We recently replaced the water heater in our home. The setup for the water heater also provides the water to heat the home, which it blows out the ducts. Since we replaced it, we can only seem to get really hot water if the heater is on blowing out the air. Otherwise if it isn't on, it is only luke warm that lasts a few minutes and eventually goes cold. There is also a thermal expansion tank installed. I performed a psi check on that and I couldn't get a reading with a tire gauge. I'm not sure if because that tank is possibly bad, it is making this problem occur (hot water not getting pushed into the house and out the faucets unless the heater is on).