Do you ever get annoyed with how long it takes to get hot water at your kitchen sink? I
do did, up until last weekend. It used to take a full 45 seconds with the hot water turned on full blast before I would actually get hot water my kitchen faucet. With my kitchen faucet rated at 2.2 gallons per minute, that would equal a little over 1 1/2 gallons of wasted water every time I needed hot water at the sink.
I've considered a few different options to get hot water at my kitchen sink faster, such as installing a re-circulating pump or a point-of-use water heater - you can read about the details of these options at Home Depot's web site. I decided against these options because the installation would take too much time, and the materials alone would cost more than I was willing to spend. Thanks to an idea I read about in The Journal of Light Construction, I was able to significantly reduce the amount of time it takes to get hot water at my kitchen faucet, and the total cost of materials for this project was less than $40.
All I did was install a dedicated 3/8" water supply line from the water piping coming off the top of my water heater to the kitchen sink faucet. By installing this 3/8" water line, I've cut the wait time from 45 seconds down to 10 seconds. Part of the reason I get hot water so much faster is that the hot water doesn't need to fill up all of the main 'branch' lines to get to my kitchen faucet. The hot water line that feeds my kitchen sink consists of 17' of 3/4" tubing, then another 25' of 1/2" tubing. I've cut the total run down to about 25' by running the line straight to my faucet. The other reason this works is because a 3/8" tube has about 25% of the volume as a 3/4" tube.
You might think that this reduction in size would equate to lower water flow at the kitchen faucet, but it actually made no noticeable difference. The hot and cold water flow both seem to be identical. So what's the downside to this, and why don't more plumbers do this? It's a code violation. The Minnesota State Plumbing Code requires a minimum of 1/2" pipe to the kitchen sink. Because of this, I left the old 1/2" water line in place. When it comes time for me to sell my house, I'll probably just re-connect the old 1/2" water line to the faucet. It should take about 30 seconds.
Reuben Saltzman, Structure Tech Home Inspections