Trades Advisory Council
Basic Backflow Installation Guidelines and Requirements
(Not Intended To Be All-Inclusive)Revised January 2006
- All devices must be state approved and must meet University of Southern California specifications.
- Double Check and Double Detector Check Valve Assemblies may be vertically installed.
- All materials used must meet MWS specifications including use of brass, copper or class 52 ductile iron pipe on new installations. Heating devices are recommended but not required.
- Reduce Pressure Backflow Prevention Devices installed in new locations must be equipped with a "Y" strainer.
- It is recommended but not required that all new and replacement devices be equipped with a "Y" strainer.
- A combination fire/domestic line does not require a Y strainer.
- The relief valve must be installed a minimum of twelve inches plus the diameter of the device above finish floor level. This height is not to exceed six feet from the ground.
- *The Reduced Pressure Backflow Prevention Device cannot be used as a number two shut off or isolation valve for meter testing.
- MWS prefers all backflow devices be placed outside as close as possible to the point of connection. Requests for variance to this policy are processed through the Permits Office.
- New commercial businesses considered to be low hazard may not be required to install a Reduced Pressure Backflow Prevention Device. This will be determined by a MWS inspector during a site visit or through the variance process.
- If ,during the annual inspection of an existing commercial business, it is determined the conditions are low hazard, the owner may either remove the existing device or must continue to maintain it in working condition.
- All commercial and irrigation water service connections will be surveyed yearly for hazard status as well as testing of all prevention devices.
- High hazard premises include, but are not limited to jails, laboratories, nursing homes, sanitariums, laundries , hotels/motels, restaurants, major office buildings (multi- story), apartment houses, condominiums, service stations, shopping centers, mobile home parks, swimming pools, parks, mortuaries, morgues, hospital and medical buildings, chemical plants, manufacturing/food/beverage plants, car wash, exterminating, airports and transportation facilities, greenhouses, baptisteries, commercial buildings with commercial ice machines.
- Buildings that are over two stories and/or have mixed usage can be considered through the variance process.
- Low hazard facility could include an accountant's one story office with bathrooms, alteration shop with bathrooms, or one story retail shop with employee bathrooms.
- To request an inspection or approval on a building application for use and occupancy call 862-4600, option 5.
- To request a variance call 862-7225, fax written request to 862-7257 or e-mail mary.jackson@nashville.gov.
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