Hoping to get some help on why the hot water in my master bath doesn't stay hot at night. My house is single story, 1500 sqft, with 2 baths. I have a 40 gallon water heater, installed in June 2011. There are 4 people in the house. I tried running several scenarios to try and figure out what is going on. Hoping I can get some suggestions here. The master bath stays hot in the morning, but at night, the hot water will stay hot for a couple minutes, then turn luke warm...almost a little cold. Thinking my hot water heater was just running out of hot water, I tried taking a shower in the 2nd shower (it's a little closer to the water heater) at night time as well, and it was hot the whole time. I rarely run the dishwasher at night, and I'm not running a clothes washer. I give the kids 1 bath around 7pm. My wife showers around 8pm. Sometimes it's already luke warm by this time. So again, i don't think the hot water heater is running out of capacity. I also removed the anit-scalding valve in my master shower, but no difference. Is it perhaps the hot water pressure not strong enough? My pressure was too high, and i had a plumber install a regulator to get it back to normal about 5 months ago. Any suggestions are greatly appreciated!