How many sprinkler heads per zone?

The number of heads per zone is limited by your available water flow rate. Pop-up spray heads use about 12 L/min each, so with a typical UK mains flow of 20 L/min, you can run 1-2 pop-ups per zone. Rotor heads use 15-20 L/min each. Drip lines use much less (2 L/hr per emitter) so more can run per zone. Always measure your actual flow rate at the tap.

What pipe size do I need for garden irrigation?

For most domestic garden irrigation, 25mm MDPE pipe is the standard choice. It handles flow rates up to 30 L/min with acceptable friction loss. For longer runs (over 30m) or higher flow systems, use 32mm. 20mm is adequate for small drip-only systems. Use compression fittings for MDPE connections.

How do I calculate irrigation zones?

Zones = Total flow demand / Available flow rate. If you have 5 pop-up heads (60 L/min total) and 20 L/min available, you need 3 zones. Each zone runs separately, controlled by a timer or controller. Keep zones with similar head types together — don't mix pop-ups and drip on the same zone.

How far apart should sprinkler heads be?

Sprinkler heads should be spaced at 50-70% of their radius for head-to-head coverage. A pop-up with 4m radius should be spaced 5.5-8m apart. This overlap ensures even coverage — without it, you get dry spots between heads. In the UK, wind can reduce effective radius, so use the closer spacing.

Do I need a pump for garden irrigation?

If your mains pressure is above 2 bar and flow rate above 15 L/min, you can run a small irrigation system directly from the mains (via a double-check valve to comply with Water Regulations). For larger systems or low-pressure supplies, a pump drawing from a water tank or rainwater harvester is needed. A booster pump adds around £200-400.

TradeCalculator

Garden Irrigation Calculator — Zones, Heads & Pipe

Calculate sprinkler head count, irrigation zones, pipe diameter and water consumption for a garden irrigation system.

Garden Area

Sprinkler Type

Flow: 12 L/min, Radius: 4m

Available Flow Rate

Measure at your outdoor tap

Pipe Diameter

Pipe Run Length

Total pipe needed (0 = auto estimate)

Runtime Per Zone

Sprinkler Head Price

Pipe Price

How We Calculate This

This calculator determines the number of sprinkler heads, irrigation zones, pipe requirements and water consumption for a garden watering system.

Head count

Heads = Garden Area / Effective Coverage per Head
Where effective coverage accounts for overlap between heads (typically 70% of the theoretical coverage area).

Zone calculation

Zones = Total Flow Demand / Available Flow Rate
Each zone runs independently. Water per session = flow rate x runtime x zones.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.