There are quite a number of considerations before you begin to plan the installation of a new lawn irrigation system. In some areas, you may need to make sure that the soil in your planned landscaping is, in fact, irrigable and that you do have a readily available water source.
Also, checking with your local laws and ordinances about water usage can also solve many problems before they even arise, so this is always a good common practice to ensure that you are in adherence with those. The next aspect involves more practical application- you need to measure your yard and be sure that you are accurate.
One of the more common issues that comes up with home irrigation systems is in bad measurements resulting in either dry spots or too many sprinklers per square foot. Be sure to include buildings in the area, their perimeters and use the straight lines of those to measure the exact space and perimeter that needs irrigation. Be sure that you are taking into account any other buildings, trees, or structures in the area, as well.
Next, you will want to be exactly sure of your water meter size. If you are using city water or water from a company this is a consideration that you have to also note. Some companies do not use a water meter and may instead go with a flat rate, however, if you do in fact have one, read on. You'll need to not only find your meter's size, but you will need to be able to calculate the amount of pressure loss as well. This is usually determined by both the meter's size and its flow rate.
Backflow preventers are another thing- most areas, these are the law. If they aren't, though, and you do not install a backflow preventer, you will find yourself with some major problems with your irrigation system, namely due to the nature of irrigational flow. The water used in your yard's irrigation goes through all sorts of things in the soil- these things, when in your own water supply could make you very ill. Imagine, every dog or cat that visits your yard, and what they do- without a backflow preventer, this, and more, can come back into your water supply without a backflow converter.
The reason that backflow converters and certain types are usually required by some places by law is, many communities share water and not only can an irrigation system that doesn't have a backflow converter contaminate your water, but your neighbors' as well. Of course most of the time, water pressure prevents this, but any time your water pressure drops, say, if you turn it off to repair plumbing, a backflow is a definite possibility.
These are just a few of the potential pitfalls that you might encounter without properly preparing your property for irrigation do it yourself. Usually, a qualified professional is already aware of most of these things and can easily circumvent them.