Water Timer for Greenhouse Drip Irrigation UK: Plan Two Zones

Divide the greenhouse by moisture need

A useful zone is a group of plants that can share a watering decision. Seedlings in small modules may dry differently from established tomatoes in grow bags; patio containers outside the greenhouse may face more wind. Putting unlike plants on one programme recreates the uneven hand-watering problem that automation was meant to solve.

For the precision grower worried that inconsistent watering will dry seedlings or leave tomato roots saturated, the aim is repeatable delivery and observation. Independent outlets help only after the groups are sensible.

Start with source pressure, not the timer display

The WaterOutle listing publishes a 0.5–8 bar working range. That describes the timer, not the pressure required by every dripper. Mains-fed and gravity-fed systems behave differently, and a normal raised water butt may be below the timer's minimum. If you need stored rainwater, choose a timer and emitters explicitly rated for low pressure or use a correctly specified pump.

For a mains connection, follow current backflow-protection requirements. Hozelock's UK installation guidance directs users to the Water Supply (Water Fittings) rules and WRAS guidance and shows backflow protection in the connection sequence. If an old tap's protection is unknown, ask the water supplier or a qualified plumber rather than assuming it is built in.

Build the line so it can be checked

Follow the exact order and pressure limits in the chosen drip-kit instructions. A typical plan needs the timer, a clean filter, a pressure reducer where the emitter maker specifies one, mainline pipe and correctly placed emitters. The RHS guide to garden watering methods explains that drip lines deliver water slowly at root zones and can be automated, while pressure and coverage still need adjustment.

• Filter: prevents grit reaching small emitter passages; inspect it as part of routine maintenance.
• Pressure control: matches the supply to the chosen line rather than relying on the timer's maximum rating.
• Mainline and branches: keep runs understandable so a weak final dripper can be traced.
• Emitter placement: target the active root zone and keep water away from paths and electrical equipment.

Commission each outlet with a catch-cup test

1. Flush new pipework as directed before fitting small emitters, then clean the inlet filter.
2. Use manual mode to run outlet one. Put identical containers under representative near and far emitters for the same measured interval.
3. Compare the collected volumes. Investigate a large difference for kinks, blockage, pressure loss or mismatched emitters.
4. Repeat on outlet two, then test the intended staggered programmes with the tap fully in its operating position.
5. Check the growing medium at root depth after the cycle and again before the next planned cycle. Adjust from that evidence.

This test answers the low-pressure objection more honestly than watching water leave the first dripper. A line can look active near the tap while seedlings at the far end receive too little.

Set a schedule from plants and weather

The RHS recommends early-morning watering because evaporation is lower and plants can use the moisture through the day. It also warns against a rigid “once a week” routine: weather, soil or compost, establishment and plant size change demand. Evening can work, but damp foliage overnight may encourage disease, so drip to the root zone and inspect the greenhouse.

Start with a conservative duration, then change it from root-zone moisture and catch-cup results. A rain delay can pause the outdoor zone after meaningful rain, but rain may not reach covered greenhouse pots. Two zones let you pause one without assuming the other received water.

Check restrictions before using mains water

A UK hosepipe ban is formally a Temporary Use Ban. Section 76 of the Water Industry Act allows a water undertaker to prohibit specified uses including watering a garden by hosepipe and requires notice of the ban's terms. Some supplier notices define narrow conditions for drip or trickle systems; others may word restrictions differently. Always read the live notice for the supplying company.

Failure checks before leaving it unattended

• A blocked emitter can leave one plant dry while the rest of the zone looks normal.
• A detached line can empty water onto the floor; secure connections and inspect under pressure.
• Low pressure can starve the end of a run; repeat catch-cup checks after changing the layout.
• A fixed programme can overwater after cooler weather; review root moisture rather than “set and forget”.
• Battery or valve failure can stop a cycle; use the manual's indicator and maintenance routine.

For tap-side fitting and first programming, use the how to set up a hose timer UK guide. If the timer type itself is undecided, the water timer for irrigation guide keeps that buying decision separate.

Frequently asked questions

Can this timer run greenhouse drip irrigation from a water butt?

Only if the water source and complete system meet the timer's published 0.5–8 bar range and the drip kit's requirements. Many gravity-fed water-butts are lower pressure, so use equipment explicitly designed for that source or a suitable pump rather than assuming compatibility.

Does greenhouse drip irrigation need a pressure reducer?

It depends on the emitter system and incoming pressure. Use the regulator specified by the drip-kit manufacturer where required, and measure or obtain the supply pressure instead of guessing. Excess pressure can disturb fittings; too little can starve distant emitters.

How long should a greenhouse drip timer run?

There is no reliable universal duration. Emitter rate, pot size, growing medium, crop stage, temperature and wind all change demand. Start conservatively, check moisture at root depth and compare catch-cup volumes, then change duration rather than copying a fixed online schedule.

Can timed drip irrigation be used during a hosepipe ban?

Do not assume it can. A hosepipe ban is formally a Temporary Use Ban and the exact notice from your current water supplier controls the restrictions and exceptions. Check that notice before switching the system on; a timer alone does not create an exemption.