“1/2 inch” drip tubing isn’t 1/2 inch across. Most brands make it in three real sizes: .620", .700" and .710" across the outside.
What’s printed on the tubing?
Look along the tubing for a number like .700 OD. Most makers repeat it every few feet.
How wide is it next to a dime?
Hold a dime against the cut end of the tubing.
You most likely have
.620" drip tubing
Sold as 1/2", .520" inside. DIG’s compression fittings for it have a green insert.
On the package: .620 OD x .520 ID
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.700" drip tubing
Sold as 1/2", .600" inside. DIG’s compression fittings for it have a black insert. Rain Bird calls it 700 series.
On the package: .700 OD
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.710" drip tubing
Sold as 1/2", .620" inside. DIG’s compression fittings for it have a blue insert. Rain Bird calls it 710 series.
On the package: .710 OD
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16–17 mm dripline
Rain Bird XF (0.634") and Netafim Techline CV (0.660") take their makers’ own fittings, not .700" or .710" compression.
On the package: 16 mm or 17 mm dripline
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.620" tubing or 16–17 mm dripline
All are narrower than a dime. A caliper tells them apart: .620", 0.634" (Rain Bird XF) or 0.660" (Netafim).
On the package: .620 OD, or 16 mm or 17 mm dripline
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.700" or .710" tubing
They’re only .010" apart, too close for a coin or a tape. Check the print, or use a universal fitting, which fits all three half-inch sizes.
On the package: .700 or .710 OD
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A compression fitting is made for one of the three sizes, so read the size printed on the tubing before you buy fittings.
Find your size
Most makers print the outside diameter (OD) and inside diameter (ID) on the tubing every 5 feet or so. Look for a number like .700 OD. If there’s no print, measure across the outside, or use Identify it. The three main sizes are only .010" to .090" apart, so a caliper is far easier than a tape.
The insert colors are the ones DIG uses on its compression fittings; check the size printed on any fitting package, since not every brand uses the same colors. The full chart below adds the Rain Bird and Netafim sizes.
Which fitting to use
- Compression fittings push over the outside of the tube, so they must match the OD exactly. Know the outside diameter before you choose a compression fitting size.
- Barbed fittings push into the inside of the tube, so they follow the ID. Because IDs vary, use them only at 15 psi or less.
- Universal (nut-lock or spin-lock) fittings clamp a range of sizes. They fit all three sizes of half-inch tubing. That makes them the safe choice when you’re mixing brands or can’t read the size.
- Rain Bird Easy Fit fittings take 0.630" to 0.669" OD (16–17 mm dripline), not the .700" and .710" tubing.
Joining two brands: measure both tubes. Two .700" tubes join with any .700 compression coupling; a .700" and a .710" tube need a universal fitting.
1/4 inch tubing varies too
Rain Bird XQ and DIG poly micro tubing are .170" ID by .250" OD. DIG also sells 1/4" vinyl tubing in .156" x .245" and .160" x .220".
Connecting drip tubing to a faucet
Drip systems run at low pressure, so a faucet hookup needs more than an adapter. Put the parts in this order, starting at the faucet:
- Backflow preventer (3/4" female hose thread in, male hose thread out). It keeps garden water out of the house supply.
- Filter, so grit doesn’t clog the emitters.
- Pressure regulator. DIG’s and Rain Bird’s faucet regulators are preset to 25 psi. Install it after the filter.
- Swivel or hose-thread adapter sized to your tubing’s OD.
Rain Bird sells the first three as one faucet connection kit. Don’t use thread tape on these hose-thread parts; the washers seal them.