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The WET Study - A Monumental Achievement in Restoration

January 15, 2004
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During 2003 a group of volunteers from the ranks of the International Society of Cleaning Technicians undertook a rather ambitious project they termed the Water Extraction-efficiency Test, or "WET" study.

They solicited the assistance of Carey Mitchell, ISCT director and director of technical services with Shaw Industries, and the staff of Shaw Laboratories in Dalton, Ga. The study was overseen by Mitchell and Ruth Travis, the president of the ISCT. Neither Travis nor Mitchell sell equipment, teach water-restoration schools or practice water-restoration services, enabling them to transcend the inevitable bias the other participants brought to the table.

The WET study was planned in the fall of 2002 and implemented in January 2003, with follow-up testing in July. In addition to Travis and Mitchell, participants included IICRC-approved water-restoration instructors Barry Costa, Joe Dobbins, myself, Chuck Dewald, equipment manufacturer representatives Bret Bartholmey, Kurt Bolden and Tom Kingman, and statistician Jud Savelle.

The idea behind the WET study is to test the ability of various industry tools and machines to remove water from both carpet and pad - what we refer to as "in-place" drying of Category 1 "clean" water losses. The team tested both truck-mounted and portable extraction equipment. Over the year-long test period, four types of carpet and the most common residential pad were tested.

  • 24-ounce nylon Saxony over 7/16" bonded urethane (the largest selling carpet style).
  • 28-ounce 90 percent olefin/10 percent nylon Berber over 7/16" bonded urethane - an extremely popular residential carpet style.
  • 49-ounce nylon frieze over 7/16" bonded urethane - representative of high-end carpet found in homes.
  • 41-ounce olefin multi-level loop over 7/16" bonded urethane - a difficult style to extract.

    Contrary to popular belief, wet-weighing proved that both the carpet and pad hold from 2.96 to 4.92 gallons of water per square yard.

    The WET team used both truck-mounted and portable extraction units. The truckmount, even with 100 feet of vacuum hose, provided the most consistent vacuum efficiency overall in terms of both lift and airflow. The WET Study Appendix contains an examination of the components and vacuum efficiency, and how to maximize the use of any extraction unit.

    The portables used contained two vacuum motors, configured as two two-stage vacuums or two three-stage vacuums, with both systems in parallel series. The shorter the vacuum hose and the larger the diameter, the better the extraction efficiency appeared to be. In fact, a proprietary "portable" unit with two three-stage vacuums positioned less than a foot from the carpet consistently out-performed the truckmount.

    The WET team got very good at destroying carpet and pad, completely demolishing 24 9-by-12 sections (3,500 square feet) of carpet and pad (donated by Shaw) in order to obtain three sets of data on each carpet style. While it is impossible to cover the entire 51-page published study in a single article, there were valuable lessons learned about each tool's efficiency. For instance:

    Light Wand
    This probably is the most popular tool used today on water-restoration claims. Why? Because every truckmount or portable unit includes one. It's a highly maneuverable, lightweight tool that is used efficiently in most carpet cleaning. The main problem is that it doesn't extract water very well, at least not from cushion under carpet.

    The light wand does fine when it comes to extracting water from direct-glue commercial carpet or when doing a containment extraction during "loss mitigation" to keep excess water from migrating to dry areas. But for extracting water from pad, it was the poorest performer.

    When extracting the 28-ounce Berber, the light wand removed 34 percent of the water. Of the 296 gallons contained in 100 square yards of carpet and pad, the wand left 196 gallons, or 66 percent. Of the water removed, 85 percent came from the carpet, while only 8 percent was removed from the pad underneath. That tells any professional that, if you're going to use that tool, you'd better be planning to remove the pad as well, thereby increasing the cost of the restoration project by some 25 percent to 30 percent overall.

    Bottom line, if you're going to engage in "state-of-the-art" water extraction, you simply can't do it using a light wand.

    Drag Tool
    We used two weighted drag tools, one with a compression roller build-in and one that was followed by compression rolling after each extraction pass. While both did better than the light wand, neither knocked our socks off. The weight of the drag tool and the seal created against the carpet had a significant impact on extraction efficiency.

    The tool with the roller built in was rather awkward to use. Although it has plenty of weight on the extraction head (100 pounds plus), technicians are forced to maintain a very delicate balance between the compression roller and the extraction head. Much of the desired weight on the head transferred to the roller, making total extraction somewhat spotty. The rigid hose connector and the difficulty in adjusting the handle to the technician's height further complicated the tool's use.

    The second drag tool weighed about 45 pounds, an insufficient weight to maintain a consistent seal against the carpet. This resulted in airflow through the pile with a sacrifice in deep extraction from the pad under the carpet. This is why both drag tools were excluded from tests using portable extraction units with lower vacuum power.

    Rotary Extraction Tool
    One rotary cleaning machine was used to test its extraction efficiency. While its performance when used with the truck-mounted extraction unit was comparable to the drag tools tested, when used on cut-pile styles with no detergent lubrication (as in cleaning), there appeared to be some yarn distortion. Furthermore, of the tools tested in a previous latex lamination strength test, the torque on the carpet pile applied by the rotary extractor appeared to have a minor negative affect.

    Stationary (Stand-on) Tool
    Two "stationary" extraction tools were tested. One had a 2-inch hose connector mounted at a 45-degree angle directly on its extraction head, while the other had a 1 ?-inch connector welded at a 90-degree angle halfway between the T-grip and the extraction head. The combination of the size of the plumbing, the severe angle and the distance from the wet carpet and pad seemed to create a significant disadvantage for the latter tool.

    Both tools performed well on the 24-ounce Saxony, while a significant difference between the two was experienced on the 28-ounce Berber and the heavy-density frieze and multi-level-loop carpet styles.

    It is significant to note that, with any stationary extraction tool, moisture pulled from the pad is left in the face yarns of the carpet due to airflow that is significantly higher around the perimeter of these tools. The remaining moisture in the face of the carpet pile is estimated to increase drying time by 12 to 24 hours or more. Therefore, follow-up light wand extraction is essential to efficient use of stationary tools.

    Self-Propelled Tool
    The WET team tested the industry's only two self-propelled extraction tools, one of which moved significantly faster over the carpet than the other. On the 24-ounce Saxony, extraction efficiency was comparable; however, on the 28-ounce Berber with four passes, there was a notable difference in extraction efficiency. It took eight extraction passes with the faster tool for it to begin to catch up with its slower peer.

    Similarly, the slower tool, set on a high-speed setting and making six passes, was generally outperformed by itself when set on its slowest speed and making only four passes. The conclusion drawn from both data sets is that, as an industry, we are moving entirely too fast in the extraction phase of the application of the "Principles of Drying" outlined in IICRC S500. And since extracting water is about 1,000 times more efficient than evaporating it and removing vapor from the structure with dehumidification or ventilation, a little more time spent extracting water on the front end of job processing can trim a day or two off the total time required to return a structure to a pre-loss dry state.

    The WET study is a monumental contribution to industry knowledge. It represents what trade associations can do when creative leaders and volunteers have their finger on the pulse of industry needs. The purpose of the study is not to "declare a winner"; many considerations must be made in selecting a tool. Size, weight, price, vacuum source requirements and speed of extraction, as well as efficiency, all factor into the decision. It would be a mistake to assume that this article does justice to or substitutes for the 51-page test report with data sets. The more I read and analyze the report, the more I learn.

    The WET Study is a must for serious water-restoration companies as part of a comprehensive training program. To obtain a copy of the entire report, contact the ISCT at 1-800 WHY-ISCT (949-4728).

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