Transmission and Distribution

City of McAllen » McAllen Public Utility (MPU) » Departments » Transmission and Distribution

About Transmission & Distribution

Transmission & Distribution, formerly known as Water Line Maintenance, is responsible for water line issues such as breaks or leaks, fire hydrant installation, maintenance, and repair, installing and repairing meters, and regulation of the City’s backflow prevention program. Transmission & Distribution has approximately 40 full-time employees, and someone is on call around-the-clock to ensure that we can always meet the citizens’ needs in a timely manner.

The backflow prevention program is particularly important because the Texas Commission on Environmental Quality, or TCEQ, has mandated that all cities in the state of Texas implement such a program to prevent backflow or cross-connection contamination.

Please contact us if you notice a strange taste or odor to your water, for meter leaks and repairs, or to report a water line break.

Call before you dig! If you are going to do any digging on or around your property, please call Texas One Call at 800-344-8377 to locate any water lines, natural gas lines, and buried electric/phone cables. One call could save your life.

Backflow Prevention Program

Please click here to read the McAllen Public Utility Backflow Prevention Policy (PDF document).

What is backflow?

Backflow is defined as the reversal of flow of water through a cross-connection into the public water system. Water tends to flow in the direction of least resistance, which is taken into account when we design a public potable water system. However, there are occasions when water pressure may unexpectedly decrease, in which case the water will flow backwards due to gravitational pull. Here is an example:

Jane is fertilizing her flower garden with a liquid fertilizer hose attachment device. She hears the fire truck screaming down the street, and turns her head to stare as they screech to a stop at the end of the block. Only then does she notice the smoke coming from her neighbors’ home. She drops the handheld attachment and sprints to her next-door neighbor’s house to see if he knows what’s going on down the street.

Jane’s next-door neighbor, Bob, finally answers the front door. He was on his back porch filling up his hot tub, which was a little low after some hot weather. He left the water hose submerged in the hot tub to go answer the frantic knocking at the door. After a little discussion, they decide to go see if Mrs. Brown needs any help. She is elderly and lives only two doors down from the house that’s on fire. They want to be sure that if it’s necessary to evacuate, she can get out.

Mrs. Brown was giving her little dog Pepper a bath. Pepper really likes to swim, so she’s filled the bathtub up halfway and Pepper is currently enjoying himself, splashing around in the soapy water. She was about to rinse Pepper off with a handheld showerhead when someone begins repeatedly ringing the doorbell. She looks at the soapy, wet little dog and decides he is fine by himself in the bathtub for just a minute while she sees what the fuss is all about. She leaves the showerhead dangling in the water.

The house at the end of the block is most definitely on fire, so the firefighters attach their hose to the neighborhood fire hydrant and open the valve all the way. All the water flowing throughout water mains in the area is temporarily diverted to the fire hydrant, creating a sudden and dramatic drop in water pressure. The fertilizer-infused water from Jane’s handheld fertilizer attachment is siphoned back up the water hose and into the treated water system. So is some of the hot tub water from Bob’s backyard. And little Pepper, happily swimming in his bathtub, is suddenly interrupted by a strange sucking noise coming from the showerhead, which is odd because he didn’t think it was alive until it started making noises at him. Soapy water from Pepper’s bath joins the water traveling backwards into the main water system.

What has happened is called backsiphonage. When there is a drop in water pressure, it can create a natural vacuum which will pull water back into the main system. While this is a heavily dramatized scenario, incidents like this can and do occur all the time. Think about the last time you were watering your garden. Did you leave the running hose setting on the soil while you went to do some other yard work, only to come back and find it submerged under a puddle of water? If there would have been a drop in pressure, soil bacteria and other organic materials in your garden could end up back in the treated water supply of your home.

The other type of backflow is known as backpressure. Backpressure can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. A brief example of this type of backflow: There is a natural gas-powered boiler home heating system in operation under approximately 15-20 lbs of pressure inside the boiler. A water main breaks downstream from where the boiler is located, and the supply line pressure drops below 15 psi. The water inside the boiler flows back into the supply feed tube because the pressure inside the boiler is higher than outside, causing the water to flow back up the supply pipe. Now, the contaminated boiler water, which was exposed to heated metal elements—that may have corrosive deposits on them—is deposited back into the municipal water supply.

What is the backflow prevention program and why do we need it?

It’s our job to make sure the water entering your home is safe. Backflow can introduce all manner of unwanted materials into the treated water supply. Federal and state laws require public water suppliers to create regulations to prevent contamination in the water system. We are not only protecting our citizens from exposure to chemicals and other inorganic matter that could be toxic, but also from disease. For example, if an improperly sanitized swimming pool were to backflow into the system, a large amount of diseased water would enter the potable water supply and could be transmitted to several homes, where the water may be used for drinking or cooking, passing on the disease. This is why we require backflow prevention devices on all swimming pools. To read some case histories of actual backflow occurrences and the resulting problems and expenses, click here.

You may visit the TCEQ Web site to view a brochure about consumer backflow prevention.

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What is a cross-connection?

A cross-connection is any physical connection to the potable water supply and a liquid or a gas line through which contaminants can enter the treated flow and potentially cause harm. Examples around the house include garden hoses, washing machines, dishwashers, hot water heaters, automatic irrigation systems, swimming pools, and any handheld nozzles that do not have a shutoff valve and may be immersed in water (like a detachable showerhead that is attached to a hose). An example of a gas line cross-connection would be an air compressor attached to dental equipment at a dental clinic, or a carbonation cylinder attached to a soda fountain. Air in the lines not only causes sputtering and inconsistent flow at faucets, but air also can contain airborne illnesses that may be able to live in water and infect others.

What are the types of backflow prevention devices, and where in my home do I need them?

The City of McAllen has approved two types of backflow prevention devices for use: the reduced pressure device (RP), and the pressure vacuum breaker (PVB). Depending on the health risk associated withcertain cross-connection, one of these must be installed. The City requires the pressure vacuum breaker to be installed on all irrigation systems, and the reduced pressure device to be installed on all swimming pools. We also require businesses to install backflow prevention devices on lines connected to such machines as soda fountains, fire sprinkler systems, industrial boilers, and the like. Examples of businesses that are required to have backflow prevention devices range from restaurants and drycleanersto hospitals, mortuaries, factories, andsewage systems.

Why does the device have to be tested annually, and how do I know who’s certified?

TCEQ has mandated that all backflow prevention devices be tested at least annually by a licensed tester to ensure that they are working properly. A maintenance report must be filed with MPU by the tester to prove that this has been done.Please click here to view a current list of backflow prevention assembly testers certified by TCEQ.

Please click here to download a copy of the tester's report that must be filed with MPU annually by the licensed BPAT tester.

Important Disclaimer: you do not have to use any of the testers on this list. MPU has provided this list for your convenience only. The City does not endorse or require any of these persons to be the one who tests your backflow prevention device. It is always your responsibility to ensure that the person you select is certified by the TCEQ to test backflow prevention devices. You may go to TCEQ’s Web site to verify a person’s eligibility if you are uncertain they are certified by TCEQ. If you are a certified tester and you wish to be added to the City’s listing, please contact us at 956-681-1660.