Here are real world leaktest results. If there was any doubt that water leak testing is needed, the actual results affirm the need. Keep in mind that many of these systems were light tested prior to the water leak testing. Imagine the long term damages and fire safety issues if these had not been water leak tested.
It is our position that water testing as described in 5.2.1.2 of ASHRAE 154-2016, should be the only acceptable method. If the requirement is for the duct to be liquid-tight, then the system should be tested with a liquid.
Enviroleaktest report from 2017
274 total water leak tests
244 water leak tests reports plus 30 tests not on the reported pass/fails as they included additional work
218 failed with reports showing leaks on first test. Several had to have the brand new system replaced due to excessive leaks found. I have actual number to leaks and retests if needed. 89.3% failure rate.
26 pass with no leaks. 10.7% pass rate.
30 additional to research. (Welder no-show, partial testing or additional cleaning up existing landlord installed duct, etc) that all showed failed, but no actual number of leaks so not part of totals.
The reasons for our position are very clear:
We have found that welding slag and/or construction debris and dust would cover up the small holes in the ductwork such that they are not discovered during light or smoke testing. For listed duct systems, the overlapping duct connections may prevent the discovery of leaks during light testing. When not properly tested, the leaks are not found until a later time when grease leaks out of the holes of the grease laden ductwork or worse yet, saturate the fire wrap or the fire rated shaft way (sheetrock).
I real life, the leaks are most often not found until the system is cleaned. The first cleaning removes the construction debris along with the grease accumulated in the ductwork. Many of these grease and cleaning solution leaks are not found until major damages occur, at which point fire wrap is saturated with grease and/or cleaning wastewater. Additionally, these leaks are often in concealed locations such as above ceilings or interstitial spaces. This saturation can limit or even eliminate the fire wrap’s fire protection capabilities and can allow fuel buildup to occur in protected areas.
Water leak testing provides insight that neither light nor smoke testing can duplicate. The water leak testing procedure, is effectively a cleaning of the duct before it gets contaminated with grease. As such, by performing this test, the testing agency can confirm if sufficient access is provided for cleaning and also provide evidence of proper slope of the duct.
This is based on both engineering opinions and over 20 years of ductwork leak testing by Enviromatic.