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.
How long does it take a new water heater to heat up? My cousin, who lives a couple of hours away, installed a new 50-gal. electric water heater for me today. He finished the job around 2:00 p.m., and I don't have hot water yet (at almost 8:00 p.m.).