To make sure you're not testing too early, assume the sperm had very long lives (5 days is considered a very long sperm life) and that conception occurred then. Then allow 14 days for the embryo to implant and develop enough hCG to show up on a pregnancy test (96% of pregnant women will test positive by then.)
A gas water heater will recover in half the time of an electric unit. A 40-gallon gas water heater can recover in about an hour. Recovery for a 40-gallon electric water heater takes about two hours.
Cost to heat water in a gas tank. 1  A typical gas tank water heater is only 59% efficient. 2  So it takes 525 Ã· 59% = 890 Btu's to heat a gallon of water in a gas tank. 3  One therm is 100,000 btu's. 4  So one Btu is 0.00001 therms. ( 5 Pacific NW Natl. 6  Lab.