Water distribution systems are vulnerable because air valve outlets can allow contamination into a potable water system.  There is a system that prevents contaminated water from entering a portable water pipeline or reservoir through an air valve or reservoir vent.


How does it work?

Before the issue of cross connection and security, valve vaults were just a part of the water distribution system that needed little attention.  Then there was the arrival of cross connection issues and concern increased for the potential for non-potable water entering a pipeline through vault installed air valves.

The valve outlets were often not piped leaving them exposed to floodwater or other contaminates.

Water businesses insisted that all air valve outlets be piped above grade using a “J” pipe configuration.  This was extremely impractical as vaults below streets were opened up to a higher possibility of malicious tampering of the “J” pipe.  In cold climates the air valve outlet was now also exposed to extreme temperatures making freezing an issue.


Important parts of valve vaults;

Air valves – play a critical role in the operation of distribution systems as they provide efficiency by preventing air pockets from developing at system highpoints, reducing capacity and increasing pressure loss.

Air/vacuum valves– help the system release large volumes of air during system start up and admit air when necessary to prevent a vacuum from forming and creating a pressure surge.

Reservoir vents – important in the intake and exhaust of air from reservoirs as the water level inside rises and falls


Attempts to increase the security of “J” pipe configurations have been made.  One method being used is to have screens mounted at the end of the pipe as well as in the pipe itself. However, “J” pipes still don’t solve the problem of floodwater or intentional introduction of a contaminate finding its way to the outlet of an air valve or reservoir vent

Many new approaches have been brought about in recent years concerning cross contamination and the protection of our drinking water. One of these is the concept of inflow prevention. Inflow prevention is defined as preventing contaminated water from entering a potable water pipeline or reservoir through an air valve or reservoir vent.  It is similar to backflow prevention as it impedes contaminated water from compromising drinking water.  Most backflow has an inline device that reacts to pipeline pressure changes.  Inflow prevention is a way to stop contaminated water from reaching an air valve or vent outlet while allowing the valve or vent to perform its function.

Inflow Preventers

An inflow preventer is a device that stops contaminated water or other fluids being allowed into a potable water pipeline or reservoir. Inflow preventers are installed on the outlets of air valves and reservoir vents.

As well as keeping contaminated water away from drinking water, backflow and inflow preventers both have two other concepts:

-the need for inspection and testing in the field to assure that the device is functioning properly

-the need for redundancy

Product standards will more often than not include provisions for both annual inspection and field-testing.  By following the successful and proven path of the backflow community and including field inspection, field testing and operation redundancy, inflow prevention is proving to be as essential as backflow prevention.

Why Inflow Prevention is so important:

Air valves and reservoir vents are vulnerable to cross contamination and tampering so inflow prevention is extremely important.

There are two types of air valve vault installations, un-piped and piped above grade with a “J” pipe.

Left un-piped, an air valve outlet is exposed to the atmosphere. If the vault floods and the air valve opens, contaminated flood-water will be drawn into the system. If piped above the grade, the same will happen if the floodwater reaches the elevation of the top of the “J” pipe.

Worse results can happen through tampering. It is a simple matter to cut off the top of a “J” pipe or drill a hole into it with a potable drill. Once done, a corrosive liquid can be poured down the “J” pipe, destroying the valve and leading to flowing and contamination. Inflow preventers can substantially reduce all of these threats

For solutions in water distribution system applications involving inflow prevention Valmatic can provide the correct air valves.  MGA are a UK based company and are the exclusive suppliers of Valmatic products across Europe.