Choosing a system

Drip Irrigation

This is traditionally the application of a constant steady flow of water to soil at low pressure. A series of tubes is placed either just above the soil surface, preferably below the leaf canopy of any plants, or in the soil itself at or above root level. Water loss is minimised through these measures as there is very little splash owing to the low pressure and short distance to the ground. Reduced splash increases the amount of water which reaches the desired area of soil and means there is less opportunity for evaporation to take place directly into the air. The purpose of the leaf canopy is to capture as much light as possible while minimising the amount of rain or moisture which is directed horizontally away from the plant roots. It is best therefore in terms of water conservation to set any irrigation system below this level.

Burying the drip system is reduces water loss even further by preventing run off across the surface, which can occur at very high rates on dry impervious ground. It also reduces the chance of damaging the system while weeding. The soil surface is also kept dry which can reduce invasion by weeds. Some chemical insecticides and fertilisers are most efficiently applied via a drip irrigation system in terms of timing and precision of amounts to be used. This can lead to significant savings in money and maintenance time of the garden, care must be taken to ensure that the product is suitable for this type of application and will not damage the irrigation system.

There are many different manufacturers of the system components each with a vast range of products. One of the main factors that varies between systems is the emission device. This is point where water is released and can affect the amount of water released and the flow rate. A good company will explain the differences between the products and help you to choose the most suitable. It is very important that the correct sized valves, emission devices and diaphragms are used for the system to be efficient. Hydraulic calculations must be made to make these decisions so you should ask the company to show you their workings even though you are unlikely to understand them. If the person you are dealing with looks completely flummoxed, it could be a sign that they are not as qualified as they'd had you believe.

To maximise the effectiveness of a drip irrigation system, it should be fully automated and connected to a series of sensors, the installation of these is discussed below.

There are several disadvantages and potential problems with a drip irrigation system. Costs of the product and its installation can be relatively high compared to more simple alternatives, although these may eventually be outweighed by savings in water bills. The systems are vulnerable to blockage by organic matter, either in the water supply or algal growth in the pipes themselves. Chemicals and filtering systems can be used to minimise these problems. These problems should be brought up when considering drip irrigation and discussed with the installation company to fully assess suitability of such a system

Sprinklers

Sprinklers can be used to set up a simple irrigation system, and would normally be used with a simple tap timer. Sprinklers can be moved manually to ensure an even distribution of water over the ground, but a series of small fixed sprinklers are what is more commonly used in an irrigation system. The "throw" of a sprinkler is the area of land which receives water from it and sprinklers are placed "head to head" meaning that they are placed sufficiently close together that there are not gaps of dry land between them. This can mean that the sprinklers must either be large in size or number and so may not be suitable for irrigating some areas.

The garden's function should be of primer consideration when deciding whether a sprinkler system is suitable. Pop up sprinklers are the best suited for lawns as they are out of sight most of the time. Most systems are fitted with internal filters to prevent them from being blocked by hard water. Before you purchase your sprinklers make sure this is the case.

Sprinkler systems must be completely drained before the winter to prevent damage, and some part may even need to be removed. A sprinkler system may last over fifteen years although they require regular servicing and replacement of parts.

Pumps

Small porous pipe dripper and microspray systems can be run simply from a tap. As the water is required to travel further however, the pressure required must be generated by a pump. Pumps of different sizes and strengths are available according to the type and size of the irrigation system. If the system is classed as a "permanently installed underground system" then bylaws state that it must be fed by a tank and pump. This requires for a tank to be purchased and installed which may complicate planning stages and increase price. You should consider this excess price with the total price in mind and if it seems particularly high, discuss alternative options with the installers.

Always ask the company who is selling and installing the pump to explain processes such as "pump cycling" which can often reduce the efficiency of an irrigation system but can easily be solved with small adjustments.

Timers and sensors

Electronic timers and sensors which adjust the watering cycle according to rainfall, sunlight and soil saturation can be installed. This reduces water loss while ensuring plants receive water at the right time. The most simple system is a battery operated timer that will simply turn a tap supply on or off which supplies water to the whole area. More complex computer driven systems may take information from across the system and adjust water pressure and output according to the requirements of each zone. Before purchasing such a system make sure that you will be able to fully operate the computers, as even the most self-sufficient systems need fine tuning.