When it comes to irrigation systems, you want to make sure you are placing your components in the right location. The main things to consider are your backflow preventer, valve box and valves, main line and lateral line placement.
Backflow Preventer
When you're designing your irrigation system, you want to plan where you are installing your backflow preventer. You will want to place it after your water meter, at your point of connection, after your shut-off valve. All in-ground irrigation systems must have some sort of backflow prevention device. You will want to install it in an area where you can easily access it for servicing and testing. Your backflow prevention device should be tested, once installed, by a certified backflow technician.
You must use a backflow prevention assembly device in any kind of potential backflow or back siphonage situation. Backflow prevention devices should be installed on all possible cross-connections to any potable water supply. A potable water supply can be a city water supply, a well, or any other kind of drinking water supplied by your local water purveyor.
These are two examples of recommended backflow prevention devices:
DCVA (Double Check Valve Assembly)
This form of backflow prevention are most commonly used in irrigation. DCVA’s are for use in low to moderate hazard situations in non-health hazard cross-connections and constant pressure applications that can be subject to backpressure or back siphonage situations. There are two single check valves in the body of the backflow device. These are a testable form of backflow prevention with four test cocks and two shut-off valves. All DCVA’s installed in residential irrigation will need to be tested tri-annually according to your local water purveyors. Consult your municipality code to see what their testing requirements are.
Common uses for a DCVA
DCVAs can be either premise or in premise isolation, such as an irrigation system, which is considered to be a low to moderate risk, in non-health hazard application. However if using herbicides, pesticides, fertilizers and animal feces may collect in pools of water around the sprinkler heads creating a potential for contaminants to be drawn back through the sprinkler irrigation system making it become a moderate hazard.
RPBA (Reduced Pressure Backflow Assembly)
RPBAs are similar to a DCVA as it has two check valves these check valves are independently acting spring-loaded check valves separated by a spring-loaded differential pressure relief valve, two seated shutoff valves and four test cocks. Where they differ is the discharge port at the bottom of an RPBA and the applications that they are used for. If there was ever a leak in one of the check valves, or a backflow or back siphonage situation, the relief valve is designed to open and discharge the water out of the relief port. These are usually used in high-health hazard applications. An RPBA should be provided with proper drainage as it will periodically discharge small amounts of water due to the fluctuation of in-line pressure up or downstream of the backflow preventer.
Common uses for an RPBA
Are usually in high-health hazard applications, like a hospital, fire sprinkler systems, and household plumbing, although RPBA's can be used in irrigation as well. When using fertigation which is when the fertilizer is pumped into the line or when herbicides, pesticides, and fertilizers are used regularly it is recommended to use a RPBA. The RPBA is designed to prevent backflow caused either by back pressure or back siphonage and may be installed on either low or high-hazard connections.
Valve Box and Valves
For placing your valve box and valves you will want to choose an accessible spot away from heavy foot traffic and as close as possible to your main line. Your valve box can be located where it can easily be camouflaged into your landscape, yet easily accessed for maintenance. Your valve box will need to be properly installed with drainage gravel, landscape fabric and bricks to support the box to prevent the settling of the box and potential downward pressure on the pipe resulting in cracks and breaks. In a residential application, your valve size will generally be a 1-inch valve. In a regular 14" x 19" valve box you should generally be able to fit 3 valves in your box. We would not recommend any more than 3 per 14" x 19" size of valve box. You never want to stack valves on top of each other. Doing that will in turn make it impossible to do any future maintenance on the valves.
Main Line
Main lines can be anywhere on a property, typically at the edges of walkways, and the perimeter of the property, and or around house foundations. Your main line will be under constant pressure, so you will need a heavier-grade, thicker walled pipe for it compared to your lateral lines. The main line pipe should be either a municipal poly pipe or a Schedule 40 PVC pipe. You will want to make sure your main line is buried at a depth of 10-12 inches.
Lateral Lines
Lateral lines are any pipes that are after your valves running to your sprinkler heads or drip irrigation. These lines should be 8-10 Inches below finished grade. You will want to check your friction loss chart to see what pipe will work best with your pressure, flow and distance, just like you would for sizing your main line. The placement of your lateral lines will vary depending on what your watering, size of area, and or garden vs. lawn. When installing sprinklers it is best to install your lateral lines in an "H" pattern if possible, to better help your chances for an even flow rate and pressure to each sprinkler head. The lateral line is not under constant pressure thus giving you greater options for which kind of pipe you can use.
These are the top three most commonly used types of pipe.
Poly Pipe is commonly used in many irrigation applications as they are corrosion resistant, UV resistant, can withstand freeze and thaw cycles, and have a long service life. Poly prime comes in a roll, making it easy for transport and going around corners without breaking or kinking. Poly can range from many different sizes depending on the size you are looking for, for your installation.
PVC is one of the most common kinds of pipe used in irrigation. PVC pipe usually comes in 20 foot lengths, and has different thicknesses. Most commonly used is schedule 40 and class 200. Schedule 40 has a thicker wall generally rated for higher pressures and used high-traffic areas. Class 200 and class 160 have a thinner walled PVC which is usually used for lateral lines. Although you can use both kinds of PVC for your lateral lines. PVC is usually used in larger scale jobs for commercial uses, as you get generally get it in larger sizes compared to most other kinds of pipe. Another reason for the immense popularity of PVC is that it is cost-effective and lays flat.
Blu-Lock is recommended for residential applications. Blu-Lock pipe comes in a coil or straight lengths and has flex. Blu-Lock has a patented design which is 100% solvent free which means that it does not need clamps or glue. It is UV safe, environmentally friendly, and recyclable. Blu-Lock is a high-density polyethylene, meaning it can withstand higher impacts than regular poly prime and does not crack like PVC pipe can. Blu-Lock fittings require a low insertion force which makes installation fast and easy. The fittings are 360 degree rotatable, are built to last, since they are made with UV-resistant ABS, stainless steel teeth, and EPDM seals that are designed and tested to ensure they are leak-free and tough. Blu-Lock fittings are for use on the outside of the pipe, allowing unimpeded flow for a 25% increase of flow versus traditional poly insert fittings. Blu-Lock fittings are only for use on non-constant pressure applications; they are only to be used on the downstream side of the valves and are not rated for mainline use. However, if it is needed in a constant pressure situation you can use insert fittings on Blu-Lock pipe. Unlike PVC pipe Blu-Lock can be installed wet or dry which can help speed up the installation of the project. In addition, you can pressurize your system as soon as the installation is complete as there are no cure times. It is easy to switch from PVC to Blu-Lock with one fitting.
