Winterise Irrigation System: How to Protect Your Garden

Before the frosts arrive, you must winterise irrigation system networks to prevent catastrophic pipe bursts.

Investing in an automatic garden watering system is a fantastic way to keep your lawn and borders lush, but the British winter can deal a harsh blow to unprotected pipework. When trapped water freezes, it expands with enough force to split MDPE pipes, shatter plastic fittings, and crack expensive solenoid valve bodies.

Finding out your system has been damaged usually happens in spring, when you turn the water back on and notice a drop in pressure or a flooded flowerbed. By then, the repair bill can easily dwarf the cost of a bit of preventative maintenance.

Follow this straightforward guide to winterise your system before the hard frosts set in.

When should you winterise your system?

Ideally, you should look to shut down and drain your system in late autumn (late October to mid-November). Don’t wait until January. Ground-level frosts in the UK often strike overnight without warning, and that’s all it takes to ruin your pop-up sprinklers.

Step 1: Isolate the main water supply

The absolute first step is to cut off the water supply feeding your garden network.

• Locate and completely close the main isolation valve (usually a stopcock near your outside tap or inside the meter pit).
• Head over to your controller (whether you use a Hunter or Rain Bird timer) and switch it to “Rain Delay” or “System Off”. Keep it powered on rather than unplugging it entirely; this keeps the internal backup battery alive and saves your programmed watering schedules for next spring.

Step 2: Clear out the remaining water

Simply shutting the valve isn’t enough—water sitting inside the lines will still freeze and cause havoc. There are two primary ways to clear it out:

1. Manual or automatic drain valves (Gravity method)

If your system was designed with the UK climate in mind, you should have drain valves installed at the lowest points of your pipework. Once the main supply is isolated, open these valves manually (or let the automatic ones do their job) to let the water drain away into the subsoil.

2. The compressor blowout (The professional choice)

This is the most reliable method because it forces 100% of the moisture out of the intricate internal parts of your sprinklers and valves.

• Connect a suitable air compressor to the blowout port located just downstream of your main isolation valve.
• Top tip: Keep the air pressure regulated below 3.5 to 4 bar (approx. 50-60 PSI). Excessively high pressure can easily friction-weld or shatter the delicate internals of your pop-up gear drives.
• Cycle through each zone one by one on your controller, letting the air purge the line until the sprinklers are spitting out nothing but a fine mist.

Step 3: Protect your valve boxes and filters

Subterranean valve boxes are notorious for trapping cold, damp air right around your manifold.

• Open up your system filters, pull out the mesh or disc filter elements, give them a thorough rinse, and put them back. Leaving trapped debris over winter can cause the filter casings to crack under freezing stress.
• If your valve box is prone to sitting in standing water, bale it out. You can also pack the empty space inside the box with an insulation jacket or some bubble wrap to shield the solenoids from frosty air.

Step 4: Stash your above-ground kit indoors

Anything exposed directly to the biting winter wind is at the highest risk of frost damage:

• Unscrew any digital tap timers / tap-mounted controllers from your outside bib taps. Take the batteries out to prevent corrosion, and store the unit somewhere dry and frost-free, like a shelf in the garage or a garden shed.
• Disconnect all garden hoses from your taps. Left connected, trapped water will back up into the tap body, leading to a split brass casting.

Sorted for winter, ready for spring

If you spot any weeping seals, cracked fittings, or faulty valves while carrying out your autumn checks, don’t leave them to worsen over the winter months.

At MB Irrigation, we keep a massive, permanent stock of original spare parts, MDPE compression fittings, and commercial-grade pipework ready for immediate dispatch across the UK.

Based in the Warrington area? Our trade counter team is always on hand for local collections and technical advice. Drop us a line at contact@mbirrigation.co.uk and we’ll help you get your system sorted.