Does hot water take so long to reach the bathroom/faucet furthest from hot water heater simply because of the distance or because the temperature of the pipe all along the route steals the waters heat?
In: Engineering
That’s a good question. Here is my view.
When you first hot water faucet on, the water temperature goes in three phases: First, it is cold. After many seconds or a minute or more, in the second phase, the water rises in temperature over 20 to 30 seconds. In the third phase, the water is hot and continues to flow hot.
In the first phase, the cold water that resides in the pipe is pushed out. The further away, the longer it takes to flush the cold water out.
In the second phase, the water is mixing, Because inside of the pipe is laminar flow, the water in the center of the pipe moves faster then the water close to the pipe wall. It thus take some time for the cold water to get pushed through. During this time, the pipes are getting warmer from the water flowing through them.
In the third phase, the hot water flows in steady state. Yes, some heat is being lost through the pipe, thus the water at the tap will be a tiny bit cooler than when it exits the water heater, but this heat is relatively small.
The reason why I can say that the heat lost is relatively small is because I insulated the hot water pipes in my house, and there was not noticeable difference.
Latest Answers