I have been searching and wondering if an industrial water chiller (https://industrialwaterchiller.com/) would work....what does anyone think?? I haven't called the company yet, but thought this might solve my arizona warm tap water problem....
There are different types of heat exchangers. I do not think you want to cool everything (no need to try and cool water to the water heater or hose bibs).
For liquid or a high mass one of the best methods I have supported is a liquid to liquid heat exchanger. A glycol solution is cooled with a standard compressor and expansion coil in the tank (the tank size depends on the load cycle) when you use water the water in the coil is cool 34-? And as warm water enters the coil the heat is moved into the glycol solution, as the tank of glycol warms the compressor turns on and maintains the glycol temp.
The smallest liquid to liquid was under 1 gallon and the largest about 75-100 gallons. As most homes use a limited amount of cold at a time this type system may be all that is needed and a well insulated tank using this method was the highest efficiency type of system as the tank stored the cold so the compressor could be smaller using less energy and less chance of freeze up.
Deeper water main - and longer if possible
The cheapest option is to re-trench the water line from the street to your house. This is probably a good idea anyway due to climate change resetting all our assumptions about where freezes occur.
The Minnesota code book calls for burying water mains at 80 inches (6'8") to get below the frost line. So that's what you do. For the water line from the street to your house, go ahead and bury at that depth. And feel free to make a zig-zag route... the farther the better. What you're after is maximum possible pipe skin area. Also ideally, use copper for good heat transfer - I wouldn't normally splurge on such an expensive metal, but you are ready to buy a commercial chiller!
At that depth, the ground will be a great deal cooler. The copper pipe and long run will assure good thermal transfer. So the water should arrive at a reasonable temperature.
A cheaper way to do this, if you have a bunch of conditioned utility space, is just run hundreds of feet of copper pipe, going back and forth and back and forth in the conditioned space. This will be an ad-hoc, home-brew water-air heat exchanger, which will passively cool the water in the pipe toward ambient temp in the room. This will need to be exposed, no way to conceal it since it needs air circulation to work.
Another way to accomplish this same thing is by a vertical shaft - send the water down the vertical shaft and bring it back up. That seems like a pretty weird item, but they are used for heat exchangers for ground-sourced heat pumps.
Speaking of heat pumps...
What you really need is a "cold water tank" sitting right next to your "hot water tank". Ideally, they will be two tanks but only one Freon engine, so it is pumping heat out of the cold water tank into the hot water tank. But it could be two Freon engines in the same room interchanging air between them.
A deeper water line may not help in Arizona, as the soil temperature is consistently higher there than in northern states like Minnesota. This article gives temperatures of 80°F in Phoenix, although 70 may appear in the state:
The ground temperature at 15 feet down in Phoenix is 80 degrees as opposed to 70 degrees in central Arizona or even less than that in Northern states.
I did a quick search and was getting temperatures around 50°F in states like Minnesota. Obviously a temperature of 50°F will deliver nicely chilled water.
Note that fifteen feet is quite deep to bury a pipe. So your pipe may be more shallow than that and therefore warmer. If the line at the road is only six feet deep, then it probably won't help to lower the line from there to the house.
People in Alaska have the reverse problem. There, if you go below what they call the permafrost line, your pipe will freeze. Because Alaska's average temperature on the year is below freezing. Minnesotans are more fortunate in that the average temperature is cool but not freezing. So if they bury the lines deep enough they get a consistently cool temperature.
Note that deeper pipes probably are the correct answer in places north of Arizona and south of Alaska. But they are the wrong answer for this specific question.
Reddit suggests turning off the heating element in the hot water tank and using the "hot" tap when you want cool water. Then use the "cold" tap when you want hot water. The way this is supposed to work is that the water coming into the house will be hot enough. Whereas the water in the heater tank will cool down to room temperature. You're essentially using your air conditioner to cool the water in the hot water tank.
I haven't tried that (I do not live in Arizona) and it seems suspect. 80°F water is unpleasantly warm if you want cool water but it isn't what I would call hot. And if the incoming water is only 70°F, the room temperature is unlikely to be much lower even with air conditioning. I would consider that warm rather than cool. That said, it still may be better than the way things are now.
The advantage of this option is that you could try it without any new equipment. Turn off the water heater, wait a while (overnight?), and see what happens. You may want to run a bath tub worth of water after you turn it off so as to clear out contaminants (hot water pulls more contamination from the pipes).
If you want water for drinking, consider putting it in a pitcher in the refrigerator. That could also reduce the contaminant problem, particularly if you use filtered water.
I note that your chiller company has a list of supported industries that includes bottling and food processing. So it's possible that they have food-quality options. I would agree though that you probably don't want to use a water chiller designed for welding with your drinking water.
For those in places that don't use Fahrenheit, here's translation to Celsius:
So room temperature with air conditioning will be in the 20-26 range. Although 26 is the government recommended temperature for environmental reasons, 22.5 and lower are common. (I mean that the government recommends not heating above 20 nor cooling below 26.)