Hi everyone- I have a 2.5 year old home, and recently out of warranty ran into a problem with the tempering valve or mixing valve that mixes cold water with the hot output to provide 60 gallons of hot water from a 40 gallon tank. Ok, so wife turns on the hot water- my son had just went out on his bike and left the garage door open. It sounded like a goose, honking was in my garage- carefully opened the garage door from in the house- and no goose- lol Went downstairs to find that the tempering valve was clogged and screaming like- you guessed it- a goose!!They are apparently non-serviceable- so removing the tempering valve was a little messy(remember to turn off the main water inlet!!)after the excess water was caught in a bucket- removed the valve- Went into the garage with the wife`s laundry on hold. Fired up the compressor and tried to blow through the cold inlet side- nothing. Hot side, blew through no problem.Went to a local hardware store website, found a replacement valve for $82 plus tax- $100 total. Then realized since we have hard water here and no whole house water filter, that calcium buildup was the culprit. Got my CLR , pressed in the clogged hot water inlet, filled with CLR, let it sit for half an hour. Rinsed in a bucket of water, re-installed, turned the water back on, a little better but not great. Cycling the taps between hot and cold, moves the cold water in pulses to the cold inlet side of the tempering valve- then poof, full steady stream of hot water.The calcium buildup and clog was gone! Figured this post would help save people money, just be patient and take your time. While the valves are non-serviceable, they are from the outside , and this worked like a charm for me, hope it will help you too! Have a great day!