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CASE STUDIES

Columbia, Missouri-based Environmental Dynamics, Inc. (EDI) has twenty-seven years of experience manufacturing innovative wastewater treatment systems. The company is an integrated manufacturer of diffused aeration systems including diffuser technology, research and development, system engineering, and product manufacturing. The backbone of their systems is PVC pipe. The systems use aeration to treat wastewater; aeration relies on the natural removal of harmful materials using microorganisms requiring aeration.

"If you have ever had a fish tank, you're familiar with the use of a "bubbler" to aerate the water," says EDI Executive Vice President Randy Chann. "The principle is the same. EDI systems use oxygen in the atmosphere blown through a carrier pipe - PVC - to treat wastewater."

The use of a diffuser - a mechanical device that puts oxygen into water - is a common approach to water treatment. EDI's systems use mechanical aerators fitted with a special, flexible membrane to provide fine pore diffused aeration. The finer the bubbles created by the system, the greater the system's efficiency. PVC manifolds and headers provide the structural grid to hold EDI diffusers & membranes. The diffusers themselves are essentially mini systems of PVC with specific openings to feed flexible membrane.

The result is a remarkable PVC structure. The largest plants treat over 100 million gallons of wastewater per day. In each of these plants, the amount of PVC piping employed in the air distribution system and diffuser components is over 60,000 feet. In addition, each plant uses numerous fittings, tees, ells, caps, flanges etc. On large jobs this amounts to well over 2000 to 3000 miscellaneous fittings.

PVC DWV SYSTEMS AFTER 20-PLUS YEARS OF SERVICE

PVC Background
The earliest report this author found describing a PVC water pipe installation dates to 1934 in Germany. In 1950 a plastics pipe trade association was founded in the United States, and in 1951 a plastics evaluation program began at the Michigan School of Public Health. That four-year program included animal feeding studies and an impartial study of plastic pipe from a public health point of view.

In 1957 the US Department of Commerce published a Commercial Standard (CS 207 - 57) for PVC pipe. ASTM Standard (D 1785 - 60) followed in 1960. Other PVC pressure pipe standards followed (CS 256 - 63 in1963 and ASTM D 2241 - 64 in 1964) along with PVC - DWV Pipe and Fittings Standards (CS 272 - 65 and D 2665 - 68) in 1965 and 1968 respectively. PVC piping installed during and after those dates may be marked with those standard numbers.

Introduction
PVC DWV systems have been installed in multi-story buildings for more than twenty years. When these early installations were made in the late 1960s and 1970s, a list was compiled of 51 buildings in 31 cities. This article reports findings from 1998 inspections of six of these early installations, along with confirmations that the systems continue in operation at this time.

AIA National Headquarters Building in Washington, DC
This seven-story building was built in 1973. New chillers were being installed and the air handling system was being revised at the time of the 1998 inspection. The DWV and roof drain systems are PVC and have been trouble free. Very little of this piping is visible except in the seventh floor mechanical room where drain and vent pipes were observed. Some of them had expansion joints. Exposed cooling tower piping out on the roof had faded in color to nearly white. Mr. Pierre Rahel has been Building Manager for the last two years and Mr. Sid Cox has been the Building Engineer for the last seven years. They report that their PVC piping systems continue to perform satisfactorily.

Ellicott House in Washington, DC
This nine-story apartment building was built in 1973. The DWV system and the storm water drains are PVC. Robert Ducket has been the Maintenance Supervisor for about fifteen years. His staff uses normal preventive maintenance procedures and has had no problems with the PVC piping.

Cairo Condominium in Washington, DC
Stevens Company, Plumbing and Heating has done all the service work on the piping systems and has records of all the maintenance that has been required on this condominium. Some cracks have appeared in Tee/Wyes, but the company noted that these occurred when the branch line was not properly supported. Some cracks have also appeared in flanges, but otherwise the systems are working well.

Stevens Company uses a lot of plastic pipe in their repair and new work and reported that in its experience:
· Stoppages are about the same in cast iron pipe as in plastic piping systems.
· Piping laid against drywall creates sound problems.
· Screws and nails can penetrate piping. (This occurred mostly in bathrooms.)

Tower Villas Condo in Arlington, VA
At the time of the 1998 inspection the metallic hot water piping and the hot water heating system were subject to pinhole leaks (common in these metallic systems). Roberto Suarez who had been the Building Maintenance Supervisor for five years provided information about other plumbing systems. He reported that system maintenance had been normal except for one incident when a heavy rainstorm resulted in a complete separation of a pipe/socket joint in a 6-inch roof drain leader. This flooded the lobby area. No other information was available concerning the cause of this failure in a gravity flow pipe in service for years with no sign of leakage. Since 1998 management has made some improvements to the heating system, but continue to have water-piping leaks. The PVC systems continued in service without problems.

(Author's note - Without seeing the 6" joint that separated, but based on some past experiences, this joint could have been primed and assembled during the "fitting up" process but then never solvent cemented. This type of joint separation has been reported by others and has even occurred with pressure pipe. If anyone reading this has first hand information, please call Robert C. Wilging at (440) 933-4394).

Holiday Inn in McLean (Tyson Corners), VA
This nine-story building has cast iron stacks and PVC branch piping. There have been no problems with the PVC piping, and system maintenance has been normal. Some PVC has been used in remodeling and in a new building. Chief Engineer Barry Singh reported that about four years ago a CPVC fire sprinkler system was installed without any problems and is operating at 150 psi.

As of December 2000, all systems continue in service. However, one underslab line failed because the fill consolidated and caused a break in the line.

Park Layne in Dayton, Ohio
This eleven-story luxury apartment building was built in 1969 and was mentioned in the October 1970 issue of Building Systems Design magazine. The article refers to a "marriage" of PVC DWV and cast iron in the drainage systems.

The "marriage" reference applies to the Park Layne installation where PVC pipe 3-inches and smaller was used for all of the kitchen, lavatory and tub drains plus some of the shower drains. Cast iron vent pipes were used in the lower six stories, and PVC was used for the remainder of the vent piping. The PVC pipes are caulked into cast iron fitting hubs with oakum and lead wool. These joints were made without PVC molded adapters and have been trouble free.

During the same time, some of the cast iron pipe and fittings have developed corrosion leaks. Although epoxy patches can provide temporary relief for small leaks, replacing leaking pipe and fittings with PVC is a permanent solution. Shower drain leaks have been resolved by breaking out the concrete base, removing the cast iron drain piping and installing a new PVC drain line and a shower base. The PVC pipe is easy to cut, fit and join. Based on experience with PVC piping that has been in service for 30 years, these PVC shower drains appear to solve the corrosion problem.

The Park Layne with 128 apartments and two additional buildings, The Riverstone and The Rockwood, are owned and operated by Towne Asset Management Co. Larry Rainwater has been in the apartment maintenance field for 25 years and has had responsibility for all three buildings for three years. Based on his experience with all three buildings, Rainwater believes that his piping maintenance job would be easier if PVC DWV piping had been installed throughout. He also maintains the swimming pools and had has found the PVC piping used there has served well.

Note: Mechanical cleaning
During the 1998 inspection, Larry Rainwater noted that he sometimes goes through a section of PVC pipe with mechanical cleaning equipment to reach a section of cast iron pipe. (Author's note: A brief report about tests done years ago using RotoRooter equipment showed that the cleaning tools passed through PVC bends without damage to the plastic fitting.) Rainwater referred this inspector to Alan Pierce Sr. who has operated a RotoRooter franchise for 40 years. Based on his experience, Pierce offered the following comments on PVC maintenance with mechanical cleaning equipment:
· Acid and caustic drain cleaners, if used continually, will attack and destroy metal pipe, because after the metal is cleaned corrosion continues.
· Thin-wall PVC sewer pipe can be cracked by the whipping action of a sewer snake.
· Schedule 40 PVC DWV pipe and PVC sewer pipe are not affected by mechanical cleaning equipment.
· The gases inside DWV and sewer pipes create corrosive conditions that destroy metals over time.
· After some brief exposure to sulfuric acid, sewer snakes broke cast iron with brittle fractures even though they were only in service a short time.
· Proper sewer pipe installation is a major factor in obtaining a long service life regardless of what sewer pipe material is used.

Conclusion:
Although these inspections did not yield any significant new information, they did verify that PVC's corrosion resistance is a primary factor in its ability to provide many years of trouble free service in both DWV and sewer systems.

If any readers have information that will further this effort your response to the Editor would be appreciated.