What do I actually need to buy?
Every buying guide gives you the same glossary — tubing, emitters, fittings, a filter, a pressure regulator — and stops exactly where the useful part begins, which is how many. So here is a complete list with quantities, for a garden of 3 raised beds 8 × 4 ft, 20 ft from the tap and 4 ft apart. Change the beds and the arithmetic below the table changes with them.
| Part | Qty | Each | Cost | Bought |
|---|---|---|---|---|
| Backflow preventer (hose thread) | 1 | $8.00 | $8.00 | once |
| Filter, 150 mesh | 1 | $12.00 | $12.00 | once |
| Pressure regulator, 25 psi | 1 | $10.00 | $10.00 | once |
| Hose-thread to ½ in tubing adapter | 1 | $5.00 | $5.00 | once |
| Hose-bib timer | 1 | $30.00 | $30.00 | once |
| Hole punch | 1 | $6.00 | $6.00 | once |
| Goof plugs (pack) | 1 | $4.00 | $4.00 | once |
| ½ in mainline tubing | 31 ft | $0.35 | $10.85 | per garden |
| Inline drip line, 0.9 GPH at 12 in | 80 ft | $0.45 | $36.00 | per garden |
| Tee, ½ in | 3 | $1.50 | $4.50 | per garden |
| Elbow, ½ in | 3 | $1.20 | $3.60 | per garden |
| Drip-line coupler | 9 | $1.00 | $9.00 | per garden |
| End cap / figure-8 closure | 9 | $0.80 | $7.20 | per garden |
| Hold-down stake | 27 | $0.25 | $6.75 | per garden |
| Total | head-end $75 + parts $78 | $153 | ||
Tubing and drip line carry the standard 10% spare for cuts and mistakes and round up to whole feet — you can't buy 79.2 ft. Prices are typical 2026 US retail and are the softest figures here; quantities are the part worth having. This garden draws 65 GPH, comfortably inside what ½ in poly mainline carries (200 GPH), so it's one zone.
Look at the last column. The backflow preventer, filter, regulator, adapter, timer and punch come to $75, and you buy them once no matter how big the garden gets. On a single-bed system that's 71% of the total — the tubing and fittings that actually water the plants are the cheap part. Add beds and the head-end doesn't move: beds two, three and four cost about $24 each.
Which settles the kit-or-pieces question that every vendor page leaves open. A kit is a sensible way to buy your first bed — it bundles that $75 of head-end at a discount and saves you standing in an aisle guessing at fittings. A second kit is buying a second filter, regulator and timer you already own. After bed one, buy tubing, emitters and fittings loose.
How much tubing? Straight from the bed dimensions
Drip lines run the length of the bed, spaced 12 inches apart, set one spacing in from each edge rather than on it — the edge plants are already inside the nearest line's wetted circle, so a 4 ft bed takes three lines, not four. That single rule gives you everything else:
| Bed | Drip lines | Line needed | Emitters | Draws |
|---|---|---|---|---|
| 2 × 8 ft | 1 | 8 ft | 8 | 7.2 GPH |
| 3 × 6 ft | 2 | 12 ft | 12 | 10.8 GPH |
| 4 × 4 ft | 3 | 12 ft | 12 | 10.8 GPH |
| 4 × 8 ft | 3 | 24 ft | 24 | 21.6 GPH |
| 4 × 12 ft | 3 | 36 ft | 36 | 32.4 GPH |
One bed each, inline drip line with emitters every 12 in at 0.9 GPH. Add 10% when you buy. Mainline is separate: measure tap to first bed, then bed to bed. For point-source emitters on widely spaced plants — tomatoes, shrubs — count emitters per plant instead, which the drip calculator does by plant size.
What it costs as the garden grows
| Beds | Head-end | Tubing & fittings | Total | Per extra bed | Zone |
|---|---|---|---|---|---|
| 1 | $75 | $30 | $105 | — | one |
| 2 | $75 | $54 | $129 | $24 | one |
| 3 | $75 | $78 | $153 | $24 | one |
| 4 | $75 | $102 | $177 | $24 | one |
| 6 | $75 | $149 | $224 | $24 | one |
| 8 | $75 | $197 | $272 | $24 | one |
| 12 | $75 | $292 | $367 | $24 | 2 needed |
8 × 4 ft beds, 4 ft apart, 20 ft from the tap. The head-end column never changes — that's the whole point of it. The zone column is the ½ in line's 200 GPH ceiling; when a garden outgrows it the answer is a second valve, not a longer run time, and the calculator checks it against your tap as well as your tubing.
Laying it out
Mainline along the ends of the beds, not between them. A single ½ in run past the head of every bed, with a tee where each one starts, is shorter, easier to bury under the path and easier to walk without a fork through it than a line that wanders between beds.
Feed each bed from one end. Water enters at the head, runs the length of the bed and stops at the caps. Feeding from the middle looks tidy and halves the pressure available to each direction for no benefit.
Put a shut-off at each tee if the beds do different jobs. Three dollars a valve buys you the ability to stop watering the garlic in June without touching the tomatoes — and it's the poor man's version of the zoning below.
Leave the drip line on top of the soil, under the mulch. Buried line clogs from the outside in and can't be inspected; line lying on bare soil bakes and walks. Under two inches of mulch it stays cool, stays put and stays visible when you go looking.
The build, in order
- Flush the supply. Open the tap with nothing attached and let it run. Grit from the line is the commonest cause of a clogged emitter in week one.
- Build the head-end at the tap. Backflow preventer, then filter, then regulator, then the tubing adapter — in that order, or the filter never protects the regulator. 25–30 psi is what drip wants.
- Run the mainline, unconnected. Lay the ½ in from tap to beds and leave it in the sun for an hour. Warm tubing takes fittings; cold tubing fights you.
- Cut in a tee at each bed. One tee per bed, a short riser up the side, and an elbow over the edge. Add a shut-off at each tee if you want to water beds separately.
- Run the drip lines down the bed. 12 in apart, ending an inch or two short of the far end so the caps aren't buried.
- Stake it before you cap it. Every 3 ft, and at every turn. Unstaked line walks as it heats and cools, and ends up on top of the mulch by August.
- Flush again, then cap. Run water through the open ends until it comes out clean, and only then fit the end caps. This is the step everyone skips and the reason emitters clog.
- Run it and walk it. Watch the last emitter on every line. If it drips like the first, you are done; if it does not, you have found the problem while it is still a fitting.
The two flushes are the difference between a system that works for a decade and one you're unclogging in July. Everything else on the list is recoverable in an afternoon.
Zoning: when one zone isn't enough
Two different things force a second zone, and only one of them is about water pressure.
Hydraulics. A ½ in line carries about 200 GPH and runs about 200 ft before the far end starves, and your tap has its own limit. Past either, you split — and that's arithmetic the drip calculator does from your emitter count and a bucket test.
Plants that want different things. The commoner and more useful reason. Seedlings want little and often; established tomatoes want a lot, rarely. Shrubs want a deep soak once a week; lettuce wants damp all the time. Put them on one valve and one of them is always wrong. Group by watering need first and by geography second — two cheap timers on two taps beat one clever controller on a zone that can't decide what it is.
The mistakes that cost a season
No pressure regulator. House pressure is 40–80 psi and drip wants 25–30. Without one, fittings pop off through the summer and emitters flow far above their rating, so every run time you set is wrong. It is a $10 part and it is not optional.
No filter, or the wrong one. 150 mesh, and clean it twice a season. On well water, make it a habit rather than a plan.
Capping before flushing. Covered above because it's the one that turns a good system into a bad one silently.
Mowing the mainline. Where the line crosses grass, sleeve it in a bit of old hose or bury it properly. Every drip system has one fitting that gets replaced annually and it is always this one.
Never looking at it. A drip system is designed to run quietly under mulch, which means it fails quietly under mulch. Once a month, run the zone and walk it — and once a season, take an end cap off and flush. Ten minutes a year, and the whole thing outlives the beds.
Sources: Colorado State University Extension Fact Sheet 4.702, Drip Irrigation for Home Gardens, and Utah State Extension's home-garden system design guidance (layout, line spacing, head-end order); Rain Bird Landscape Drip Design Guide and supplier flow charts for the ½ in tubing limits used here and on the drip calculator; hold-down and line-spacing intervals as published by drip suppliers. Prices are typical 2026 US retail for individual components, stated as typical — a kit prices differently, which is the point of the fact box.