Sprinkler pipe and fittings: PVC vs poly, Schedule 40 vs Class 200, and what size you need
Which pipe to use for a home sprinkler system in the US: PVC Schedule 40 or Class 200 for mains and laterals, poly pipe in cold climates, swing joints at the heads. With a friction loss chart in PSI per 100 ft, the 5 ft/s velocity rule, and the fittings that do not leak.
Two kinds of pipe in every system
A sprinkler system has two very different pipes. The mainline runs from the point of connection, through the backflow preventer, to the zone valves, and stays under full house pressure 24 hours a day. The laterals run from each valve to its heads and are only pressurized while that zone runs. They do not need the same pipe, and treating them the same is where a lot of DIY systems overspend on one side and cut corners on the other.
This guide covers which pipe, which size and which fittings. Where to route it and how deep: /enHow to bury irrigation pipes: depth and techniques.
PVC, poly, and where each one fits
Rigid PVC is the standard across most of the US: cheap, easy to glue, smooth inside. Schedule 40 has thick walls and is the usual choice for the always-pressurized mainline. Class 200 (SDR 21) has thinner walls, a larger inside diameter and lower cost, and is common for laterals. Some jurisdictions specify the mainline material, so check before you buy.
Polyethylene (poly) pipe is the alternative in cold climates: it is flexible, follows the trench in long coils, tolerates some ground movement and is the pipe you can pull with a vibratory plow. It loses a little more pressure than PVC of the same nominal size and is joined with barbed insert fittings and stainless clamps. Between lateral and head, both systems use a flexible swing joint or funny pipe, so the head can be set to grade and a mower hit does not crack the pipe.
Friction loss chart: PSI lost per 100 ft
Every foot of pipe costs pressure, and the cost rises steeply with flow. The chart shows the loss per 100 ft at common zone flows, with water velocity in parentheses. Values above about 5 ft/s are where the industry rule says to go up a size, both for pressure and because fast water causes water hammer when valves close.
| Pipe | 5 GPM | 8 GPM | 10 GPM | 15 GPM |
|---|---|---|---|---|
| PVC Sch 40, 3/4 in | 2.2 PSI (3.0 ft/s) | 5.1 PSI (4.8 ft/s) | 7.8 PSI (6.0 ft/s) | 16.5 PSI (9.0 ft/s) |
| PVC Sch 40, 1 in | 0.7 PSI (1.9 ft/s) | 1.6 PSI (3.0 ft/s) | 2.4 PSI (3.7 ft/s) | 5.1 PSI (5.6 ft/s) |
| PVC Class 200, 3/4 in | 1.2 PSI (2.4 ft/s) | 2.9 PSI (3.8 ft/s) | 4.3 PSI (4.7 ft/s) | 9.1 PSI (7.1 ft/s) |
| PVC Class 200, 1 in | 0.4 PSI (1.4 ft/s) | 0.9 PSI (2.3 ft/s) | 1.3 PSI (2.9 ft/s) | 2.8 PSI (4.3 ft/s) |
| Poly (IPS), 3/4 in | 2.4 PSI (3.0 ft/s) | 5.8 PSI (4.8 ft/s) | 8.8 PSI (6.0 ft/s) | 18.7 PSI (9.0 ft/s) |
| Poly (IPS), 1 in | 0.8 PSI (1.9 ft/s) | 1.8 PSI (3.0 ft/s) | 2.7 PSI (3.7 ft/s) | 5.8 PSI (5.6 ft/s) |
What the chart means for sizing
A rotor zone at 10 GPM through 100 ft of 3/4 in Schedule 40 loses almost 8 PSI, and the water moves at 6 ft/s; the same run in 1 in Schedule 40 loses 2.4 PSI. On a 50 PSI house that difference decides whether the last head reaches its rated radius. The price difference between the two sizes for a typical lateral is a few dollars.
A practical rule for homes: 1 in for the mainline and for any lateral that carries a whole zone over a long run, 3/4 in for short laterals and branch runs under about 8 GPM, and 1/2 in only for the swing joint to each head or for drip. Add the loss through the backflow preventer, the valve and fittings, plus 0.43 PSI for every foot a head sits above the source, and you have the pressure the head really gets. That is the number to read the nozzle chart with: /enIrrigation Design Mistakes: A Pre-Installation Checklist to Avoid Dry Spots and Soggy Zones.
Fittings that do not leak
- PVC solvent weld: cut square, deburr, dry-fit, then primer and cement on both pipe and fitting, push home with a quarter turn and hold for a few seconds. Most leaks in glued systems are skipped primer or pipe not fully seated. Let joints cure before pressurizing, per the cement label.
- Threaded joints: PTFE tape or thread sealant rated for plastic, wrapped with the thread direction. Do not overtighten plastic female threads; they split.
- Poly insert fittings: barbed fittings pushed fully in, secured with stainless steel clamps; warm the pipe end in hot water in cold weather to make insertion easier.
- Saddle tees and compression couplings: fast for repairs and for adding a branch to an existing line without cutting it apart.
- Swing joints at every head: a flexible connection between the lateral and the sprinkler absorbs settling and mower impact and makes it easy to set the head at grade.
The point of connection and the backflow preventer
Everything up to and including the backflow preventer is potable plumbing and falls under your local plumbing code: material, size, the device type (pressure vacuum breaker or reduced-pressure assembly), height above the highest head for a PVB, and often a permit and a licensed installer. Many cities also require an annual test of the device. Plan the mainline size from the tap through the backflow preventer to the valves on the flow of your largest zone, and include the loss through the device itself, which the manufacturer publishes.
Counting pipe for your parts list
Measure the trench routes on a scaled plan, add about 10% for bends and waste, and count fittings at every tee, elbow and head. In SprinklerMap the parts list comes straight from the drawing: pipe lengths by run, fittings and heads, so you buy once. Common mistakes to avoid: 1/2 in pipe for whole laterals, mixing Class 200 into a mainline the code wants in Schedule 40, skipping primer, and burying anything before a pressure test with the trench still open.
Frequently asked questions
What size pipe for a sprinkler system?
Size by flow, not by habit. Keep water velocity at or below about 5 ft/s: that means roughly up to 8 GPM in 3/4 in Schedule 40 PVC, up to about 13 GPM in 1 in Schedule 40, and somewhat more in thinner-walled Class 200. Long runs need the next size up to keep friction loss reasonable.
Schedule 40 or Class 200 PVC for sprinklers?
Schedule 40 has thicker walls and is the usual choice for the pressurized mainline before the valves. Class 200 is thinner-walled, cheaper, has a larger inside diameter and loses less pressure; it is common for laterals after the valves. Check what your local code requires for the mainline.
PVC or poly pipe?
PVC is standard across most of the US. Polyethylene (poly) pipe is common in cold northern climates because it is flexible and tolerates some freezing better, and it is easier to pull in with a vibratory plow. Poly loses a bit more pressure than PVC of the same nominal size and uses insert fittings with clamps instead of glue.
Recommended products
These product links are affiliate links: if you buy on Amazon or AliExpress through them it costs you nothing extra, but it helps us keep SprinklerMap alive as a project and create new useful content.
| Product | Description | Price (€) | Buy |
|---|---|---|---|
| Poly irrigation pipe 3/4 in, 100 ft coil | IPS polyethylene pipe for laterals, common in cold climates because it is flexible and follows the trench. Joined with barbed insert fittings and stainless steel clamps; check the pressure rating before using it for an always-pressurized mainline. | ~€30-60 | Amazon |
| PVC primer and cement set | Primer and solvent cement for Schedule 40 and Class 200 PVC. Primer on both pipe and fitting, then cement, push home with a quarter turn: skipped primer is the most common cause of leaking glued joints. | ~€10-20 | Amazon |
| Sprinkler swing joint / funny pipe kit | Flexible connection between the lateral and each head, with barbed elbows. Lets you set heads exactly at grade and absorbs mower and settling stress so the pipe does not crack. | ~€15-35 | Amazon |
| PVC saddle tee for adding a branch | Clamps onto an existing PVC line to add an outlet without cutting the pipe apart; useful for repairs and for adding a head or drip branch. Match the saddle to your pipe size and outlet thread. | ~€5-12 | Amazon |
| Product | Description | Price (€) | Buy |
|---|---|---|---|
| PE pipe 20 mm 50 m roll (AliExpress) | Polyethylene pipe 20 mm for secondary lines. Flexible, UV-resistant. 50 m roll at highly competitive price compared to local suppliers. | ~€12-28 | AliExpress |
| Assorted 25 mm compression fitting kit (AliExpress) | Set of PE compression fittings: T, elbows, couplings, caps for 25 mm pipe. Tool-free connection, rated to 6 bar. Generous quantity at low cost. | ~€8-22 | AliExpress |
Technical note: Friction loss is calculated with Hazen-Williams (C = 150 for PVC, 140 for poly) using nominal inside diameters: Schedule 40 3/4 in 0.824 in, 1 in 1.049 in; Class 200 3/4 in 0.930 in, 1 in 1.189 in; IPS poly as Schedule 40. Fittings, valves and backflow devices add their own losses. Local plumbing codes govern the potable-water side up to and including the backflow preventer.