Properly Planning a Backflow Preventer Installation on an Existing System

Performing a backflow preventer installation on an existing fire suppression system can be an intimidating job — the installer’s level of experience and background within the trades can be the difference between a successful, profitable installation and a frustrating experience. At Test Gauge, Inc., we have seen the good and the bad. With a combined 60-plus years of experience as a wholesaler specializing in backflow prevention, and a combined 40 years of field level experience as plumbers, we have assisted customers with many different levels of new or existing large backflow installations. From the basic installation — which we would consider a direct changeout where none of the system piping needs to be altered — to a more advanced retrofit where re-piping is needed to accommodate the installation of a required backflow preventer.

We mentioned profitability in the previous paragraph, as this is obviously a critical factor for the installing contractor. Another equally important component of the retrofit installation is making sure that the installation meets local plumbing and fire codes. Of course, this can add additional costs that need to be figured into the proposal for a retrofit installation. Additional costs may include job-site meetings, hydraulic calculations, permit fees, and final inspections. Depending on the Authority Having Jurisdiction (AHJ) / municipality where the installation will be taking place, there could be a significant amount of administrative work that needs to occur before the actual installation can proceed.

A real-life example of this work was recently completed by a Chicagoland area plumbing contractor at an existing building in Arlington Heights, Ill. The Village had performed a survey and found that this location did not have a properly installed backflow preventer on the incoming water service for the fire sprinkler system. There also wasn’t an approved backflow assembly on the incoming water supply for the building’s domestic water, which is required per the State of Illinois Plumbing Code. Our customer was tasked with bringing this location into compliance with both local and state plumbing and fire codes.

To begin, the plumbing contractor performed a survey at the location to get pictures of the existing piping and measurements. In the “before” picture (next page), there were four main elements that needed to be looked at:

1. This municipality requires a fire line meter. This is a combination meter for both the fire service and domestic water service. Part of this project was to remove the existing six-inch fire line meter and install an updated version.
2. This is the point of connection (POC) for the two-inch domestic water service. This service will need to have an approved backflow preventer installed on it.
3. The existing (unapproved) six-inch single check valve that was installed for the fire sprinkler service will need to be removed, and an approved, testable backflow preventer needs to be installed at this connection point.
4. The six-inch incoming water service from the street will need to be re-worked. The municipality requires a bypass for the six-inch fire line meter for routine maintenance, which allows them to service the main six-inch meter without interrupting the domestic water for the building.

For this survey, the installing contractor also requested that a representative from the Village of Arlington Heights’ Water Department be present, along with the plumbing inspector and fire inspector. They also requested that Test Gauge, Inc. be on-site, as we were helping facilitate the design and supplying all materials needed to complete the installation in one complete package. This meeting allowed the different departments involved to work together to ensure all codes and requirements were being followed, as set by the local municipality. In our experience, having all entities work together produces a more efficient and all-around better installation. This also leads to a better product for the building owner with less surprises, which usually equal additional costs.

Once the survey was finished and all requirements for this particular municipality were established, the material and labor take-offs were able to be completed. For a retrofit installation such as this, the exact backflow preventer, flanged fittings, valves, pipe, and accessories can be allocated to allow for a precise material list. Selecting the correct backflow preventer should always be the starting point. There are many different manufacturers, and all of them have different measurements. There are also different configurations that can be used. This municipality requires a reduced pressure (RPZ) backflow preventer on all fire sprinklers systems located in their jurisdiction. Because the existing single check valve had such a small take out, finding a standard RPZ to replace it with was not possible. Also, the existing horizontal piping was only 12 inches from center to the finished floor. Installing a standard RPZ could not be done because the installing contractor would not have the required 12-inch clearance from the bottom of relief valve to the finished floor. The best fit for this space ended up being a six-inch Wilkins 475ST, configured as an N-pattern. Butterfly control valves were selected for this backflow preventer (there is not a fire pump on this system, so they are allowed) to keep the installation compact. The N-pattern design allowed for the least amount of re-piping and made for the most efficient installation from a material and labor standpoint. Once the backflow preventer was selected, the rest of the material take-offs could be completed and labor could be calculated to provide an accurate proposal. After the proposal was approved by the building owner, the proper permits had to be applied for through the local municipality. In our experience, the permit review process can take anywhere from one to four weeks, depending on the municipality. After the permits were approved, the specified backflow preventer and all other installation materials were ordered.

NOTE: At Test Gauge, Inc., we always recommend applying for a permit or contacting the local municipality to ensure the correct backflow preventer is being installed. We have heard of contractors installing a new backflow preventer without a permit only to find out it’s not what the municipality or AHJ requires. It then needs to be replaced with the proper style of backflow preventer, at the cost of either the installing contractor or the building owner.

With the administrative portion of the process complete, the contractor had to schedule water shut-off and coordinate with both the water department and the building owner to find a time that would have the least amount of impact on the building’s operations. During an installation that requires an entire building’s water to be shut off for an extended period of time, it is advised to plan well in advance for the shutdown.

In the “after” picture, we can see what the final product looks like. Here is the breakdown of the completed scope of work:

1. The contractor removed the existing six-inch fire line meter and replaced it with an upgraded fire line meter. Included were two new six-inch OSY control valves — one on the inlet side and one on the outlet side for isolation.
2. A new two-inch RPZ, with proper strainer and air gap, were added to the main domestic water supply for the building.
3. The new six-inch RPZ (as required by this municipality) was installed at the connection point to the fire sprinkler system.
4. The required two-inch domestic water bypass was installed around the six-inch fire line meter for future servicing.

The complete installation was done, from start to finish, in one day. Proper planning and preparation from the plumbing contractor made this job a success!