Then "those people" should do what I did; installed a "tempering valve" so that the DHW stays below a scalding temperature.
I do feed the dishwasher from a point ahead of the tempering valve though, to get the hottest water in it fastest.
Jeff
May I ask what tempering valve you used? I'm considering doing exactly that. Set water heater to 140 F, put the vanities and shower on a tempering valve at 110 F or so, use 140F for the dishwasher and clothes washer (I wash sheets in hot to kill dust mites) . I'm not sure about the kitchen sink. I'm also unsure if it is better to have two different hot water piping systems (hot and hotter) with a single big tempering valve, or install individual tempering valves at each fixture. Since I'm redoing all the plumbing, I can do either.
Cheers, Wayne
With "instant on" via a pump and a conventional tank water heater, you still may want to raise the hot water temperature on the tank to increase the heat storage and not run out of hot water as quickly.
Cheers, Wayne
I think your problem is that you have a large amount of water that cools, and you have to wait until that is displaced by heated water before you get hot water at the faucet.
It follows that your supply line is too long, or too wide. Take a look at it. If it is routed indirectly, shorten it; if it is 3/4, replace it with 1/2 inch. I think insulation won't help much as it will not keep the water in the line hot overnight, or when it is not used for a few hours.
I solved a similar problem by running a second line from near the farthest faucet back to the bottom of the water heater, forming a loop. I insulated the supply line and left the return line uninsulated, and a check valve prevents backflow. Since the supply line is insulated, the water in there remains hotter. When it cools, it is forced through the return line to the heater. This works for me because I have a multi-story house (long vertical runs), I was able to install it easily when we were doing a tearout remodel of the bathroom, my plumbing is all indoors, and I live where we have far more heating degree days than cooling days. There is some inefficiency as it is like a radiator, and I have to heat a little more water than before, but on the other hand it uses no electricity and less water than before, and runs constantly and silently. I have had it in over two years now, and I am still amazed at the instant hot water, what a luxury!
Yes, there should be a dedicated return that goes back to the cold water inlet of the water heater . Put a check valve in the return line so the water can't go the wrong way when the pump is off. Use a stainless steel or bronze or hi temp plastic pump. I see a lot of people use iron body pumps to save money, they die quickly & put rust in the water. you can also return to a tee installed at the drain valve on the water heater. Easier to do with a crawlspace or basement than with a slab. Sonetimes you have to go back into the cold line under the sink, but that can cause problems, like putting hot water into the toilet & cracking the toilet tank due to water temperature shocking the tank.
Stretch.
Why? What is the difference between instant and regular at the same temperature?
Those people are stupid. The beauty of instant is that you don't have to set it hotter to have more, you have all you need.
I used a 3/4" Watts tempering valve, they're available at any plumbing supply center. They have a knob adjustable temperature seting. The thermostatic guts are a little like those in an automobile engine coolant thermostat and can be easily changed out if and when they fail without having to break out the soldering gear. I've had to stick in new parts once after ten years of service, it's coming up on twenty years now and it's still working OK. Wish I could say the same for our electric water heaters, I can only get about six years out of them before something starts leaking.
Jeff
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