Instant hot will scald you. The output temp is, what, around *180F?

How about a small (5 gal) water heater under the sink in line with the hot supply?

Instant Hot has temperature range 140°F - 190°F. 140°F should not scald. Actually, my current IH is even colder - just right for hand washing, except for auto-off feature.

"How about a small (5 gal) water heater under the sink in line with the hot supply?"

This is called "point-of-use water heaters" and it appears to require professional installation, permit, inspection and discharge pipe. If you know of a model, which does not require these, please, let me know.

Anything over 120 °F can scald. An instant hot, unless its heater is failing and can no longer produce the temperatures for which is was designed, is not appropriate for hand washing. Further, an instant hot falls under the same regulatory requirements as a small water heater - the vented faucet provides the same protection as the over-pressure pipe in a small water heater. Just do it correctly and install a POU water heater plumbed to your regular faucet.

Stiebel Eltron has a new tankless heater for hand washing that plugs into a standard 110 outlet. It's shown on the home page of their web site. www.stiebel-Eltron-usa.com.

jhnlmn-

From The Burn Foundation:

Hot Water Causes Third Degree Burns…
…in 1 second at 156º
…in 2 seconds at 149º
…in 5 seconds at 140º
…in 15 seconds at 133º

Why everybody so focused on burns? I am telling you that my instant hot makes lukewarm water. It cannot burn. But the main house heater, on the other hand, does make pretty hot water (after a minute of flushing), which, in fact, does cause burns. It works like that: I open water, water is cold, start applying soap, stick hand under water - burn. This is a real problem, not the lukewarm water from the instant hot.

However, my question was not about burns, it was about installation, pressure release pipe, permits and regulations.

Thank you

Apparently different models have different temp. I was looking at Wasteking, that lists 140-190 range. Water heaters can go up to 160F, so there is an overlap.

Well, if you turn that one down all the way to the bottom of its range you would still have 3rd degree burns in 5 seconds. A water heater is an entirely different appliance and the water typically travels through some length of plumbing where it is cooled on the way to the faucet and gradually warms up to its set temp. An instant water dispenser is point of use, so you have almost no lag before it starts coming out at the set temp.

jhnlmn - Just look at your local plumbing code to find your answer, or hire a local plumber. The reason folks here are focussing on burns is because you appear to lack the ability to understand temperature and its relation to burns. I'll try one more time: Go look at your water heater. What is the temperature setting? If your regular hot water is burning your hands, you can do one of two things - 1) set the water heater temperature lower, 2) wash your hands with a mix of hot and cold rather than placing the faucet all the way on hot. At least you have that ability with a normal faucet. With an instant hot you will have no ability to mix and, if it is functioning properly, IT WILL BURN YOU. The fact that your current one isn't burning you is not relevant - clearly it is not functioning properly.

Now, go do whatever you want to do because you are, of course, under no obligation to take advice. (Just keep a tub of ice water handy to plunge your burned hands into in the event of a scald)