How to prepare an irrigation system for winter: A step-by-step guide
How to prepare an irrigation system for winter: A step-by-step guide
A burst pipe, damaged sprinkler or leaking filter housing can delay the start of the irrigation season. Often, the cause is water left in the system, which freezes and expands in cold weather. A few well-planned steps in autumn can help reduce the risk of such problems and costly repairs in spring.
How can you protect your irrigation system over winter? In this guide, we explain when to start preparing, how to drain the pipework safely and what to check in sprinklers, filters and driplines. The advice is useful for garden owners, installers, landscaping and grounds maintenance companies, and property managers alike.
Winterising an irrigation system in 6 steps
| 1. Check the system configuration | 2. Flush the lines if required |
| 3. Turn off irrigation and isolate the water supply | 4. Drain or blow out the pipework |
| 5. Protect equipment and fittings | 6. Record the work carried out |
The order may vary depending on the system design and the manufacturer's recommendations.
Why is it important to protect your irrigation system before winter?
Water left in pipes and equipment can freeze and damage PVC pipes, sprinklers, valves, filters or pressure regulators. Polyethylene pipes are more flexible, but that does not mean the entire system is resistant to low temperatures. Above-ground sections and areas where water collects are particularly vulnerable.
The consequences of inadequate winter preparation often only become apparent when the system is restarted in spring. A leak means wasted water, repairs and sometimes digging up part of the site. For installers or maintenance companies looking after several properties, it can also mean additional call-outs and changes to work schedules. An autumn inspection helps identify worn components early, plan replacements and prepare for the next season with fewer concerns.
When should you prepare your irrigation system for winter?
Ideally, winterisation should be completed before the first frost that could damage unprotected parts of the system. If forecasts indicate night-time temperatures approaching 0°C, it is best not to delay. However, the exact timing depends on the climate, the location of the site and how the system is installed.
| Region | Approximate period | What determines the timing? |
|---|---|---|
| Northern Europe | September–November | In colder areas, preparation may be necessary as early as the beginning of autumn. |
| Central Europe | October–November | Pay particular attention to forecasts of overnight frost. |
| Southern Europe | Depending on the risk of frost | In milder climates, full winterisation is not always necessary. Local conditions are the deciding factor. |
These periods are only a guide. Local weather forecasts and conditions on site should always take priority.
Do you maintain several gardens or commercial sites? Plan your inspections in advance, gather information about valve boxes and shut-off points, and check that the systems will be accessible when you arrive. This will help reduce the need for urgent service visits after the first frosts.
What tools and equipment do you need?
The equipment required depends on the drainage method. Before starting work, prepare:
- A system layout plan or list of irrigation zones, along with spanners and screwdrivers for operating valves and fittings.
- A bucket or water container, gloves and labels for components that need to be removed.
- Safety glasses and, when using a compressor, hearing protection.
- If a blow-out is permitted and required: an air compressor with suitable capacity, an air pressure regulator, a pressure gauge, a hose and appropriate connectors.
Not every workshop compressor is suitable for this task. The correct specifications and operating procedure must be determined from the system and equipment documentation.
How to drain an irrigation system: Step-by-step instructions
1. Inspect the system and choose a drainage method
Locate the shut-off valve, valve boxes, irrigation zones, drain points and any equipment where water may remain. Check whether the system has manual or automatic drain valves or whether its design requires a different drainage method. If documentation is unavailable, consult the installer or a service technician. This will help ensure that sections of the system which are not immediately visible are not overlooked.
2. Flush the driplines before shutting off the water supply
Before isolating the water supply, it is worth flushing the driplines in accordance with the manufacturer's recommendations. Open the flushing valves or remove the end caps to clear any accumulated debris. At the same time, check that the emitters are not blocked and inspect the condition of the connections and micro-tubing. This will help identify blocked or damaged components that may need replacing before the next season.
3. Turn off irrigation and isolate the water supply
Once flushing is complete, turn off automatic watering at the controller without losing the existing settings. If you use a temporary watering suspension function, make sure the system will not restart automatically when the specified period ends. Then close the main valve supplying water to the irrigation system and prevent the pump from starting accidentally. Also check the manufacturer's instructions to see whether the controller should remain connected to the power supply over winter.
4. Drain the pipework and use compressed air if necessary
The appropriate drainage method depends on the irrigation system's design. In some systems, opening the drain valves is sufficient. In others, compressed air may be necessary.
Manual drainage
Open the drain valves to allow water to flow freely out of the system. Bear in mind, however, that water may remain in low points in the pipework or in components fitted with check valves. Make sure that all sections requiring protection against frost have been drained.
Automatic drainage
In systems fitted with automatic drain valves, water is released automatically when the pressure drops. However, this does not necessarily mean that the entire system has been drained. Check that no water remains in the main supply pipes or other system components.
Compressed-air blow-out
If the drain valves cannot remove the water effectively, it may be necessary to blow out the system using a compressor. Compressed air pushes water out of the pipework and sprinklers, reducing the risk of frost damage. This method should only be used where permitted by the manufacturer, and the specified pressure limits and safety precautions must be followed.
Safety precautions when blowing out an irrigation system:
- Use a compressor suited to the task and connect it at the designated point. Air should not pass through the pump or the backflow prevention device.
- Before starting the blow-out, open the selected irrigation zone so that water can escape freely through the sprinklers. Work in short bursts, following the manufacturer's recommendations. Once only a fine mist emerges instead of water, stop blowing out that zone. Repeat the process for the remaining zones.
- Always follow safety precautions. Never exceed the permitted pressure, wear safety glasses and do not lean over operating sprinklers or valves. Never leave the compressor unattended.
If you do not have the appropriate equipment or experience, it is best to leave the blow-out procedure to a professional service company.
5. Protect filters, pumps and other equipment
Draining the pipes alone is not enough. Water may also remain in filters, pressure regulators, pumps and other system components. In freezing conditions, this water can turn to ice and damage the equipment.
Make sure these components are drained in accordance with the manufacturers' recommendations. Clean and dry any parts that need to be removed, then store them in a frost-free location. Remember that insulating equipment is not a substitute for draining it.
Also check tap-mounted irrigation timers, sensors and other accessories. Not all components need to be removed for winter, so it is worth checking the instructions for each device beforehand.
6. Record the work completed and plan any necessary repairs
Once the work is finished, record the inspection date, the drainage method used, any damage identified and the components that need replacing. If the system is maintained by an external company, it is worth preparing a brief service report and taking photographs of any equipment that has been removed. This will make it easier to plan repairs, order the necessary parts and restart the system in spring.
What should you pay attention to in a drip irrigation system?
In drip irrigation systems, pay particular attention to driplines, disc filters and pressure regulators. After flushing as described above, clean the filters, check the regulators and drain the equipment in accordance with the manufacturers' recommendations. Remember that insulation alone is not a substitute for drainage, and driplines installed underground are not always protected against freezing.
If you are replacing a damaged section of dripline, make sure its diameter, emitter spacing and emitter flow rate match the rest of the system. You can find more information about the different options in Bosta's guide, ‘Pressure-compensating vs non-compensating dripline: which should you choose?’
Which irrigation system components should you check before winter?
An autumn inspection is a good opportunity to assess the condition of the system and identify damage that could cause problems in the following season. Pay particular attention to:
- Sprinklers – check the housings for cracks and inspect seals and connections for signs of wear.
- Pressure regulators – check the housings and connections for leaks. Make sure they are also properly drained. This applies to regulators such as the Netafim In-line PRV.
- Disc filters – clean the filter elements, inspect the seals and make sure no water remains in the housings.
- Driplines – inspect the condition of the pipes, emitters and connections. Damaged sections should be replaced before the next irrigation season begins.
- Solenoid valves – check the connections for leaks, inspect the condition of the housings and make sure the valves are adequately protected against frost.
If you notice any damaged or worn components during the inspection, make a note of the parts that need replacing. This will make it easier to plan repairs and prepare the system for restarting in spring. Always choose replacement parts that match the specifications of the existing system.
If you are planning to replace solenoid valves, Bosta's guide to choosing the right solenoid valve may also be helpful.
Five mistakes to avoid when winterising an irrigation system
- Starting too late. Overnight frost can occur even when daytime temperatures remain above 0°C.
- Only switching off the controller. This does not remove water from pipes, filters or valves and fittings.
- Overlooking filters or backflow prevention devices. Water can also remain inside their housings.
- Incorrect blow-out procedure. Excessive pressure or forcing air through the system for too long can damage the installation.
- Ignoring the documentation. Different components within the same system may require different methods of frost protection.
Not every irrigation system needs to be blown out using a compressor. The mistake is failing to use the drainage method required for a particular system, rather than simply not carrying out a blow-out.
DIY winterisation or professional servicing?
Preparing a small, familiar irrigation system with a straightforward drainage arrangement may be manageable without professional help. For larger systems, installations without documentation or systems that require a compressed-air blow-out, it is worth considering a professional service.
| DIY maintenance | Professional servicing |
|---|---|
| Lower costs and the flexibility to choose a convenient time. | A drainage method suited to the system and the appropriate equipment. |
| Requires knowledge of the system's design and the manufacturers' recommendations. | Assistance with unusual installations and work involving compressed air. |
| The person carrying out the work is responsible for ensuring it is done correctly and safely. | The work completed and any faults identified can be documented. |
What should you check before restarting the system in spring?
In autumn, prepare a short checklist for the following season. Before switching the irrigation system back on:
- Inspect visible pipework, connections, valves and seals.
- Refit any accessories that were removed and set the drain valves according to the instructions.
- Slowly restore the water supply and check for leaks.
- Flush the system, then test each irrigation zone.
- Adjust the watering schedule to suit the weather and the plants' actual needs.
Repair any faults before regular irrigation resumes. Your earlier notes will make it easier to identify the work required and the parts needed.
FAQ – Frequently asked questions
When should you turn off your irrigation system for winter?
Before the first frost that could damage unprotected components. Night-time temperatures approaching 0°C and forecasts of frost are signs that winter preparation should be completed.
Does every irrigation system need to be blown out with a compressor?
No. If the system is designed to drain effectively through drain valves, a blow-out may not be necessary. The system design and the manufacturer's recommendations are always the deciding factors.
How do you protect driplines during winter?
If flushing is required, carry it out before shutting off the water supply. Then drain the driplines using the method appropriate for the system, and check the filters, pressure regulators and line ends.
Is draining the water enough?
Only if the chosen method ensures that all sections and equipment requiring drainage are properly emptied. Water can remain in low points, filters and valve bodies.
Protect your irrigation system now to avoid problems in spring
Properly winterising an irrigation system helps reduce the risk of damage, additional costs and delays at the start of the next season. It is also a good opportunity to assess component wear and plan any necessary upgrades.
Bosta's range includes Netafim pressure regulators, disc filters and driplines, as well as parts for servicing other system components. Explore Bosta's landscape irrigation range or contact our team if you need help selecting products for a particular system.
