How long should wait hot water to get 30' from tank?

wynswrld98April 5, 2013

I have an electric tank water heater in the garage that services the kitchen and a couple of other things in the house in the same general area. The house has a tankless gas water heater on the other end of the home that services the showers on that end of the home.

It's taking about 45 seconds to get hot water to the kitchen sink, the distance from the water heater to the kitchen sink is about 25-30' (ofcourse no knowing what path the water line is running since it's behind drywall).

What would anyone guess is a reasonable amount of time to get hot water to the kitchen sink based on this kind of setup?

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For your system, with your pipe size and your flow rate?

About 45 seconds.

If you are interested in the non-smartass answer:

You didn't provide your pipe size or the age of your faucet so I will make the following assumptions:
(1) Faucet was purchased after 1994
(2) Pipes are 3/4" copper
(3) You've got about 40' of pipe

Modern faucets have a max flow of 2.2 gpm. That amount of water travelling through 3/4" copper pipe travels at 1.46 ft/s. If the water traveled along in a perfect slug with no mixing, it would take a 27.4 seconds to exist your faucet, but it doesn't. Some mixing, and therefore cooling, takes place at the lead edge. In addition, the water is losing heat as it heats up the copper pipe along the way.

If your pipe is 1", 2.2 gpm would travel at 0.86 ft/s and take 47 seconds plus the extra time for heating the pipe and mixing with the cooler water.

Of course, YMMV if your faucet allows less flow, pipe diameter or length is different, etc,

    Bookmark   April 5, 2013 at 6:35PM
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Brand new faucet spec for it is 2.2 GPM, pipes are 3/4" copper.

So it sounds like what I'm experiencing is normal. It's funny because as you are at sink waiting to wash your hands or rinse dishes it feels like it takes forever to get hot water but timed it at 45 seconds.

    Bookmark   April 5, 2013 at 10:07PM
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