How to Install a Backflow Preventer

The backflow preventer is designed for use with irrigation systems and water pipes, and it prevents water from flowing back up the pipe. Most backflow preventers are mechanical devices which create a physical barrier to prevent water flowing back. If you wish to install your own backflow preventer, then you must make sure that your mechanism is compatible with the water source you will be using, and that you feel confident about being able to install this complicated piece of machinery yourself, without assistance. If you are fairly sure that you can replace the system, then you should follow these simple rules in order to press ahead with your installation.

Step 1 - Getting Ready

Before you begin installing a backflow preventer, the most important thing that you should do is check the building code in your area. If you have any doubt, the local building code office, or your water supplier, will be able to tell you how deep you need to install your pipe, the dimensions allowed for the backflow preventer box, and the limits of installation. You should always check what is allowed in your neighborhood before commencing, as low winter temperatures, for example, can affect how deep you need to dig the pipe.

Step 2 - Locating the Pipe

Once you are sure that your machine will not break the buildings code for your area, then you can proceed. Dig down by the water main which is connected below your curb. You will locate a 1 inch copper pipe, which can be split into smaller pipes at the meter box. Everything which is on your home's side of the meter belongs to you. Close by the meter will be a valve which is used to shut off the water during repairs in the home. There may also be a pressure reducing valve nearby. You may have to dig up three to five feet away from the meter before you are clear of all this. You will also find small dimples near to the valves, which are known as meter nipples.

Step 3 - Installing the Backflow Preventer

Once you have dug through to the pipes, you can use two different versions of the backflow preventer to stop water flowing backwards. The first is called the Threaded and Glued, and involves dropping a threaded T device into the pipe, and connecting it to the Pressure Valve adaptor. Occasionally, this version requires that there be extra length in the line, so a small section will have to be removed, so that a joint can be added to lengthen the line.

The other version involves a compression fitting, which relies upon a pressure washer to seal around the outside of the supply pipe. Cut a small piece of the line, and the install a compression fitting around the cut. They will tighten and prevent water from flowing backwards. Find a metal compression device with a rubber washer fitting, and make sure to tighten it properly, without cracking the pipe or damaging the compression valve.