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Cross-Connection Control: Protect Your Drinking Water 

Proteja su agua potable

We’re providing this information as part of our residential cross-connection property survey required by the City of Milwaukee and the Wisconsin Department of Natural Resources. The purpose of the Cross-Connection program is to ensure certain water-related fixtures are placed properly to protect the safety of the city water supply.

We look for potential cross-connections in residential properties when we exchange a water meter.

What is a Cross-Connection?

A cross-connection is an actual or potential connection between the safe drinking water (potable) supply and a source of contamination or pollution. State plumbing codes require approved backflow prevention methods to be installed at every point of potable water connection and use. Cross-Connections must be properly protected or eliminated.

How does contamination occur?

When you turn on your faucet, you expect the water to be as safe as when it left the treatment plant. However, certain hydraulic conditions left unprotected within your plumbing system may allow hazardous substances to contaminate your own drinking water or even the city water supply. Water normally flows in one direction. However, under certain conditions, water can actually flow backwards; this is known as backflow, when pressure drops in the city water system.Do not leave a hose with the open end in a container, like a bucket of water for car washing.

There are two situations that can cause backflow: backsiphonage and back pressure.


May occur due to a loss of pressure in the city water system when:

  • fire fighters quickly open a hydrant to pump water for firefighting
  • a sudden and massive water main break occurs
  • there is a power outage to a pump
  • system repairs are being made

These create a siphon in your plumbing system which can draw water out of a sink or bucket and back into your water or the city water system.


May be created when a source of pressure (such as a boiler) creates a pressure greater than the pressure supplied from the city water system. This may cause contaminated water to be pushed into your plumbing system through an unprotected cross-connection.

Examples of cross connections that may allow contaminated water to mix with clean drinking water:

  • A hose connected to the laundry tub faucet is submerged in a sink filled with soapy water.
  • A toilet fill valve (ballcock) is submerged below the water overflow line.
  • A non-plumbing-approved fill valve was installed in a toilet.
  • A handheld shower hose that does not have a back flow preventer.

A hose bibb is a faucet with screw threads on the end. This can be found on the exterior of a building and in the laundry tub. The screw thread can be used for attaching a hose.

Tips to prevent backflows

  • Keep the ends of hoses clear of all possible contaminants.
  • Install a simple hose bibb backflow prevention device on all threaded faucets in and outside your home.
  • Make sure dishwashers are installed with a proper "air gap" device.
  • Make sure water treatment devices such as water softeners have the proper "air gap," which is a minimum of one inch above any drain.
  • Do not use spray attachments without hose bibb backflow prevention devices.
  • Do not connect waste pipes from water softeners or other treatment systems directly to the sewer or submerged drain pipe. Be sure there is a one-inch "air gap" separation.

Garden hoses connected to outside faucets can create a potential cross-connection. Here are tips to avoid problems:

  • Install a hose bibb backflow prevention device on your exterior faucet, or hose bibb, before attaching a garden hose.
  • Do not leave a hose with the open end in a container, like a bucket of water for car washing.
  • Do not leave a hose submerged in buckets, pools, tubs, sinks, swimming pool or pond.
  • After using a sprayer attached to a hose for weed killing, etc., remove the sprayer for storage.
  • Do not leave a hose lying on the ground or lawn, which may be contaminated with fertilizer and garden chemicals. Hang up the hose on a rack.

This exterior faucet, or hose bibb, has a hose bibb vacuum breaker attached to it to prevent backflow. Make sure to drain exterior hose bibb vacuum breakers before freezing winter temperatures set in.This exterior faucet, or hose bibb, has a hose bibb backflow prevention device attached to it to prevent backflow. Make sure to drain exterior hose bibb vacuum backflow prevention device before freezing winter temperatures set in.

When your residence is checked for cross-connections, our meter technician will check for potential cross-connections. If your laundry tub faucet has exterior screw threads for use with a hose, we will give you a hose bibb backflow prevention device you can attach to the faucet. For liability reasons, the water meter technician is not allowed to attach it for you. We will give you a second device to attach to the garden hose faucet outside your home if it also has exterior screw threads.

Questions? Please call Milwaukee Water Works – Meter Services at (414) 286-8000, Monday – Friday, 8:00 am to 4:30 pm or visit milwaukee.gov/water/WaterQuality/Cross-Connection-Control.



Customer Service Center
For billing and related questions: 


24-Hour Control Center
For water emergencies only:


  414-286-5452 (Fax)

Email: [email protected] 

 Zeidler Municipal Building, 841 N. Broadway, Room 406, Milwaukee, WI 53202

 Monday - Friday, 7:30 AM - 4:45 PM

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