How To Install A Double Check Backflow Preventer

Residential properties

Air gap

I step you can accept to protect our drinking water is to proceed the ends of hoses out of pools or other containers while yous are filling them. For example, if a hose is submerged in the pool, the chlorinated pool water may enter the drinking water organisation during a backflow status. When filling pools, continue the end of the hose out of the pool and have a gap betwixt the end of the hose and the surface of the water. This gap must be twice the diameter of the hose and never less than one inch.

Hose bib backflow protection

Atmospheric vacuum breaker on hose bib — A hose bib backflow preventer keeps water from flowing astern up the hose.

Some residents choose to install a backflow device on their hose bib. These are called vacuum breakers and they do not need to be tested. You can purchase them at most plumbing and hardware stores.

Irrigation organization

double check valve assembly installed in valve box at property line — Irrigation double check valve associates installed simply afterward the water meter on private property at the property line.

Your plumber or licensed backflow associates testing company volition likely know which type of associates to use. Backflow assemblies near commonly installed on residential irrigation systems are the double check valve associates (DCVA) and the pressure vacuum breaker assembly (PVBA). The DCVA may be installed in a vault beneath finished grade. The PVBA must be installed at least 12 inches above finished class.

Commercial backdrop

The location of the assembly, service size, and adventure level of the connexion determine which backflow assembly you should apply. If you have questions about which type of assembly you need, contact the Water Agency Water Quality Inspection staff at 503-823-7480. Below are some assemblies usually used in commercial applications. More information virtually the all the following assemblies can be institute on our backflow assembly installation requirements page.

Reduced pressure level backflow associates (RPBA)

RPBA installed 12 inches above finished floor — This is a reduced force per unit area backflow assembly installed inside a building at the water riser. The assembly is four inches from the water and 12 inches to a higher place the finished floor. There are no connections allowed upstream of this assembly.

The reduced pressure backflow assembly (RPBA) is designed to prevent backflow acquired by backpressure or backsiphonage and may be installed on either depression- or high-gamble connections. Backsiphonage is when h2o moves in the direction opposite its regular flow.

During normal operation, the pressure betwixt the two check valves, referred to every bit the zone of reduced pressure, is maintained at a lower pressure than the supply pressure. If either check valve should leak, the relief valve is designed to open and discharge water to the exterior.

RPBA installed outside of building in insulated enclosure — This is an outside reduced pressure level backflow associates installed merely later the h2o meter on individual property.

A properly functioning RPBA will periodically release small-scale amounts of water due to changes in line pressure up or downstream of the associates.  For this reason, this type of assembly should exist installed in areas that are not discipline to water damage and have proper drainage. When backflow happens, a properly operation RBPA may release some water. If the RPBA becomes clogged by debris or is not functioning properly and needs repair, it may discharge a large book of water.

Double check valve assembly (DCVA)

Double check valve assembly installed inside building — A domestic double check valve assembly installed vertically on a riser within a building just within from a water meter. The premises isolation riser is 12 inches from the foundation wall to centerline and 12 inches above the finished flooring.

The double bank check valve associates (DCVA) is normally used to protect against backflow hazards that do non pose a health chance. They may be used under continuous pressure and protect confronting both backsiphonage and backpressure conditions. They can be installed above or beneath ground, but no more than than 24 inches deep or five feet above the floor or form.

Double bank check detector assembly (DCDA)

double check detector assembly installed inside a building — Double check detector associates installation at firsthand inside wall of building. This is installed 12 inches to a higher place the finished flooring.

The double bank check detector associates (DCDA) protects the potable water supply line from possible contamination or pollution from:

fire sprinkler systems
backpressure from burn down line booster pumps
stagnant water that sits in burn down system pipage over extended periods of time
the addition of nonpotable (not prophylactic to drink) water through exterior fire district connections (FDCs)
the detection of leaks or unauthorized water use

The assembly consists of two spring-loaded check valves, a bypass assembly with a water meter and double cheque valve assembly, and ii resilient seated indicating shutoff valves.

double check detector assembly installed inside a vault — Double cheque detector assembly installation in vault for a two-inch dedicated fire service.

Reduced pressure level detector associates (RPDA)

Reduced pressure detector assembly inside a building — Basement installation of a reduced force per unit area detector associates in a high-rising building. Backflow assembly lowered to five feet to a higher place finished floor.

This assembly is intended to protect the drinkable h2o supply from:

fire sprinkler systems that comprise chemicals or other additives
auxiliary water sources that use storage tanks or supply high-rise buildings

This assembly uses a mainline reduced pressure backflow assembly equipped with two resilient seated indicating shutoff valves, a bypass system containing a smaller reduced pressure backflow assembly, and water meter. The RPDA must be installed at least 12 inches to a higher place finished grade or the 100-year flood plain, whichever is greater.

Vacuum billow assemblies

There are two types of vacuum breakers: the atmospheric vacuum breaker (AVB) and the pressure vacuum breaker associates (PVBA). The Water Bureau doesn't allow either the AVB or PVBA to be used for backflow protection.

The AVB is among the simplest and least expensive mechanical types of backflow prevention device that the end user tin purchase. The PVBA is an outgrowth of the AVB and evolved out of a demand to have an atmospheric vacuum billow that was testable and could be used under constant pressure.