Watering System

An automatic watering system is made up from a number of components, each designed to do a specific job. ISC engineer each system to suit the exact conditions of the site, selecting the equipment that is best suited to the particular installation. The choice and design is founded upon well over twenty years experience in installing and maintaining irrigation systems of all sorts in many countries around the world. Among the variety available, the following are commonly used.

Pop-Up Sprinklers

Pop-up sprinklers are sprinklers which are set into grass or shrub areas lying flush with, or just below, ground level when not in use. When the water is switched on, the sprinkler risers so that the nozzle is clear of the ground, allowing the water to be sprayed over the designed area. When the water supply is turned off, the sprinkler drops back below ground level. On turf, heads with a rise of only 60 - 75 mm. are used whilst heads that rise up to 300 mm. are available for use on areas of shrubs and groundcovers. Various types of sprinkler are available, ranging from fixed head sprays covering only a few metres of giant rotating heads with a range of over 30 M. The majority of garden and landscape systems tend to use relatively small heads (ranging up to a radius of 15 M.) often of the stream spray type which, with a number of rotating jets presents an attractive, as well as effective, watering pattern. Fixed spray heads are available in odd shaped patterns, such as long narrow strips, for particular areas. Pop-up sprinklers have been in manufacturer for a number of decades and have been proven to be exceptionally reliable. They will not interfere with the use of lawn mowers and other garden machinery and games can be played over them. Pop-up sprinklers are, in fact, installed on most major sporting locations including football grounds, cricket squares, race tracks, race courses, etc., as well as golf courses. For very dense or mature areas, shrub-head versions are available for most types of pop-up sprinkler. These do not rise with water pressure but are mounted within the planting, where their location is not at all obvious, on fixed risers. Pop-up sprinklers represent the best of automatic watering technology and as such, as they are fed entirely through underground pipework, they also represent the more expensive end of the list of options available to the irrigation designer.

Micro-Sprays

Micro-sprays are small radius, low flow sprayers or spinners which are not available as pop-up heads but mounted within the planting on small bore polythene risers. They are therefore only suitable for private gardens or landscapes where there is a high degree of security to prevent them being vandalised. This type of spray head can be fed through pipes laid along the ground surface, but hidden within the planting, making for a very economic installation on beds or borders. They are totally un-suited for use on lawns. A pulse jet, ultra-low flow rate version of the microspray is available with the advantage that the standard sized orifice and standard range can be maintained but at a low flow rate down to 2 Lit./Hr. This unit gives a very low application rate and therefore a very gentle and easily controlled precipitation and can be fed from very small bore pipes. The low flow rate (which also selfcompensates for variations in pressure,) allows large areas to be irrigated from a restricted water supply.

Drip Irrigation Equipment

Drip irrigation uses point application devices called emitters which apply water at very low flow rates directly to the soil. As such, they can be used on all forms of planting except turf and, in the context of landscapes and gardens, are particularly useful for irrigating isolated containers and hanging baskets. The emitters are usually fed through small bore polythene tubing laid on the surface and this can be a problem in areas where there is continual replanting where there is a danger of the tube being cut by garden tools. Drip irrigation is probably the most efficient form of irrigation with minimal evaporation and application losses and the ability to apply water very evenly indeed. As there is no overspray onto foliage, drip systems can be also used to apply fertilisers through the irrigation supply. Another form of drip irrigation is based on tapes which incorporate the equivalent of the emitter flow path in the tape structure. The operational life of such systems is usually less than that of an emitter system, but, under certain circumstances this type of system can be buried within the planting beds. If it is buried, care has to be taken with any maintenance tasks carried out on the bed. The main problem with any drip irrigation system is that the flow paths through the emitter or strip are exceptionally small and so the water supply has to be filtered to a very fine degree which adds to the maintenance requirement of the systems.

Water Storage Tanks

If the water supply for an irrigation system is to be the potable mains, then it will be necessary to install a break tank or storage tank between the supply and the irrigation system in order to comply with current By-Laws and regulations. An installed irrigation system cannot be connected directly to a water main. This requirement does not apply when a well, pond or stream is used as the water source, but if the capacity of the well is small then it may be necessary to pump it throughout the day into a tank to feed the night operating watering system. Where a storage tank is necessary, its capacity will depend upon the relationship between the overall demand of the irrigation system, the capacity of the water supply and the peak design demand of the system. Various types and styles of tank are available to suit budgets and the parameters of the site. Tanks can usually be located in an unobtrusive part of the garden or landscape where they can be easily hidden or disguised. In certain circumstances, where the budget allows, the tank can be buried.

Pumping Systems & Controls

Regardless of whether the water source is a well, stream, pond or a tank fed from the mains, it will be necessary to install a small pump unit to provide the pressure necessary to operate the irrigation equipment efficiently. In all but the very largest of schemes, this is likely to be a small single phase unit drawing less power than the average washing machine. On a fully automatic system, the pump unit will be run under the command of the irrigation control panel and fed from a dedicated consumer unit with RCD protection, usually installed by ISC as part of the overall control system. The type of pump used is very quiet in operation which means, in a domestic situation, it can be run in the middle of the night without being in the least obtrusive. An alternative control system, utilising a small pressure vessel, can be used to give a constant supply of pressurised water, on demand, out in the garden or landscape. Thus when any hose point installed on the irrigation system is operated, the pump will automatically switch on. This can be a very useful feature as it can operate, as well as hose points, a high pressure car washing hose, a top-up to a decorative lake or water feature or even to the swimming pool, all from the irrigation supply. On large installations such as commercial landscapes, school playing fields, etc., multiple pump sets are often used along with sophisticated variable speed control systems. ISC designs each pump installation to suit the exact requirements of the individual site.

Filtration

With any drip system a high degree of filtration is essential. Fine filtration of the water supply is also desirable on sprinkler systems. Depending upon the scope of the project and the level of solid debris in the water supply, there is a choice between sand filters, automatic backwashing screen filters, vacuum cleaning screen filters, disc filters, cyclone separators, etc. Often it is necessary for filters to be mounted in tandem. For example, an irrigation system, containing some drip irrigation and fed from a lake might have self cleaning suction filters on the pump intake, automatic backwashing vacuum cleaning screen filters downstream of the pumps and tertiary screen filters in each control valve box, the latter being there to protect the drip equipment from debris in the pipes from the time of installation and debris that will be sucked into the pipes in the event of damage to the mains.

Distribution Pipework

It will be necessary for pipework to be laid around the garden or landscape to feed all the various sections of irrigation equipment. For simple systems on small areas this can often be laid over the surface, concealed in the planting or at the join between a wall and paving, for example, but on most larger gardens it will be necessary to bury pipework, and control cables, throughout the garden. ISC uses plastic pipes for this, uPVC, ABS or MDPE depending upon the conditions on the site, and all manufactured to International Quality Standards. Installing pipework through an existing landscape is a skilled job if the garden is to be put back without detriment and the installation teams of ISC employees (the company does not use self employed sub-contractors,) take all necessary precautions to avoid damage to planting and infrastructure. For example, planks will be laid across lawns to prevent making tracks with barrows, etc., and excavated trench spoil will be laid on woven polypropylene matting to prevent it getting in the surface of undisturbed turf. Good quality turf is stripped by hand and, under normal circumstances, any turf or plants disturbed are reinstated during the same working day. This does slow the work a little, but it makes for a quality job.

Irrigation Control Systems

To make the best of an irrigation system it should be operated automatically and preferably in the middle of the night when evaporation losses will be lowest and there will be no danger of scorching plant foliage. This is also the time when demand on the water distribution system is at its lowest.

A standard irrigation control system comprises low voltage solenoid operated valves installed on each section of the garden or landscape, control cables laid from those valves, with the distribution pipework, back to the controller and the irrigation controller itself. The solenoid valves, which operate at only 24 Volts, are usually installed in small green chambers located in soft areas. Every effort is made to keep these out of lawns and amongst over hanging planting so that they remain unobtrusive.

A properly installed watering system is all but invisible. Control cables are usually specified with a Hy-Tuf outer sheath so that they are not damaged if accidentally struck by garden tools. Even the simplest controllers allow each solenoid valve to be individually timed so that variations in the type of planting, or other such factors as aspect and shading, can be taken into account in setting the amount of water applied. For example, a fully exposed lawn on a gentle south facing slope will require more water than an area of herbaceous planting partially shaded by trees and it is important that the design of the irrigation system reflects this and that it is taken into account when setting the operating times.

Quite simple controllers can also allow each section of the garden or landscape to be assigned to either of two different irrigation cycles so that, for example, lawns may be watered once every two or three days, whilst containers and hanging baskets are watered up to three times a day. This type of facility is very helpful in making efficient use of water resources. Controllers can be fitted with a simple rain switch which will prevent watering taking place during and immediately after any summer rain and more sophisticated soil moisture sensors can be used to measure available soil water and control the irrigation system with a view to maintaining it between certain limits. On very large systems full computer control with automatic daily updating from a dedicated weather station can be used to optimise the amount of water consumed.