Maintenance and Winterization of Irrigation System

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Winterization and maintenance of an irrigation system – a complete guide for every gardener

Autumn is approaching, temperatures are dropping, and you are asking yourself what to do with the whole system of pipes, sprinklers and valve blocks that you have been building or using all summer. If you left the irrigation "for later" and frost caught your plans, you know well the damage that frozen water can cause in plastic pipes or in the body of an electromagnet valve. From practice, I can say that in every tenth job in March we deal with cracked PE pipes, shattered ball valves or destroyed solenoid valves – and it is always the result of neglected winter shutdown. This article is about how to avoid this, but also about what to do throughout the season so that the system works reliably year after year.

This topic is related to other articles in our Knowledge Center – if you have not yet designed your system, see the article How to design irrigation zones for a garden, lawn and flowerbed, or if you are dealing with a specific problem after winter, I recommend the article Common irrigation system faults and their repair. Winterization is a chapter in itself and deserves a detailed explanation.

Why winterizing an irrigation system is so critical

Water expands by about 9% when it freezes. This may sound modest, but in a closed pipe with a diameter of 25 mm and a length of several meters, it creates enormous pressure – commonly given as around 25 to 170 MPa depending on the conditions. Even the strongest PE-HD or PP pipe system cannot withstand such pressure. Especially sensitive are joints, T-pieces, elbows and, above all, thin-walled parts of sprinklers, drip emitters and solenoid valves.

A common mistake we see with customers is the belief that "we don't have big winters here". In the lowlands of central Slovakia, where it seems that temperatures rarely drop below −5 °C, the system survives the first winter without problems. Then comes January with three weeks below −10 °C and the damage is total. Also, be careful in spring – night frosts in April can destroy a system that you have started too early.

When to start autumn maintenance and winterization

The recommended time for most locations in Slovakia is the end of September to mid-October. It depends on the altitude – in mountainous areas above 600 m a.s.l., you can start as early as mid-September, in the Danubian Lowland you may wait until the end of October. As a general guideline, it is time when the average night temperature regularly drops below +5 °C.

Never wait for the first frost as a signal – it is usually too late, or you have only a few hours, which is stressful. You can turn off the system and shut it down calmly in one afternoon if you are prepared. We do it in order: stop irrigation, turn off the control units, drain the water, shut off the valves, check the sprinklers and protect sensitive parts.

Approximate schedule for autumn maintenance

2 weeks before shutdown: Visual inspection of the system – check all sprinklers, possible leaks, function of solenoid valves. Repair minor faults while the system is still in operation and you can easily see what is not working.
1 week before shutdown: Order or prepare a compressor (if you are doing air blowing), check if you have prepared the caps and protective covers for the sprinklers.
Day of shutdown: Turn off the main supply, manually run each zone, apply compressed air, close the valves, store the sensors and control units.
Day after shutdown: Final inspection – check if there is no dripping anywhere, all taps are closed, covers are in place.

Three methods of draining water from the system

There are three basic approaches to draining an irrigation system. Each has its advantages and limitations and the choice depends on the topography of the garden, the construction of the system and your technical possibilities.

1. Gravity drainage (passive method)

This only works if the entire distribution is designed with an appropriate slope towards the drainage points and automatic or manual drain valves are installed at the lowest points. Practice shows that this solution is reliable only in gardens with a height difference of at least 30–50 cm between the highest and lowest points of the distribution. In a flat garden, gravity is not enough – water puddles will remain in the pipes and freeze.

Procedure: Close the main supply, open the drain valves (usually at the end of each branch) and let the water drain. The drainage time depends on the volume of the system – in an extensive distribution with a total length of 200–300 m of pipes, it can be 10–20 liters of water. The whole process takes 15–30 minutes. After drainage, leave the valves open throughout the winter or close them if you are sure the system is empty.

2. Manual drainage using air vents

In this method, you go step by step from the main distribution through each zone and manually open the air vents or manual valves at the ends of the branches. It is more laborious, but quite reliable in a well-designed system. The disadvantage is that in T-pieces and horizontal sections, water may remain in the lowest places without an obvious outlet.

3. Blowing out with compressed air (blow-out method) – the gold standard

This is the method that is used by the vast majority of professional installers today and we recommend it for home use in larger systems. The compressor is connected to the main pipe via a special quick-connect input or directly via a Schrader valve (bicycle type), which can be added to the distribution during installation. The pressure must be set correctly – too low will not push out the water, too high can damage the pipes or sprinklers.

Blow-out procedure step by step:

Close the main water supply to the system.
Set the compressor pressure to a value corresponding to the pipe diameter – usually 2–3.5 bar for standard PE pipes. Never exceed 4 bar.
Manually activate the first zone (either through the controller in manual mode or directly at the solenoid valve by manually opening the bleed screw hole).
Connect the compressor and let the air circulate through the system for 2–3 minutes, until only dry air without water comes out of the sprinklers.
Repeat for each zone separately.
You may repeat the procedure 2–3 times for each zone if the system is complex or large.
After completion, leave the manual valves on the solenoids in the open/neutral position, so that any residual water can escape.

Warning: Never stand over a sprinkler during blow-out – the pressure can shoot it out of the grass into the air. Also, never blow out the system without an active open zone – the air must have an escape route, otherwise pressure will build up and damage components.

Solenoid valves – require special attention

Electromagnetic (solenoid) valves are the most sensitive part of the entire system. The valve body is usually made of plastic (PVC, polyamide), but the membrane, spring, and coil are stressed by frozen water pressure just like anywhere else. Moreover, a cracked plastic body of a solenoid valve is an expensive repair – a new 1" valve typically costs 15–40 €.

When it comes to valve boxes, follow these rules:

All solenoid valves must be installed in boxes (VALVE BOX type), which provide some thermal insulation, but not full frost resistance.
If the valves are installed in shallow boxes (less than 30 cm depth), protect them with insulation in freezing conditions after shutdown – a simple EPS board or mineral wool inserted into the box is sufficient.
Turn the manual bleed screw on the solenoid valve 1/4 turn to the left after shutdown – this allows residual water to drain from the valve body.
Disconnect the electrical connectors from the solenoids if the system in the box is exposed to moisture. Moisture in the contacts causes corrosion and problems when starting the system in spring.

Controller, sensors and electrical installation

The controller (irrigation programmer/timer) is the brain of the system. Most modern units are designed for installation in an outdoor, but sheltered, not heated area – garage, covered garden shed, or a porch. At temperatures below −20 °C, the display may change contrast and the backup battery (for power outages) may lose capacity. Nevertheless, the electronics itself usually survives the cold, provided it is not exposed to moisture.

Our recommendations for winter:

Backup battery: Check the battery (usually 9V or AA) before winter and replace it if necessary. After winter, when you restart the system, you will find the program preserved.
Soil moisture sensor: A sensor buried in the ground may crack during freezing if it is not certified for winter operation. Remove and store the sensor indoors.
Rain sensor: This usually stays outdoors, but check if the sensor housing is cracked from the previous winter. This does not matter in winter, but after thawing it may short-circuit.
Cable installation: Inspect the cables from the controller to the solenoid valves – if you have noticed any digging, pets, or garden tools in the area, check the insulation integrity.
Main system switch: Switch the controller to the "Rain" or "OFF" position (not a complete power disconnection, if the unit requires backup power to retain the program).

Sprinklers and nozzles – inspection before and after winter

The sprinkler is a component people often forget about until it starts spraying in the wrong direction or not at all. During winterization, focus on the following:

Before shutdown (autumn)

Inspect all sprinklers in your lawn/bed. Repair any that do not pop up or spray at the wrong angle now – check the nozzle insert and filter (a small mesh inside the sprinkler body).
Remove and store indoors all sprinklers that are above ground level (i.e., fixed top outlets on stakes near shrubs). The plastic body may crack even in light frost if it is flooded.
Pop-up (riser) sprinklers embedded in the lawn survive frost better – they are below the surface. However, even here it applies: if you performed a blow-out, water should not remain.

After winter (spring) – starting the system

Before turning on the main water supply, open the manual drain valves at the ends of the branches. Let water slowly fill the system to avoid water hammer (hydraulic shock).
Open the main shut-off valve gradually – not all the way at once.
Activate each zone manually and observe the sprinklers: correct range, correct angle, no missing nozzles.
Check the solenoid valves – whether they open and close correctly. For help, refer to the article Common irrigation system faults and their repair.

Seasonal maintenance – what to do during summer

Winterization is important, but you don’t have to wait until autumn to take care of the system. A system that receives regular attention during the season will last much longer and save you money and nerves.

Monthly checks during the season

April – May (start-up): Inspection of the entire system after winter, setting up programs, checking pressure (if you have a pressure gauge, compare the measured pressure with the values in the article What pressure and flow do I need for irrigation?).

June – July (peak season): Visual inspection every 2 weeks. Look for sprinklers spraying sideways (broken nozzle or sand in the filter), drip emitters clogged (reduced flow in drip lines), and areas where grass or plants are wilting despite irrigation (poor coverage, clogged nozzles).

August (seasonal preparation): Final inspection, order replacement nozzles, filters and other consumables if you notice signs of wear. Also check the garden pump station, if it is part of the system – see related topics in the Home water supply and filtration section.

Filtration – the most commonly neglected component

Every irrigation system should have a mesh filter (disk filter or mesh filter with a fineness of 100–200 mesh) installed at the inlet behind the main shut-off valve. This filter captures impurities from the well or public water supply that would otherwise clog the nozzles and drip emitters.

Clean the filter at least once a month during the season, and every two weeks if using well water. The procedure is simple: shut off the water supply, unscrew the filter lid, remove the screen, rinse it under running water, and put it back in. The whole process takes 5 minutes. A neglected filter reduces system pressure, which has a cascading effect on all zones.

Drip irrigation – special requirements for winter

Drip systems have some differences compared to sprinkler systems that need to be considered during winterization. Drip lines (hoses with integrated emitters of 16 mm or 20 mm diameter) are more sensitive to mechanical damage in freezing conditions if they remain filled with water and are exposed to frost on the ground surface.

At the same time, the pressures in drip systems are lower (typically 1–2 bar), so gravity drainage may work better than in high-pressure sprinkler systems. Nevertheless:

Drip lines buried under mulch or covered with soil can survive the winter without disassembly – mulch and soil provide sufficient protection.
Drip lines on the surface (e.g., in flower beds, where they were laid on top of mulch) should be coiled up and stored in an area that does not freeze.
Start connectors, T-pieces and push-fit fittings should be removed from the line and stored – they are extremely fragile at low temperatures.
Pressure-reducing valves for drip systems should be removed and stored indoors.

If you are interested in a comparison of drip and sprinkler irrigation systems in terms of advantages and disadvantages, I recommend reading the article Drip vs. Sprinkler Irrigation – What is better for your type of garden.

Irrigation from a well or rainwater tank

If your irrigation system uses a submersible pump in a well or a surface pump station, winterization also involves taking care of these components. This topic is covered in detail in the article Irrigation with recycled rainwater – what you need to know, but the basic principles are:

Surface pump station: Turn it off, drain the water from the pump body (usually via a bottom drain valve) and store it in an area that does not freeze. A surface pump station in an unheated garden shed at −20 °C will not survive.
Submersible pump in a well: The pump itself is protected while submerged in water, but the suction and discharge piping above ground must be drained. Check the check valves – if they are not tight, water will drain back into the well during winter and the pump will need to be vented when starting in spring.
Rainwater tank: Drain above-ground tanks or fill them only two-thirds full so that expanding ice does not damage the walls. Underground concrete tanks are frost-resistant, but the inlet and outlet piping must be drained.

Most common mistakes during winterization – from real-life experience

Over the years in this industry, we have seen dozens of the same mistakes. Here are the most common ones:

Incomplete blowing out: The customer blew out the system but forgot one zone or a dead-end branch. The result in spring: one burst pipe and a flooded manhole.
Early spring startup: "It was 15 °C, so we turned it on." April night frosts are dangerous. We recommend waiting until night temperatures consistently stay above +3 °C for at least two weeks.
Forgotten manual valve on the inlet: The system was blown out, but the main shut-off valve was left open. Water from the public water supply slowly returned into the system through the check valve seal. In spring, the pipe was full of water and frozen.
Ignoring surface lines: Sprinklers turned off, drip lines above ground left without disassembly.
Unsecured manhole: The valve box lid was broken, water entered the manhole during winter snowmelt, and the solenoid valve was submerged in water.
Compressor pressure too high: The customer set it to 6 bar "to clean it thoroughly". The result: 3 burst sprinklers, 1 destroyed solenoid valve.

Complete autumn inspection checklist

☐ Turn off the irrigation in the control unit (position OFF/Rain)
☐ Close the main shut-off valve for water supply to the system
☐ Blow out each zone with compressed air (2–3 cycles of 2 minutes each)
☐ Check that dry air is coming out of each sprinkler
☐ Open the manual air vent on each solenoid valve (1/4 turn)
☐ Disconnect the electrical connectors of the solenoids or check the seals
☐ Insert EPS insulation into the valve boxes
☐ Check/replace the battery in the control unit
☐ Remove and store the soil moisture sensor (if installed)
☐ Remove and store surface drip lines and connectors
☐ Drain/store the surface pump or pumping station
☐ Check rainwater tanks and their inlet pipes
☐ Document the system condition (photo from the phone) for spring
☐ Order spare parts that will be needed in spring

Spring system startup – as important as winterization

Proper startup after winter is just as important as proper winterization. Suddenly filling the system with water from a closed state can cause a hydraulic shock (water hammer), which can damage connections or valves. Procedure:

Visual inspection of the entire pipe network before startup – look for visible damage.
Close all manual end valves (if you opened them for winter).
Open the main shut-off valve only 1/4 turn and let the system fill slowly for 5–10 minutes.
Gradually open the shut-off valve fully.
Manually activate each zone and check the sprinklers and solenoid valves.
Set and check the control unit program – surprisingly many customers find out that the program is erased or incorrect.
Set the pressure and check the filter.
Plan the first real irrigation for a day when you are at home – this way you will quickly detect any problems.

We recommend reading the article Installation of an automatic irrigation system step by step for proper setting of the program and zones, where the principles of setting timers and zones are described in detail.

Lifespan of components and when to plan replacement

A good irrigation system should work for 10–15 years without major problems if properly maintained. In practice, however, some components have a shorter lifespan:

Diaphragm seals of solenoid valves: 5–8 years with regular use. A signal for replacement is when the valve leaks even in the closed position (drips).
Sprinkler nozzles: 5–10 years, shorter in sandy water. Worn nozzles spray irregularly or with less reach.
Drip emitters: 3–7 years, depending on water quality and filtration.
PE pipes: If properly buried in a non-freezing depth (min. 30–40 cm), they can last 20–30 years. Surface PE hoses (16 mm drip lines) last 5–10 years.
Control units: Electronics usually last 8–12 years, after which problems with the display or programming may occur.
Control unit battery: Replace every year without exception – a cheap prevention.

Most frequently asked questions (FAQ)

When is the most accurate time to winterize an irrigation system in Slovakia?

For most locations, it is from the end of September to mid-October. In the Danubian Lowland (Bratislava, Komárno, Dunajská Streda), you can wait until the end of October if the forecast does not predict frost. In mountainous areas (Banská Bystrica, Žilina, areas near mountains), it is better to start already in the first half of September. Reliably follow this: when night temperatures regularly drop below +4 °C, it is time.

Do I have to do a blow-out with a compressor every year, or is gravity draining enough?

It depends on the topography of the garden and the system design. If the garden is sloped, all pipes are laid with a slope towards the drainage points and you have a functional air vent at the end of each branch, gravity draining may be sufficient. For a flat garden, a more complex layout, or when using a well with horizontal pipe sections, we recommend blowing out with a compressor. If you are unsure, better invest an hour with the compressor – it is a cheaper alternative to repairing a cracked pipe in January.

Can I leave the control unit outside during winter?

Most modern control units (timers) are designed for installation in a protected exterior – covered but not heated space. Continuous temperatures below −15 °C can damage the LCD display or the backup battery. If the unit is exposed to direct frost and moisture, we recommend disconnecting it and storing it indoors during winter. The program will remain in memory if it is equipped with a backup battery and you replace it with a new one before storage.

I forgot to winterize and the system froze – what now?

Do not wait for thawing and immediately close the main water supply. After complete thawing (not before!), slowly open the supply and check each zone. Look for: wet spots in the lawn (cracked pipe underground), non-functional sprinklers (cracked body), leaking solenoid valves. Most damage can be repaired by replacing the damaged components. Cracked PE pipes can be repaired with coupling clamps without excavation (if the damage is localized). Details can be found in the article Common irrigation system faults and their repair.

Is it necessary to winterize drip irrigation in a greenhouse or polytunnel?

If the greenhouse or polytunnel is heated during winter and the temperature does not drop below +2 °C, winterization is not necessary – the system can be left in operation or simply turned off without blowing out. If the greenhouse is unheated in winter and frost penetrates inside, the same rules apply as for an outdoor system – that is, complete draining or blowing out. Be careful with the main water supply from the outdoor network – it must definitely be winterized regardless of the greenhouse.

Can I borrow a compressor for blow-out, or do I have to buy one?

By no means do you have to buy it if you use it once a year. Most gardeners borrow it from neighbors, rent it from a tool rental shop (price usually 5–15 €/day), or agree with an installer who will perform the entire blow-out for a one-time service fee. For a larger system (more than 5 zones, 25 mm and larger pipes), we recommend a more powerful compressor with a tank volume of at least 50 liters – cheap small compressors with a 6–10 liter tank may not have enough air volume for reliable blowing out of a long branch.

Conclusion – maintenance that pays off

An irrigation system is an investment that pays off only if it is properly maintained. Year-round care – from spring startup through summer checks to autumn winterization – extends the system's lifespan by years, saves water (a well-maintained system without leaks and clogged nozzles is significantly more efficient) and protects you from unpleasant and expensive repairs. If you are planning a new system or expanding an existing one, also check out other topics in our Knowledge Center – for example, How to save water in garden irrigation or How to choose the right irrigation system for your garden. The entire irrigation range can be found in the relevant category, where components for each phase of installation and maintenance are available.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.