twice a week, or maybe more often - depends a lot on your soil and climate. Put that into the math. You should end up with a table of emitter sizes. This all takes some time but either you wing the whole thing or do this work up front. Maybe there’s a website that has it all, though I’m afraid I can’t help you there.

• For each emitter get one straight connect (to attach the ¼” hose to the ½” main line). That might be a little bit more than you need but not much.

• Get a fistful of ¼” T’s, maybe a quarter as many as straight connects. They are handy for splitting a ¼” tube instead of attaching each separately to the main line.

• Buy the minimum order of goof plugs. They fix a ½” main when you make a hole that later you decide you don’t want, or even want to abandon a ¼” line in place, perhaps temporarily. Buy a hole punch.

• Figure out how you want to connect to your water source, and get the pieces for that. It’s hard to give generic suggestions about this part. It might be as simple as one connection between ½” drip and a hose, with a built-in screen. It could involve a pressure reducer, filter (protects your system - don’t skimp), etc. As a comment noted, if it’s a continuous connection such as with a timer, the backflow prevention part is important! If you are going to use multiple stations, get a more flexible controller than you think you will need. The components inside a valve box get complicated and I won’t make this reply even longer by describing them.

• Draw your ½” hose layout, in a way that puts main line within a couple feet of each emitter. Calculate the total length plus 10-25% for surprises and waste. Where the line goes around corners, list a ½” corner. Note each T intersection. You might even need a 4-way junction. If you can make the whole ½” hose layout into a loop the pressure will be more even. For each ½” dead end, buy an end fitting. The figure 8’s work pretty well and are less expensive, but the kind that unscrew are nice when you flush out the system each spring - an important task. While you’re figuring out the ½” pieces, throw in a couple straight connects. They are handy if, no, when, you put a shovel through a line that hid under a plant, you need to rearrange the layout, etc.

• It’s hard to say how much ¼” hose you’ll need but compared to the rest of the pieces it’s cheap. Get at least as much as you need of 1/2” main.

BUT, big caveat: Typical drip irrigation isn’t a panacea for vegetable gardens.

1. Following good gardening practices, you’ll plant different crops in different parts of your garden each year. Then the emitter layout that worked for this year’s tomato plants in the far corner and peas next to the fence gets reversed and it’s a mess. It can be reconfigured, but with a lot of wasted effort and some wasted supplies. This is the main reason I don’t use regular drip irrigation for vegetables.

2. Drip emitters don’t work well for row crops. Water needs to be delivered at relatively short intervals - every 4-10” depending on soil type. (No matter what system you use, some hand watering of seeds and tiny seedlings remains necessary.) Quarter inch soaker hose can work. But the classic kind puts out quite a lot of water compared to emitters. (We’ll get to microperforated in a minute.). So in order to get enough water to the tomatoes with emitters, you’ll have to put a lot of water on the row crops. In large gardens, there’s an additional problem with ¼” soaker hose. Plants near the ½” main water get ample water. The water can’t flow sufficiently smoothly = quickly through the tiny inner tube to reach plants farther away. There are many opinions about an exact maximum run. It’s under 100’ - in my experience, a lot less.

3. In the spring it’s usually a waste to water unplanted areas. When it’s time to cure potatoes it’s best to turn off the water. Etc. You may be able to build zones into your ½” hose layout with little twist valves. May. If you can, do.

4. The connection between the water source and main line is a problem. If hard PVC is involved and it freezes where you live, the system has to be blown out with a compressor every fall. If not, it’s virtually impossible to set up a water-tight connection to a metal pipe fitting. One alternative is to turn the water off and on manually each time you need to water, but that defeats the idea of a timer. The other alternative is connection with a flexible pipe. In that case the pressure needed for even drip irrigation will cause endless weeping - the hose kind, mostly.

5. In landscapes one way emitters save water is to leave dry areas that can be. But in a vegetable garden, you probably want nearly all soil to be watered. Otherwise roots won’t grow there. Even individual plants like tomatoes need a large moistened area all around them.

My preferred alternative is T-tape. I run parallel strips 1' apart down each raised bed no matter what grows there. Simple plastic valves in ½” (drip) main line isolate each bed. T-tape works at even lower pressure than drip. The permanent connection to the water main still leaks a little after years of fiddling, but less than my drip system did. So do some of the connections between the tape and ½” line (my garden is big enough that I also use ¾”, an option some gardeners may want to know about), teaching me to buy good quality connections for that part. The t-tape is connected to a professional-grade controller and a valve box. In the fall I open the filter to let air into the system and that’s all the blowing out it gets or needs. It’s not perfect, but after a lot of looking and experimenting it’s the best solution I’ve found.

There are now multiple vendors of T-tape. In suggesting dripworks.com I’m not saying they are necessarily the best, just the one I’ve used. Their website can help you decide particulars like thickness of tape, emitter spacing, and separation between lines. Any system that lets us use water wisely is good, and drip may work well for you. Just go into it with your eyes open about the trade-offs.

Answer 2

In general, I find ordering from Rainbird's website to be cheaper (and have more options) than ordering from Amazon for almost everything except tubing. Components (elbows, T-splits, emitters, etc...) are much cheaper. On the other hand, tubing (even Rainbird's tubing!) seems to be cheaper on Amazon.

Also check Rainbird's clearance section, I found some fantastic tubing with emitters pre-set 12" apart that were dramatically reduced cost, which worked fantastically on my raspberries (and which I'll also use for rows of plants like corn, melons, etc...). If they still have it on such extreme clearance (Here it is, still on sale), I'd suggest picking up two rolls of that - one for your greenbeans and peas, and one for your raspberries. The GPH of it is 0.62 per built-in nozzle - about a half gallon GPH. They also have the 18" spaced version on sale, but I personally stocked up the 12", since it suited my needs better.

Rainbird charges shipping unless you spend over $100, and not if you order tubing, but even with shipping charges, their prices on components still saved me alot of money.

I'd suggest mapping out your irrigation plan on paper, and how ever much irrigation you think you need, order extra tubing and extra components, and if you don't need them, save them for later expansion.

For 1/2 tubing, I find it cheapest to buy 500' rolls on Amazon for $45, but if you never plan on expanding your irrigation, it might be overkill for your needs.

I use 1 GPH emitters for most things (including tomatoes, strawberries, blackberries), but 2 GPH emitters for trees and perennial bushes (and the 0.62 tubing w/ built-in emitters for my raspberries). The amount doesn't super matter, you could just run your irrigation for longer or shorter periods of time to emit the same amount of water.

For standard hose adapters, get a standard metal hose adapter for 1/2 hoses (but that screw into standard hose pipe threads) - the plastic hose adapters keep getting threaded on me, and one even split in two. I'm moving all my "irrigation to faucet" connectors to brass.

For timers, I really like this 3-port Orbit water timer. They've lasted me two years now, are easy to program, have very convenient "Rain delay" and "Manual run for N minutes" settings. All three ports are programmable to different schedules also. I made the mistake of originally buying just a single port one (also from Orbit), but rapidly had to upgrade to a three-port to put different kinds of plants on a different schedules, and because I need to water so much that I can't run them all at the same time or the pressure drops too low - one of the reasons I needed so much 1/2 tubing - different lines leading to different parts of the garden.

The only downside for that timer is remembering to take it in during the winter. Other than that, it sits out there in the hot sun and rainy days perfectly fine.