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How to Install an Underground Sprinkler System

How to Install a Sprinkler Irrigation System

A complete guide to all the pre-installation steps before the sprinklers are installed. In this guide, learn how to supply an underground sprinkler system, wire a solenoid valve and combine components inside the valve box for the system to function optimally. This guide also takes you through step by step, how to connect your solenoid valves to an irrigation controller and how to program the controller to suit your watering requirements.

Supplying a Large Underground Irrigation System

Water that supplies a small pop up sprinkler system can be sourced directly from an outside tap however, larger and more permanent systems require water obtained from the mains water pipe that delivers water to your home.

Important Note: Supplying water to an underground sprinkler system requires the expertise of a professional. Due to rules and regulations regarding the protection of mains waterways, it is a task that should warrant help from a plumber.

The professional will tap into the smaller capacity pipe that tapers water off to your home from the mains water supply using a Compression Tee Fitting. Before starting any work or tapping into the pipes, the water supply should be shut off at the water metre.

Top Tip: Don’t forget to use Pipe Inserts that line the inside of MDPE or HDPE pipe to prevent buckling under the compressive pressure of a fitting. 

A Stop Tap Connector should then be installed after the Tee Fitting so the water supply to your irrigation system can be switched off independently from your home. After this step has been completed the water supply can be restored back to your home. This is ideal for system maintenance or when carrying out any repairs. For ease of accessibility, install the stop tap connection inside a Valve Box.

Also inside this valve box, you will require a drain valve placed after the stop tap to allow the release of any trapped water during the winter months or when carrying out maintenance. The next and one of the most important installation stages is to connect a Backflow Prevention Device. This vital device should also be installed by a professional and functions to protect potable water within the main supply from contamination. You will be required to consult building regulations codes within your area before installation.

Irrigation System Connected to the Water Main

Supplying a Small Underground Sprinkler System

Smaller domestic underground irrigation systems can be supplied via an outside tap and still be controlled automatically. Begin by accurately measuring around the perimeter of where watering will take place and create a scale drawing of the location of the house, significant obstacles such as trees and patios and where you would like the sprinklers to water. You may also wish to take note of times of the day when areas in the garden are in sun or shade as this will impact watering requirements. Please Note: A Backflow Prevention Device is required to protect your water source from contamination. For more information, read our guide to protecting your water source.

Installation Method 1

1. For larger, more robust and automated systems that incorporate an Irrigation Controller and Solenoids, use MDPE/HDPE pipe and Compression Fittings at each connection point.

Installation Method 2

2. For a small irrigation system controlled by a Water Timer, the system can be connected using LDPE Pipe and Barbed connectors making sure to use a Ratchet Clamp at every connection point.

How a Solenoid Valve Works

1. Water flows into the inlet via the valve body. 

2. Water fills the bonnet chamber. At this point, the water pressure pushing on the internal diaphragm keeps the valve closed.

3. The water continues to flow towards the solenoid chamber located just below the solenoid.

4. As communications from the controller are received,  the coil within the solenoid becomes electrically magnetised lifting the solenoid plunger.

5. The water underneath the diaphragm now has enough pressure to open the valve.

6. Water then flows freely through the outlet of the solenoid towards the sprinklers.

7. Once communication to the solenoid stops, the solenoid plunger drops back down inside the chamber stopping water flow.

8. The force acting above the diaphragm closes the valve and stops water flow to the sprinklers.

Why Use a Solenoid Valve?

A solenoid valve receives electrical communications from the irrigation controller and functions to split Pop-up Sprinklers, Rotors, Bubblers and Drip Line into separate irrigation zones. As electrical signals are received by the controller the valve opens and supplies water to operate the sprinklers. It is important to split an irrigation system into zones as most gardens require multiple emitters and sprinklers that will exceed the available water/flow rate from your tap/water source at any one time. Successfully zoning a system will ensure emitters operate at their optimal level and water can reach the farthest point away from the water source.

Top Tip: Zoning a system means you can run a sprinkler system from one zone and Drip Line from another. To ensure accurate and uniform distribution of water, it is important not to mix types of emitters or sprinklers with different performance statistics or from different brands.

Where to Install a Solenoid Valve in a Sprinkler System

A solenoid valve should be installed upright within a Valve Box and as close to the Irrigation Controller as possible.

ldpe pipe

This reduces the requirement for long passages of electrical wire and enhances the solenoid's ability to receive communications from the controller. Connect multiple valves using a Manifold making sure to properly install the solenoid following the arrows that indicate the flow of water.

manifold

Top Tip: For reliable and watertight connections, wrap PTFE tape around any male threads. Use an O-Ring supplied with HydroSure Manifolds to secure any female connections.

To promote the longevity of a solenoid valve and the rest of your system, install a Filter to the lateral pipe supplying the manifold.

filter

This reduces the build-up of sediment and particles that will clog vital components and hinder their performance. When installing a filter, ensure the directional arrow printed on the filter mirrors the direction of water flow.

After the solenoid valve has been installed, a Pressure Regulator can be directly attached the valve downstream of water flow.

solenoid and pressure

Ensuring water pressure is regulated to the correct level (around 3-6 Bar for a sprinkler system and 1-3 bar for a micro-system) means components can function optimally. Top Tip: Use Threaded Sockets and Adaptors to connect components with non-compatible threads.

solenoid in valve box

A Valve Box should be installed below the surface. To install, begin by digging a hole 12 inches wider and longer than the valve box to allow for installation of lateral pipe and fittings.

To protect against weed penetration, coat the floor of the box with a permeable membrane that allows water to drain away followed by a layer of gravel to maximise drainage. The base of the box should also be mounted on top of bricks to minimise sinking. Taking these steps ensures vital components within the valve box are easily accessible and are protected from water damage. 

Depending on seasonality and weather conditions, an irrigation system usually is drained down and switched off by mid-October and switched back on in early Spring. As the system is switched off, water will naturally drain back to the solenoid valves. It is important to use a manual valve that can be left open over the winter months to allow any sitting water to escape. Installing a drain valve at the lowest point of a system will also prevent damage from sitting water. In spring, when the system is ready to be switched back on, any build-up of mud within the valve box should be dug out and the solenoids wiped over with a damp cloth.

Wiring a Solenoid Valve for a Sprinkler System

1. Before wiring the valve, be sure to tighten the solenoid into the valve by hand only. It is important not to over tighten!

tightening a solenoid valve
solenoid wires

2. Take one wire from each solenoid, it doesn’t matter which as the wires are non-polarised. These wires will connect all the solenoid valves to the same wire, usually called the common/white wire. Creating a circuit connection between all the valves in the system ensures the valves can communicate and switch on/off at different times.

3. If using only two solenoid valves in a system, install the end of the selected wires from both solenoids and the common wire into a jelly crimp. If using more than two solenoid valves in your system, circuit the wires using two jelly crimps and a separate piece of wire to join the two jelly crimps. The solenoid wires and common wires can be installed to the remaining outlets on the jelly crimp.

wiring a solenoid valve

Top Tip: Ensure no exposed copper wiring is situated outside a grease-filled plug as this can cause electrical shortages and problems with your system.

4. Next, we will take the second wire on the solenoid valve not connected to the common wire and connect this to the wire that will lead to the controller. For each valve, select any colour wire from the electrical cable and assign this colour to a single valve. Make a note of which colour a valve is assigned to for ease of zone identification.

Wiring a Solenoid Valve
solenoid wires

4. To connect the valve to the controller, take your chosen colour wire and the remaining solenoid wire and install both into a jelly crimp. Repeat this process for each valve, assigning a new colour wire per valve. Any wires not required should simply remain where they are in case of system expansion.

5. Place the wires in a waterproof length of pipe to protect them against damage from rain or freezing temperatures. This length of pipe encasing the wires will transport the electrical cable from the solenoid valves to the irrigation controller. Top Tip: If possible, use the same trench for the wires as the lateral pipe and tape the water and electrical pipe together for ease and to minimise installation costs and labour.

Wiring a Solenoid Valve

How to Install a Valve Box

A valve box is designed to provide protection and easy access to solenoid valves, stop taps, filters and drain valves etc. Once installed, simply lift the lid on the valve box to access the internal components – ideal for system drainage during the winter months or manual system applications.

Irrigation Valve Box

To Install

1. Dig a hole to accommodate the size of the box plus room on either side for connectors and pipework.
2. Level off the ground and check that the valve box will fit flush to the surface level.
3. Install a layer of permeable root matting to prevent root intrusion.
4. Place a layer of gravel over the top of the root matting to aid drainage.
5. Install components inside and check the system is in full working order before filling in the soil around the sides.

Top Tip: Make a note of where the valve box is located for easy reference when you need to carry out system maintenance.

Automated Sprinkler Irrigation

Irrigation controllers require AC power to prompt the sprinklers to water. The connection between the controller, solenoids and your household mains power supply should be carried out by a licenced professional. 

Why Use an Irrigation Controller?

Using a controller to operate an irrigation system removes any requirement for taking time to manually water your garden. Without a controller, you would need to manually turn on/off a solenoid valve each time you wish to water – a time consuming task!

How to Wire an Irrigation Controller

As previously seen in the ‘Wiring a Solenoid Valve’ section of this guide, the electrical wire is safely transported to the irrigation controller via a length of waterproof pipe taking the shortest and most direct route. The solenoids can now be connected to the controller to create a circuit that can successfully communicate and operate the sprinklers/emitters.

Begin by connecting the common/white wire, linking the solenoids to the ‘C’ terminal on the controller and tighten down with a screwdriver. Repeat the same process with the remaining wires connecting the wires from the solenoids to a terminal. The colours assigned to the solenoid valves can be connected via your chosen zone usually marked 1,2,3,4 and so on. Isolating the valves per terminal allows each valve to be operated individually.

Test the system by switching on the controller and independently running station by station. The valves should make a humming noise if they are installed correctly. Most Irrigation Controllers arrive with an operation manual which can seem quite daunting at first but, it is worth taking the time to read through and fully understand your controller in order to create a fully automated irrigation system requiring minimal input or maintenance.

How to Program an Irrigation Controller

1. Begin by switching the controller on via the mains socket. It is important to install your controller near a plug socket for ease of access. Some controllers have a backup system or are entirely battery operated and have a 9 Volt battery port.

Twist the dial on the controller to point to the below applications.

2. Most controllers require you to set the date and time. It is important to enter this information accurately to ensure the dates and times the controller is set to water are correct.

3. Next, set the program start times. To conserve water and minimise water runoff, create multiple start times per zone. For example, a zone may be watered for a total of 30 minutes but is split into three 10 minute cycles. The controller will move to the next zone for 10 minutes and so on.

Top Tip: Set start times to water early in the morning or late in the evening to minimise water loss through evaporation in the midday sun.

4. Set the days you wish to water and for how long. It is advisable not to water plants every day as this can hinder root growth and promote disease. Water less frequently and for longer to allow water to seep into the ground which in turn, encourages deeper root growth and healthier plants.

5. Often controllers arrive complete with a percentage feature also known as a seasonal functionality feature. This allows for customisable watering during the Autumn/Winter months by reducing the run time, and therefore water, that emits into each zone. During the spring/summer months, the percentage can be increased.

Irrigation Sensors

For ultimate water conservation and plant health, install a Rain Sensor that works alongside your controller. This works by sensing moisture or rain in the air to temporarily suspend watering during wet weather. Compatible controllers have a terminal readily available for connection to the rain sensor.

Planning an Underground Sprinkler Irrigation System

Before planning a sprinkler system, it is important to calculate the rate of flow water outputs from your tap, also known as the flow rate. Using this knowledge, it is easy to calculate how many pop-up sprinklers can be run directly from your tap. For more information on how to calculate flow rate and zoning a sprinkler system, Read our Guide. It is also helpful to plan where to position components using graph paper to sketch a plan of your garden. 

Click Here For Graph Paper - 1cm x 1cm

For further information on how to install Pop Up Sprinklers and Rotors including how to achieve head-to-head watering and calculate sprinkler run times, read our Sprinkler Guides.

Frequently Asked Questions

Important Note: Due to the nature of how solenoid valves are linked to mains power, consult a licensed professional before carrying out maintenance. 

sprinklerfaq

Which Solenoid Valve do I Need?

If using a 9V/Battery Operated Controller, use it alongside a 9V DC Solenoid Valve to ensure the current is enough to operate the valve. 9V DC Solenoids operate on a lower voltage and have much smaller coils inside the solenoid so should not be used alongside mains powered controllers.

When using a 24V Mains Powered Controller, install it with a 24V Solenoid to ensure the inrush current does not destroy the solenoid coils.

Top Tip: Contact a qualified electrician before purchasing and installing your components.

sprinklerfaq

Why is my Solenoid Valve not Working?

A solenoid valve that does not open or shut off water flow when required or is leaking indicates damage to the solenoid or valve. After switching off the water flow and power supply linked to the valve, check the following considerations are met.

1. Debris built up inside the valve’s internal mechanisms may be causing a blockage or preventing the valve diaphragm from operating as it should. Ensure the valve box is free from any dirt or weed growth clogging any vital mechanisms.
2. Check the water pressure and flow rate from the water source to the valve are within the range outlined in the product’s specifications. Too much pressure will cause damage and too little will prevent the valve from opening. 
3. A valve may be prone to leaks if the O-ring between the solenoid thread and solenoid port is bent, twisted or perished. Turn your valve to the off position before installing a Replacement Solenoid.

sprinklerfaq

Irrigation Solenoid Valve Remaining Open

1. A valve that won’t shut off indicates a problem with the internal plunger where the port has become blocked or filled with debris preventing the plunger from dropping down into the valve. Often cleaning the solenoid port should rectify this problem. After cleaning the solenoid port, switch the solenoid valve off manually or at the controller level. If the valve remains open, the internal mechanisms will need inspecting and further cleaning.

2. For valves with built-in flow control, turn the flow control down until the valve does eventually close (usually this is achieved by turning in a clockwise direction). Once you have established the required level of flow, leave the flow control in this position. This should allow the valve to work correctly opening automatically when receiving communication from the timer.

sprinklerfaq

Are Solenoid Irrigation Valves Waterproof?

A solenoid valve should be installed in a dry Valve Box with adequate drainage that is not prone to flooding. This is to maintain the integrity of the valve over time protecting against the effect of thawing and freezing and the risk of electrical wires getting wet. Solenoid valves are designed to cope with some immersion of water, however, they should not be submerged for long periods. HydroSure Solenoid Valves are epoxy encapsulated and designed for maximum moisture resistance and longevity compared with moulded solenoids. Please Note: All electrical wires should be encased in a waterproof Jelly Crimp with no exposed wiring – Consult a licenced professional during installation.

sprinklerfaq

How to Replace a Solenoid Valve

The solenoid and solenoid valve are separate components. If the valve is not damaged, you can simply replace the solenoid.

1. Begin by shutting off any water/power supply to the valve.
2. The wires connecting the old solenoid to the system should be cut off at the connection point making sure to save as much wire as possible that connects to the system but dis-guarding any wire that has corroded or split.
3. Unthread the solenoid from the valve by turning the solenoid counter-clockwise. Once the old solenoid is removed, clean the solenoid port on the valve before installing the new Replacement Solenoid.
4. The new solenoid can be threaded into the solenoid port and rewired to the common wire and zone it controls. Ensure no copper wiring is exposed and each connection is secured using a Jelly Crimp.

Top Tip: During this installation, take care not to get any dirt in the solenoid ports or cross-thread the solenoid which will hinder its function.

sprinklerfaq

Irrigation Solenoid Valve not Opening

1. Check the water supply is switched on and there are no flow restrictions such as a closed valve or a leaking connector.
2. If using a valve with built-in flow control, ensure the valve is not closed/partially closed preventing water from reaching the sprinklers.

3. Most solenoid valves allow you to remove the valve bonnet. Before undertaking any maintenance, turn off the water supply to your valve box and drain the irrigation line. Then, remove the solenoid lid by unthreading the screws. Check if any grit or large particles have become lodged inside. The debris can be removed or flushed from the valve and the lid refitted.

4. A low flow rate or low pressure generated from the tap can cause a valve to remain closed. To combat this, manually open the valve using the bleed screw to allow water to run through. If the valve remains closed, this indicates an electrical problem and it is advisable to contact a licenced professional to carry out maintenance.