Adding Load to an Existing 1/2-Inch Gas Line
A homeowner in unincorporated Clark County is adding a 60,000 BTU/hr pool heater and a 45,000 BTU/hr freestanding range to an existing gas system. The meter outlet is 7 inches water column and feeds a 1/2-inch black-iron line that runs 45 feet with seven elbows to an 80,000 BTU/hr furnace and a 40,000 BTU/hr water heater. The longest new run to the pool heater would add 30 feet and four elbows. The homeowner wants to tee off the existing 1/2-inch line at the furnace and use a flexible connector to the range. The gas company says the meter can deliver the added load, but the homeowner has no sizing calculation. The local inspector requires a permit and a pressure test. The homeowner asks whether the existing line is large enough and what else must be installed.
1. Determine whether the existing 1/2-inch black-iron line can carry the added load. Show the method you would use.
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The connected load is 80,000 + 40,000 + 60,000 + 45,000 = 225,000 BTU/hr. Meter capacity is not pipe capacity. Use the longest-length method in the adopted fuel gas code: measure from the meter to the farthest appliance, including an allowance for fittings and elbows. A 1/2-inch black-iron line at 45 feet with seven elbows cannot carry 225,000 BTU/hr at 7 inches w.c.; it is likely limited to well under 100,000 BTU/hr. The existing 1/2-inch line is therefore not large enough for the added load. A likely solution is a larger trunk, often 1-1/4 inch or as calculated, with dedicated branches to the furnace, water heater, range, and pool heater. If the system operates at 2 psi, a regulator is required at each appliance. Do not tee the range and pool heater off the existing 1/2-inch line.
2. What appliance connections and safety devices are required at the range and pool heater?
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Each appliance needs a listed shutoff valve in the same room and within the required distance, a sediment trap or drip leg downstream of the shutoff, a union or approved connection, and a listed connector where one is used. The range connector must not be concealed and must not pass through a wall; the outdoor pool heater needs a shutoff, sediment trap, and protection from weather. Follow the manufacturer instructions and the fuel gas code. The drip leg is not optional. Also verify clearance to combustibles and the combustion and ventilation air for the pool heater.
3. What testing and bonding steps apply before the gas is turned on?
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Obtain the permit and isolate the meter before testing. Test the new and existing piping at the pressure and duration required by the adopted fuel gas code and the AHJ; a common test is 10 psig for 15 minutes for low-pressure systems, but confirm locally. After gas is introduced, check joints with an approved leak detector. If CSST is used, bond the gas piping per the manufacturer and code, and never use gas pipe as a grounding electrode. Schedule the inspection before concealment.