Backflow Information

Cross Connection Control Program/Backflow Prevention

Important Forms: 

MPW Backflow Assembly Test Report

MPW Annual Testing Agreement


MPW Cross Connection Control Manual

South Carolina DHEC Cross Connection and Backflow Prevention Webpage (Includes listing of certified testers)


Attention Irrigation Customers!

On June 13, 2000, the S.C. Dept. of Health and Environmental Control required all new residential irrigation meters be protected with a backflow prevention assembly. The MPW Commission amended the Backflow Prevention Guidelines to also include meters installed before this date. If you have an irrigation system that is tied to the public water supply, your irrigation meter must have a backflow preventor to protect the MPW water system from potential contamination.*

* Under certain conditions, pesticides, herbicides, and other contaminates may enter your irrigation system, which if not properly isolated by a backflow assembly, could then enter the public water supply.

Installation Requirements

Testing Requirements


ACTION STEPS to help get you started:



How could the water in the customers’ plumbing system flow back into the public water supply?

MPW may have to shut off a water main in isolated areas to make repairs. This may cause a drop in water pressure, allowing water inside a customer’s plumbing to flow back into the public water system due to gravity. Sometimes customers will have pumps downstream from the water meter which could inadvertently pump water back into the public water system. These are just two examples of “backflow”.

How can backflow be prevented?

Backflow can be prevented by installing a backflow preventer. This a device that is installed on a water service that will only allow water to travel in one direction—from the public water supply to the customer.

MPW's Backflow/Cross-Connection Control Program

Mount Pleasant Waterworks initiated a Cross-Connection Control Program In accordance with regulations from the South Carolina Department of Health and Environmental Control (SCDHEC). The program was initiated to safeguard public drinking water supply by preventing the water in a customer’s plumbing system from flowing back into the public water supply. The Commission requires all irrigation systems be fitted with a reduced pressure (RP) backflow prevention device (see diagram below). In addition:

What to look for —and how to fix— potential areas around your home that could be the source of cross-connections:

POTENTIAL PROBLEM: water hose that is attached to fertilizer, pesticide or herbicide sprayers could contaminate your water supply You can reduce the risk of contamination through this type of cross-connection by shutting off the water supply to the hose at the faucet when you are finished. Even if the hose has a valve on the nozzle attachment, any decrease in water pressure could siphon the water from the hose — or the sprayer — back into your plumbing system.

FIX: Purchase a hose bib vacuum breaker, available from any hardware store, that will prevent back-siphonage.

POTENTIAL PROBLEM: A hose left in a bucket used for cleaning.

FIX: Remove the hose from the bucket (or sink) and shut off the water at the tap.

POTENTIAL PROBLEM: Underground irrigation systems are one of the types of cross connections posing a health hazard to the public drinking water system. Contamination from herbicides, pesticides and animal droppings can enter your irrigation system when below ground sprinkler heads are used.

FIX: Installation of a reduced pressure (RP) backflow prevention device (example below). (Note: The Commission requires all irrigation systems be fitted with an RP device to prevent contaminated water from flowing back into the public water supply.)