Sprinkler Season is Upon Us!

HOW TO LAY OUT A HOME SPRINKLER SYSTEM

                

Possibly the most difficult step in implementing a home sprinkler system is settling on a layout to use. Several variables have to be taken into account, such as the water pressure on the property, the overall shape of the lawn and designating the layout of watering zones on the property. This article should provide some general guidelines that can help make designing the layout less of an ordeal.

GAUGING WATER PRESSURE AND CAPACITY

The first step in the design of an irrigation system needs to be checking the main water supply’s output and pressure. The key elements of the irrigation design will depend on the water capacity and pressure of the supply line. If the water is coming through at over 30 psi, rotor sprinkler systems become an option. Less than 30 pounds of pressure means that a pop-up spray system will be ideal, as misting – where water is being forced through the spray heads at too high a pressure – becomes an issue at pressures exceeding 30 psi.

For measuring the flow of water, a simple mathematical equation should provide the answer. Take a 5 gallon bucket and time how long it takes for the bucket to fill from the water line. Divide 60 by the number of seconds it took, and then multiply that number by 5 – the number of gallons – to get the gallons per minute. As an example: filling the 5 gallon bucket takes 15 seconds. 60 divided by 15 is 4. 4 multiplied by 5 equals 20, so the flow of the main line is 20 gallons per minute.

MAPPING THE YARD

The next step in the designing process is drawing a map of the area that will be watered. It is important to note the different things in the yard such as trees or shrubs, where the yard meets the sidewalk, flower beds or other features of the lawn. It is also important to note the location of the main water supply line on the map.

When designing the layout for the system it is a good idea to factor in the sprinkler head ranges you will need to cover all sections of the lawn. The sprinklers should be spaced so that the radius of one head reaches the next sprinkler in the zone. This is called “head-to-head spacing” and is used to make an efficient watering grid for the sprinkler system. Using head-to-head spacing prevents watering gaps in the yard, which would lead to patches of grass that would not be fully watered – if watered at all. After mapping the sprinkler heads for the system, be sure to note how many heads were drawn on the plan and which spray arcs they were, so the proper parts can be purchased later on.

Designing zones may end up being one of the more complicated steps in designing a home sprinkler system. It is important to keep areas such as gardens and flowerbeds separate from the main lawn area when forming groups for zones, as they often require their own specially tailored series of sprinkler heads.

When designating the watering zones, it is important to take into account the amount of water each zone will be using. As a rule of thumb, zones using 3/4-inch supply pipe for the yard should not exceed 13 gpm and zones using 1-inch supply pipe should not exceed 18 gpm. This will require knowledge of the flow capacities of the sprinkler heads being used, so it is a good idea to consult manufacturer information for the sprinklers you will be using.

SELECTING CONTROL VALVES

Once the zones have been mapped out, the control valves need to be selected. Each zone will be controlled by an individual valve that opens and closes for the specific zone based on instructions from the controller or timer. The specific valves used will be determined by the water pressure and flow of the supply line as well as specific plumbing regulations for the city. Most cities will require that a valve be installed with a back-flow prevention device that is either installed before the valve manifold or is built in to the valve itself. The most commonly used valves and back-flow preventer for a residential system are a diaphragm valve paired with a pressure or atmospheric vacuum breaker.

It is also necessary to map out the location of the valves. In the case of residential systems, it is increasingly common for homeowners or contractors to group the valves together in a manifold that is close to the main supply line. The grouped valves are usually covered by what is known as a valve box, a protective plastic shield that keeps valves out of sight and prevents dirt from entering and damaging the valves.

MAPPING THE PIPES

After mapping out the sprinkler heads and control valves, mapping out the pipes is the next step. This is done on a zone by zone basis. Starting from the sprinkler head in the zone that is furthest from the valves, draw a line that leads back to the valve for the zone. In many cases, it will not be feasible to connect all the sprinkler heads through a single line of pipe. In zones where the sprinkler heads are arranged in a grid, for example, it is more efficient to set up a main line that branches off into smaller lines that provide an even water distribution and preventing loss of pressure. The placement of the main line for the valve is important as well. If the branches are too long, sprinklers at the end of the branch are going to be watering inefficiently due to the pressure loss. In zones that consist of a single line of sprinkler heads, such as with a line of shrubs, only one line of pipe is required.

Be sure to note the measurements for the lengths of pipe that have been mapped out, as well as noting the number and types of fittings (the points where pipes intersect or where heads will be installed) in the design. It is important to take into account the type of pipe that will be used for the system. Schedule 40 PVC or Polyethylene pipe are the most common choices for piping in a home sprinkler system.

By far, the most often used pipe in a sprinkler system is PVC. Polyvinyl chloride piping is inexpensive, very durable and very easy to assemble. PVC piping comes at differently rated strength levels, and some local codes may require a certain strength rating on pipe used for home irrigation and sprinkler systems. The strength of the PVC pipe will determine the pressure of the sprinkler system it can be installed in.

Polyethylene tubing is black, flexible pipe that is used primarily in areas with cold weather. It is becoming increasingly common as an alternative to PVC. PE pipe is more resistant to freezing than PVC pipe is and can be used in low-pressure systems. PE piping has a generally lower pressure threshold than PVC and is not suited for high-pressure water systems, however as most residential systems do not reach 100 psi, it is a completely viable alternative.

COLD-WEATHER DESIGN CONSIDERATION

In areas of cold climate, it will be required to winterize the system each year when the temperature drops in order to prevent damage to the system. This will require consideration of winterizing options such as drain valves or using a compression pump. If planning to use manual valves, be sure to mark the locations on the grid. They will need to be installed at all low points in the system as well as the ends of each zone branch. With automatic valves, they should be placed at 50-foot intervals and at every low point as well. If planning to use an air compressor for the system, it is generally a good idea to plan for an adapter right before the valves in the valve manifold that an air compressor can be attached to.

PURCHASING THE PARTS

Once you have a list of all the parts that will be needed, you can go to www.PlumbersStock.com with the parts list and purchase or order the parts you will need. Once the parts arrive, the installation process can begin.