[EQUATION IDENTIFIER] For 1-inch pipe: Δ H = 10 feet 100 feet × 0.2 inch w.c. = 0.02 in. w.c. For 3/4-inch pipe: Δ H = 10 feet 100 feet × [ 0.5 inch w.c. + ( 110,000 Btu/hr - 104,000 Btu/hr ) ( 147,000 Btu/hr - 104,000 Btu/hr ) × ( 1.0 inches w.c. - 0.5 inch w.c. ) ] = 0.1 × 0.57 inch w.c. = 0.06 inch w.c.