Contractor uses blown epoxy lining system to rehabilitate waterlines in a large apartment complex.
A general contractor renovating a 15-story public housing project in St. Petersburg, Fla., noticed drain stack problems in two of the three apartment towers. He called Michael Larson of Florida Pipe-Lining Solutions in Sarasota.
|Air hoses from the compressor and dryer run up the side of an apartment building to the eighth-floor control room. Clear hoses coming down from the 15th floor go to the separator and dust collector.|
As Larson's crew evaluated the situation, they found fixtures from the fifth floor down with little or no water pressure, and most were gummed up after standing idle for two years. Any water sputtering out was brown with rust. The focus of the project shifted to the water pipes because they were the pertinent issue.
"The contractor had pipe samples from 18 months of remodeling and making mechanical repairs," says Larson. "The 1-inch trunk lines were up to 50 percent occluded and some half-inch branch lines were completely encrusted. My first concern was how to get air through the pipes to sandblast them."
Larson chose the ePIPE process from ACE DuraFlo Systems to rehabilitate the galvanized pipes with an epoxy lining. Instead of being one of the first contractors on-site, however, Larson's crew found themselves near the end of the project with 50 other workers from five subcontractors racing toward the finish line.
"The developer, wanting to fill residencies as soon as possible, imposed a very tight timeline," says Larson. Despite the congestion and heightened risk factors, they restored the North and East Tower water systems, including branch lines to all 348 units, in six months.
The top-fed piping system had 3- and 4-inch mains, 1- and 2-inch trunk lines, and 1/2- to 3/4-inch branch lines. Six workers transported a sandblasting unit, two air headers to regulate pressure, and an epoxy dispenser to a control room on the eighth floor. From there, they worked down to the first floor and up to the 15th floor. The Atlas Copco 1100 air compressor (1,059 cfm/290 psi) and heated Ingersoll-Rand desiccant dryer remained outside the building.
|From the header in the control room, 1-inch red hoses run up and down the stairwell to all 15 floors.|
To prevent the two heavy 2-inch air hoses and exhaust hoses from kinking or swaying along the exterior of the building, the crew fashioned brace arms with 90-degree bends from galvanized fittings. They mounted them on every third floor just inside apartment windows, with arms protruding out to restrain the hoses.
Exhaust hoses ran out a 15th floor window to the ground. Workers secured them to a six-hole flange with 4-inch Tapcon screws in the concrete roof. To hoist the air hoses, two men in the control room lowered a rope, then hauled up the attached hose while members on every other floor manually controlled sway.
The air-driven process used a compressor feeding air to the dryer, which reduced the dew point (moisture in air) to a range of minus 10 to minus 100 degrees. "The air must be absolutely dry for sandblasting and injecting the epoxy," says Larson.
In the control room, the air hoses connected to two air headers, each with 16 ports for 1-inch hoses connecting to individual floor manifolds with five ports. The manifold, with individual valves, fed air through 1-inch hoses to fixtures (sinks, toilet, tubs). "We had two supply hoses on each floor and 32 manifolds," says Larson. "Approximately two miles of 1-inch air hoses congested hallways and ran up and down stairwells to all 15 floors."
Another 1-inch hose supplied air from the header to the sandblaster. The air, introduced at 60 to 80 psi, mixed with 50 pounds of aluminum oxide in the hopper and was delivered to the manifold and hoses, which were hooked to connections with Chicago click-and-twist fittings. Workers cleaned from the 15th floor down.
In the closed-loop system, vacuum from the dust collector pulled debris and air into the 2-inch exhaust hoses on the 15th floor, then down to the separator. Large chunks dropped out, while air continued into the dust collector where two large commercial filters removed particles and released clean air.
|The Atlas Copco 1100 air compressor pushes air through the Ingersoll-Rand desiccant dryer to remove any moisture from the pipes before lining.|
"Our biggest challenge was getting air into the blocked half-inch branch lines on the first to fifth floors," says Larson. The labor-intensive, slow process involved injecting small amounts of air at the connection, then reversing the flow to suck moisture from the incrustation. Accessing the branch lines required working in tight quarters, with the crew hugging toilets and climbing into kitchen sink cabinets to reach the pipes. When the scale looked dry enough to break loose, they hit the pipe with a hammer and vacuumed out the debris.
Workers cut into finished and unfinished walls to replace the piping in cases where they couldn't establish an airflow channel for sandblasting. "We found the worst conditions in studios with a single bathroom and kitchen," says Larson.
To prepare the surface for the epoxy, they cleaned the pipes to bright metal. "Penetration is always a problem when dealing with pipes this bad," says Larson. "Sandblasting causes holes the diameter of pencils that epoxy will not seal, and they usually occur at the back of 90-degree elbows."
The crew rehabilitated 150-foot hot- or cold-water risers one at a time. Each fed a back-to-back bathroom or kitchen group. "Risers were usually 2 inches at the 15th floor reducing to 3/4 inch at the lower floors," says Larson. "Drying the scale and sandblasting each took three hours, then we applied the coating." They also changed out all the ball valves and sink angle stops (shut-off valves).
Rumble and roar
The ANSI/NSF Standard 61 certified epoxy was shot through the same hookups, except that workers disconnected the air hose from the sandblaster and hooked it to the epoxy dispenser. The machine mixed resin and catalyst from two cylinders at 50/50, then a foot pedal dispensed 100 mL per shot into a clear 1-inch tube 6 to 10 feet long.
A technician brought the tubes to a floor manifold, closed all the valves, and removed the hoses from the manifold to the connections. He connected the tubes, charged the manifold, opened the valve to a tube port, and injected the epoxy. "For a 16-mil coating, a 100 mL shot goes 15 feet in a 1/2-inch pipe and 10 feet in 3/4-inch pipe," says Larson. "Based on those distances, we calculate how much epoxy to pump into the tubes."
Lining risers began by shooting from the first to second floor, then advancing a floor at a time. "We could hear the epoxy moving through the pipe and knew when it arrived at the connection," says Larson. "After the epoxy set for 24 hours, we pressure-tested the riser at 80 to 120 psi for two hours. If we lost a lot of pressure, we injected continuous air at 120 psi and stationed guys in every unit to listen for it escaping."
|A 2-inch trunk line with a 16-mil ANSI/NSF Standard 61-certified epoxy coating.|
With the proper apartment identified, workers pulled a shower trim plate, inserted a RIDGID mini SeeSnake into the wall, and looked for leaks. Epoxy on the wall – usually by a 90-degree elbow – was a dead giveaway. They then cut through the drywall and replaced the fitting.
Flushing the risers was the final test. As water ran through fixtures and down drains, it occasionally flooded the room. "We knew we weren't at fault because the coating had passed the pressure test," says Larson. Cutting through the walls revealed 10-foot-long by 1/2-inch-wide cracks in drain stacks. This happened regularly, but the company didn't have the contract to repair them.
Workers completed two back-to-back bathroom and kitchen risers per week. As soon as they finished, the units were occupied. "In certain places, increased pedestrian traffic made it necessary to hang the hoses to clear hallways," says Larson.
The transformed government housing project is now home to college students, interns at nearby hospitals, and young professionals.