Greenhouse Watering Setup: Build Before the Benches Fill

Use the accessible period, whatever the month

The easiest time to build greenhouse watering is before benches, grow bags and dense foliage obstruct the route. February can provide that opportunity in some UK gardens, but climate, greenhouse use and crop plan differ. The real trigger is an accessible structure and enough frost-free time to commission the water path safely.

This page covers source, routing, filtration, delivery layout and commissioning. Schedule calibration belongs in the greenhouse schedule guide, and holiday resilience belongs elsewhere.

Draw the structure before buying pipe

Measure:

• greenhouse length and width;
• bench and bed positions;
• safe entry point for supply pipe;
• door, vent and moving-frame clearances;
• distance and height change from the water source;
• filter and regulator access;
• flush-end locations;
• plant groups expected during the season.

Sketch the path and photograph every proposed penetration. Never drill greenhouse glass. Use an existing service opening or a suitable non-glass panel only when the structure's instructions and competent practice allow it.

Choose the water source

Mains outside tap

A suitable mains tap can feed a timed greenhouse circuit through correctly rated components. Measure flow and confirm pressure against the timer, regulator and delivery-hardware limits.

Gravity-fed water butt

Height alone may not provide enough pressure for a valve or pressure-compensating emitter. Do not buy on the assumption that a timer “works with rainwater”. Check the published minimum pressure and test the actual head and flow.

Pumped stored water

A pump can provide pressure but adds electrical safety, filtration, dry-run, non-return and control requirements. Use equipment designed for the source and follow its manual. Do not locate unsuitable electrical equipment in wet greenhouse conditions.

Whichever source is chosen, current restriction notices and supplier rules still apply.

Measure the available flow

At the intended connection point, collect a known volume and time it:

litres per minute = collected litres / seconds x 60

Repeat under representative conditions. This result is a source measurement, not a guaranteed emitter output. Pipe length, height, fittings, filter, regulator and emitters all affect final delivery.

Compare total proposed circuit demand with current component specifications and keep a practical margin.

Route the supply safely

A supply line should not be crushed by the door, heated against glazing, create a trip or pull on the timer. Use a sleeved, protected route through an appropriate panel or a guarded low-level door route only when it can remain clear.

Anchor the line just inside the greenhouse so movement outside does not drag emitters from pots. Support bends without kinking pipe. Leave a service loop where a filter or regulator needs removal.

Keep line clear of heaters, sharp staging edges and cultivation tools.

Fit regulation and filtration

Fine emitters and drip line often require filtration; delivery hardware may require pressure regulation. Confirm order, orientation and limits in the component instructions.

Keep the filter visible and removable. A filter hidden behind a full bench will not be maintained. Provide an accessible flush point at the end of each circuit.

Do not assume the timer itself regulates pressure or filters debris unless its current specification explicitly says so.

Choose root-level delivery

Point emitters

Useful for individual pots and grow bags when tubes can be secured and output checked. They need maintenance as containers move.

Inline drip line

Useful for compatible rows or border crops after a wetting-pattern test. Line position should follow roots, not simply the greenhouse edge.

Capillary systems

Can suit compatible pots on a level bench when operated and cleaned according to their design. They are not interchangeable with point-emitter output assumptions.

Propagation mist

Misting is a separate humidity and propagation process. It may require nozzle pressure, filtration and short repeat intervals that an ordinary tap timer cannot supply. Keep it separate from established-crop root watering.

Build one section first

Install the source connection, required regulator and filter, then one short representative delivery section. Flush new pipe before closing ends or fitting fine emitters.

Run the section and check:

• every joint for leaks;
• near and far output;
• emitter security;
• drain and flush access;
• root-area wetting;
• complete valve closure.

Correct the design before extending it across the greenhouse.

Commission an empty system carefully

An empty bench cannot prove a future plant schedule, but it can prove hydraulic and operational facts. Use catch containers to compare outputs. Observe a scheduled start and stop. Exercise local control and the physical supply shut-off.

Photograph pipe routes before pots conceal them. Label circuits by future plant job. Record filter, regulator, emitter type, measured output and component versions.

When plants arrive, begin the seven-day horticultural calibration; do not convert the empty-system test runtime into a crop recommendation.

Protect ventilation and hygiene

Watering hardware must not obstruct roof vents, louvres, doors or shading. Keep the floor free of persistent water and route flush discharge safely.

Clean reusable parts according to their instructions. Do not allow stagnant water in open catch containers or disconnected tubes. Inspect for algae and blocked emitters through the season.

Where Johgee fits

A greenhouse can be one independently scheduled group within a larger garden. Johgee's current four-zone RF specification may fit when the water source, pressure, flow and radio path are verified.

The timer remains at the tap; it does not make a poor greenhouse route safe or remove the need for filtration, regulation and physical output checks.

Pre-season acceptance record

Keep:

• layout drawing and photographs;
• source flow and pressure evidence;
• component manuals and versions;
• filter and regulator details;
• near/far output comparison;
• watched automatic closure result;
• flush and winter-removal points;
• date plants were added and calibration began.

Field evidence from our garden

Sources

• RHS greenhouse ventilation and shading
• RHS container watering
• GARDENA installation and flushing guidance
• Johgee four-zone RF timer specification

How this guide was prepared

The former page claimed February was universally the greenhouse year's beginning and treated pressure as certain. This revision makes access, source measurement and component instructions the gates. It separates empty-system commissioning from plant scheduling and avoids universal sowing dates, pressure assumptions, runtimes or installation-time promises.

Checked 16 August 2026.