Failed Gas Piping Pressure Test and a Confined Water Heater Closet
A tenant build-out includes a new 1-1/4 inch Schedule 40 black steel gas line, 95 feet from the meter to a 250,000 Btu/h packaged rooftop unit. The contractor pressure-tests the new line with air at 3 psi using a 0 to 15 psi gauge marked in 0.1 psi increments. After 10 minutes the gauge has dropped from 3.0 to 2.7 psi. The ambient temperature in the space rose about 15 degrees Fahrenheit during the test. The contractor soaps every union and threaded joint and reports no bubbles, then argues that the gauge drop is caused by thermal expansion and should be accepted. In the same suite, a 60,000 Btu/h natural-draft water heater sits in a closet measuring 5 by 6 by 8 feet. The closet has a 24 by 30 inch louvered door and a 1-inch undercut, but no outdoor-air openings. The contractor says the louvered door provides plenty of combustion air. The water heater flue is single-wall for 4 feet before entering a listed double-wall vent.
1. Is the pressure test acceptable? Explain the reasoning, including the effect of temperature.
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The test is not acceptable as reported. A 3 psi test held for 10 minutes is the usual minimum for this kind of low-pressure system, but the observed drop of 0.3 psi is three times the gauge's smallest division and is far beyond reading error. The temperature argument runs the wrong way: if the air in the piping warmed by about 15 degrees Fahrenheit at constant volume, the pressure would rise, not fall. A drop therefore points to leakage, a gauge or connection leak, or an unisolated appliance or valve, not to expansion. The soap test is also weak evidence because it covered only unions and threaded joints; it did not cover the entire test boundary, and some leaks are not accessible for soap. I would require the contractor to isolate the gauge and any appliance connections, verify the gauge, and retest the new piping at the required pressure for the required duration. If the gauge still falls, the line must be repaired and the test repeated. A written test record identifying the medium, pressure, duration, gauge, and observer should be part of the inspection file.
2. Evaluate the combustion-air provision for the water heater closet. Show the calculation.
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The closet volume is 5 by 6 by 8 feet, or 240 cubic feet. Using the customary indoor-air allowance of 50 cubic feet per 1,000 Btu/h, a 60,000 Btu/h appliance needs 3,000 cubic feet of volume. The closet is therefore a confined space by calculation. The louvered door does not automatically solve that. If the door is intended to draw air from the adjacent interior space, the combined volume of all connected spaces and the permanent openings must be evaluated, and the openings must be sized for the input. Using the two-opening method, each opening is typically 1 square inch per 1,000 Btu/h when directly connected to outdoors, so 60 square inches each, with one opening near the top and one near the bottom. The 1-inch undercut gives only about 30 square inches and is at the bottom only. The louvered door's free area depends on the louver type, and even a generous free area does not create outdoor air if the adjacent room is itself closed. I would require either two properly sized openings to outdoors, or a documented indoor-air path with adequate volume and openings, and I would verify that the flue draft is stable with the door closed.
3. What reinspection steps and documentation would you require before signing off?
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For the gas line, I would require a successful retest at the specified pressure for the specified duration, with the gauge isolated from the supply and the test boundary clearly identified. I would witness the test if possible and record the starting pressure, ending pressure, time, temperature, and gauge serial number. For the water heater, I would require a combustion-air calculation and the installed openings, then verify draft at the flue with the door closed and with the clothes dryer or exhaust fans in the suite operating. I would check the single-wall connector clearance to combustibles and its slope toward the vent, and confirm that the connector does not pass through a concealed space. I would also verify the gas appliance connector, sediment trap, shutoff valve, and access to the closet. The final approval should be conditioned on both the piping test and the combustion-air correction, because passing one does not cure the other.