HETEK Solutions Inc

Hydrostatic Test Failure

No excavation is required for the Tracer Gas testing, since the same feed and blow-off points as the original hydrostatic test can generally be used. In many cases, the HETEK Tracer Gas Injection Method becomes the only alternative as a cost effective approach and solution to locate leaks from a hydrostatic test failure.   The Waterworks Industry has continued the ongoing work of rehabilitation and growth of their water distribution systems by installing new water mains, replacement, or pipe relining of existing water mains. In the past, most new installations were composed of ductile iron main with copper services.

However, over the past several years, many Municipalities favor installing PVC (plastic) mains and services.   Before being accepted by the municipality, new installations must pass AWWA standards. This generally involves a Hydrostatic test in order to determine that the water main, valves and fittings have been installed properly, and will not leak under normal or adverse conditions. If the water main does not pass the test, the contractor must find and repair any leaks on the system until the water-conditioning test is passed.   Until recently, there were three basic methods of finding leakage on water mains that failed the hydrostatic test. The first technique is a visual examination of the ground surface for wet spots or surfacing water. The next procedure is usually excavating and exposing every joint and fitting. The last procedure is leak detection by electro-acoustic listening. The first two methods are self-explanatory.

The third option makes use of traditional leak detection methods using standard listening equipment, based on the theory that a fluid leaking from a conduit generates a sound and therefore can be detected acoustically. All acoustic equipment, from the most primitive (listening on a valve with ones ear on the key) to the most sophisticated (the leak noise correlator) depends on this theory. However, the small leaks that normally occur due to hydrostatic test failures, particularly on a PVC installation, sometimes do not generate sufficient leak noise, which therefore cannot be detected using traditional means.   HETEK Solutions Inc. has developed a different, and more "cost" effective method for detecting these small leaks, called the Tracer Gas Injection Method.  

Using the same feed and blow-off as was used in the hydrostatic test, the main is de-watered, and a mixture of 10% Helium to 90% Air is injected into the water main. The pressure is elevated to the point where a pressure drop is noted, indicating that a mixture is escaping from the leak and entering the ground. This tracer gas will eventually appear in one or more 12 mm diameter test holes placed at predetermined intervals along the water main, and can be detected and pinpointed using a Helium Detector.