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Harper International, Article_6287, Val-Matic Air Valves

Harper International explains Air Valves. “How to Prevent Cross-Contamination from Floodwater Inflow through Air Valves”

How safe is your water system when it comes to cross contamination through vault installed air valves and reservoir vents?

How a solution to inflow contamination is finally available.

The Problem with Air Valves

Air valves

Air release valves are commonly installed in below-grade vaults. They’re needed to protect water systems from pressure loss and reduced capacities that occur when entrained air gathers at system high points.

While air release valves solve a serious problem, they also create the risk that non-potable water can enter a pipeline through the air valve.

These photos show a flooded pit (left) and submerged air valve (right), a condition that permits inflow.

Inflow contamination can be hard to detect, causing water companies to shut down service to many customers until the water quality is assured by discovering and eliminating the source of cross contamination.

Inflow Contamination

Here’s what can happen: A harmful substance is introduced to the vault, such as maliciously placed bio-toxins or e coli bacteria from a dead animal that found its way into the vault through groundwater contamination. The foreign substance may remain harmless in the pit until the vault floods and floodwater carries the toxins into the water supply through the air valve.

Alternatively, air may be piped above grade from the vault using a “J” pipe, which is at risk of malicious tampering and freezing. A terrorist can introduce toxins into the water system simply by cutting the “J” pipe, then pouring toxins into the vault through the pipe. Again, the toxins enter the water system through the air valve when natural or malicious flooding occurs.

Heightened Risk

Since 9/11, water systems have been identified as potential terrorist targets. At this year’s AWWA Water Security Congress, one homeland security official noted that water infrastructure is a regular target in the war in Iraq, and that terrorists are paying close attention to the effects of those attacks.

Meanwhile, Hurricane Katrina and other flooding disasters have focused attention on inflow contamination from natural sources. This year the EPA published a white paper on cross-contamination and backflow contamination issues, setting the stage for more rigorous standards. Another EPA paper covers intrusion contaminents.

The water industry has long been aware of the hazard of inflow to air valves, but we lacked viable solutions. To simply eliminate air release valves would cripple water systems in other ways.

Inflow Prevention

After years of development, Val-Matic has introduced an inflow preventer that is both simple and ingenious. While preventing floodwater from entering the air valve, the device – called the FloodSafe® – still allows the air valve or vent to exhaust and admit air to the system.

Here’s how it works. The FloodSafe® is piped to the outlet of an air release valve. As water in the flooded vault rises, the float check in the lower chamber rises. This prevents contaminated water from continuing past the chamber.

A redundant upper chamber provides a backup in much the same way a backflow preventer works. If contaminated water continues past the seat of the lower chamber, the float check in the upper chamber rises, preventing fluid from reaching the air valve outlet. Under normal operating conditions, the FloodSafe® provides full venting capacity of the air valve or vent. (Enlarged image of drawing.)

To find out more, contact a Harper representative.
Harper Haines Fluid Control, Inc.
125 Old Gate Lane, Milford, CT 06460
Telephone: 203.693.3740 * Fax: 203.547.6092