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First off, I live in Phoenix, AZ. This is desert here. I live in an area where people mostly have natural desert landscaping rather than lawns.

Now, this will sound really odd to folks who live elsewhere, but the house I'm in now does not get "cold" water in the summer. I can literally shut off my hot water heater and take a shower just from the cold water coming in from the city water line. The so-called "cold" water temp is somewhere over 110 for most of the summer. It's fine for most of the rest of the year, just not from May thru Sept.

I've lived in different parts of the city throughout my life, and this is the hottest "cold" water I've ever had to deal with. I think a big part of it is because the ground in this area is quite rocky and sandy, not much solid dirt. And it's dry as a bone.

Where you've got a water main running under yards that have lawns that are watered regularly, the water seeps into the ground and cools the ground and whatever pipes are there. Hardly anybody in this area has lawns, certainly nobody along the route where my water main comes from.

Short of putting a 50 gallon water cooler into a fridge (the opposite of a water heater), I'm wondering if anybody has any ideas about how I might rig up something that could cool the water coming into the house by 20-30 degrees?

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UPDATED 12/10/22

So I forgot about this post and just stumbled upon it again, although I haven't solved the problem yet. It's now winter in Phoenix, so I need some hot water mixed into the cold so it's comfortable. We actually get cold water from the tap from Sep thru May!

Most of the replies seem to be from people who think what I'm saying is as unbelievable as you telling me that you have to worry about water pipes in your walls freezing up. A "freeze" warning here means we have to put sheets over some of our shrubbery for the night. Nobody's pipes freeze here. Are you sure you don't have a refrigerant leak in your A/C somewhere? Trust me, the "cold" tap water from the city has been measured at 112º at times in my area. And the outdoor temps really do get as high as 125º here in the summer!

Anyway, I've come up with this working idea and I'm curious what sort of mechanical ideas you can think of. (I'm a software geek, not much good with this kind of thing.) If I'd be better off making a new post for this, let me know.

I'm thinking of getting something like this from Amazon or Home Depot: Rain Bird T63-500S Drip Irrigation 1/2" (0.634" OD) Blank Distribution Tubing, 500'

By my calculations, a coil of that should hold about 8 gallons of water that would weigh 67 lbs. If I were to build some kind of frame to simply expose it to the air, perhaps hanging from the ceiling above the tub, it would settle to an ambient temp of around 85º. I use a 1 GPM shower head. Using a splitter that can let me send some of the water coming to the shower head into this coil, then mixing it back into the original water flow, could reduce the temp to around 95 degrees for at least 10 minutes, which is about how long it takes me to shower. Worst case, I'd get 8 minutes of a nice cool 85º shower before it went back to "almost scalding hot". :)

What's the best way to suspend 500' of tubing like this from the ceiling with enough space between the coils to allow air to flow? The space is above a normal sized porcelain over metal tub. Would you just hang it from the ceiling joists? or maybe put some metal poles in the corners to support it? I'd be worried about it sagging in the middle or just falling down. In the cooler months, I can drain it since it's not needed.

Also, the tub is on the most exterior part of the wall, and there's no crawl space above it in the attic. So getting up there to do anything is a non-starter short of tearing the roof off.

NOTE: this is not a problem unique to my house or my street. Most restaurants and commercial properties that do not run their cold water lines through their chiller system will have "cold" tap water that's between 95 and 100 degrees. I don't know where folks think it's supposed to get cooled down when the ambient temps outside are well over 100, the ground is mostly covered by cement, asphalt, and bricks/blocks, and underneath is colichi, sand, and clay. We get rain during the monsoon from early July thru Sept, and it's mostly at night. It does not soak into the ground, but mostly runs off. After a rare afternoon rain storm, the ground is dry in an hour.

It's clear that most people who don't live here cannot comprehend water coming out of the "cold" water tap at nearly 100 degrees. I cannot comprehend how anybody lived here before A/C was invented!

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  • How much cooled water do you need to have available? How quickly does it need to replenish itself? (Think about recover time of hot water heaters—you use too much and have to wait for more) It seems like most in-home uses for colder water involve drinking (and brushing teeth). Just thinking about this, I personally turn on the hot far more often than the cold.
    – Tyson
    May 6, 2018 at 10:51
  • Well, it's just plain annoying not being able to get "room temperature" water out of the tap. If it's a hot day and you want to splash some cool water on your face, or put some cool water on a washcloth to wipe your face or take off a layer of sweat, or just jump in the shower to cool down, you can't! I don't like "cold showers" but when it's 110+ outside, "room temperature" water is quite refreshing. Water coming out of the fridge at 38 degrees would require hot water to warm it up. But if the water out of the tap was even 80 degrees, it would be nice.
    – DPS
    May 6, 2018 at 17:07
  • 1
    Are you sure that you do not have a cross-over problem? Do you have any older single handle Moen Faucets in the house? If you do replace all the cartridges. This may be the issue.
    – Paul Logan
    May 6, 2018 at 17:41
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    Also just remembered another item that’s horrible for creating crossover, awhile back (15 years) in our area there was a plumbing company actively pushing (selling) hot water recirculation systems that didn’t require a return. Instead they put a valve under the sink to use cold pipe. The valve was thermal actuated and was supposed to close when it got hot.... those valves failed A LOT however, leaving both hot and cold hot everywhere even the toilet. Also can you ask your next door neighbor if they have a hot city water problem?
    – Tyson
    May 6, 2018 at 18:50
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    As I said, the cold water temp is fine until the outside temp starts pushing 100, as it is right now. If there was a crossover problem, it would happen year-round, right? And I don't have any kind of recirculation. I kept the hot water heater on its lowest setting all last summer, and the gas bill was ridiculously low.
    – DPS
    May 7, 2018 at 3:27

9 Answers 9

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Very common in tropical Australia, not a big deal. The ground gets hot in summer and even though the street pipes are six feet underground the water can scald. Every summer we turn off the power to the hot water storage tank, it then becomes the cold water supply. If we use too much "cold" water the tank warms up. The house has an evaporative cooler and the tank is positioned inside the house and is cooled.

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    This technique could be enhanced with a very basic flat plate solar water heater -- if water is pumped through that heater at night it becomes a night sky radiant cooler instead!
    – Greg Hill
    Jul 31, 2019 at 20:47
  • @Stephen can you explain a bit more? You're saying the water heater becomes the cooler?
    – Johnnytest
    Dec 28, 2022 at 7:21
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I have lived in Phoenix since 2006.

Here's a solution I found:

  • Get a large metal colander
  • Get a rubber/plastic bowl about half the size of the colander then freeze water in that bowl
  • Find a way to hang the colander under the shower head
  • Place the chunk of ice in the colander and let the shower water run over the ice and sprinkle through the colander down on you.

It actually works!

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Are you sure the water is really heating up in the ground outside your house? In my house (in interior southern CA where it is regularly over 100 in the summer/fall) we also have a problem with hot "cold" water, however I discovered while working on another project that the source was the plumbing inside the house.

It seems that the builder/plumber home-ran all the plumbing in the house to two huge manifolds in the garage attic space, complete with a ridiculous ~60 foot service loop in the 1.25" feeder pipe for what reason I am not certain. That created a massive amount of water just sitting there sucking heat up from that hot attic space all day.

A combination of cutting out the extra pipe, insulating the leftover, and insulating the attic space reduced the temperature of the "cold" water by over 30 degrees F in our case.

You might snoop around your service plumbing and see if you have a similar situation.

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  • It gets up to 150º in the attic in the summer. There's 2' of blown-in insulation, and probably lots of scorpions living up there. You're welcome to come poke around and see what you can find. But the tap water inside is pretty much the same temp as coming from the spigot where the city water feed comes into the house.
    – DPS
    Dec 10, 2022 at 8:49
  • Phoenix gets its 'drinking' water from a man-made reservoir that's feed by an uncovered aqueduct traveling though and ending up in the desert. So yeah. Your water travels underground for a lot of it, and I'm guessing it doesn't come out brown.
    – Mazura
    Dec 12, 2022 at 21:35
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  1. Exclude a crossover problem in the shower valve as described by @Paul Logan above. Test the temperature of the incoming city water say at an outside faucet.

  2. If the incoming city water really is 110 F, then make your own cool water (say 80 F) by the batch by putting enough ice into a bucket with 1 or 2 gal of water. Take a quick shower using a low flow shower head say 1 gal/min using the house (hot) cold water to get clean (less volume of water means less heating by the water). Then as a final cooling rinse repeatedly dip a small bowl into the cool water and pour it over yourself.

  3. Alternatively, get a camping shower and pour the ice cooled water into the reservoir and spray it over yourself as a final rinse.

  4. Get one of the old fashioned canvas water bags and hang it outside in the shade. Evaporation of water seeping through the canvas will cool the remaining water inside. Use that for the final cooling rinse.

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  • 1
    Why would using an outdoor faucet eliminate crossover caused by a faulty valve? I would think to test for crossover in a faulty single handle cartridge the feed from or to the hot water heater would have to be closed off.
    – Tyson
    May 6, 2018 at 18:43
  • I just thought that was a simple test which might be diagnostic if the problem was the crossover in the shower valve itself, and hot was only leaking over to the cold when the shower valve was on. (In some plumbing systems the take off for the outside faucets is before the takeoff to the water heater.) One other possibility is that there might be a faulty thermostatic mixing valve on the output of the hot water tank which is allowing hot water to get into the cold water supply. but I doubt this house would have that. May 6, 2018 at 20:52
  • Hey, hey, I like the creativity! Look, it's not just the shower. The bathroom sinks and the kitchen sink have the same issue. And I have no single-handle valves anywhere. If I let the cold water run long enough, the stuff that was in the walls and attic get flushed out and I start getting the water that was in the pipes in the ground outside and finally from the water main. It's HOT. Uncomfortably so when it's over 115 outside. That's all there is to it.
    – DPS
    May 7, 2018 at 3:31
  • So are you doing anything right now to get a more cooling shower experience? What kind of shower head do you have? May 7, 2018 at 8:54
  • I'm not doing anything other than not using hot water b/c the "cold" water is plenty warm enough. It's just that it literally gets "too hot" at times during the summer. That's why I posted this, to see if anybody has any ideas about how to cool it down.
    – DPS
    May 7, 2018 at 19:59
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Is there any practicality of digging your own well to bring up water from deep in the ground? If you could do that then the water temperature would be closer to the average deep crust temperature of the earth.

Digging a well in most areas is probably limited to folks that have a certain minimum size of property. There are also many other local restrictions as well.

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  • This house is elevated above the valley floor due to its location at the foot of a peak that tips 1500', and I suspect the depth to a water table might be quite a bit. But it's something to consider. (Everybody in this area has city water, AFAIK, but we have no sewer; we're all on septic tanks, if that says anything.)
    – DPS
    May 6, 2018 at 17:15
  • No wells exist in this immediate area from what I've been told. Not practical. Early settlers, and indeed the natives who were here hundreds of years before the Spaniards invaded the region, brought water in via canals leading from a couple of rivers fed from the mountains around the valley. We still rely on them for a large amount of our water needs.
    – DPS
    Dec 10, 2022 at 9:01
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Perform a search for "undersink water chiller". You will find products in the $ 200 - $ 600 range retailed by companies like Amazon and Home Depot, capable of chilling about a gallon of water per hour, and capable of storing 2 - 3 quarts of chilled water.

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    How much water would I need to cool down 10 gallons of water over 10 minutes from 110º to 95º or so? I don't think a few quarts is going to go very far. Maybe for washing my face. I think some ice cubes in the sink would be a lot cheaper. :)
    – DPS
    Dec 10, 2022 at 8:51
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This is just an idea, I guess it would be a variant on another answer suggesting you use the hot water tank for cold water supply part of the year.

Most well systems use a pressure tank in the basement of the home, the well pump fills the pressure tank from the hole in the ground, and the tank supplies the water in the house.

You could install a pressure tank that's simply fed from the water company supply, and in turn supplies the cold water for the house. (You could bypass the pressure tank to supply the water heater.) The pressure tank would serve as a simple cistern or reservoir where the water cools to your basement's ambient temperature. I believe it would cool faster than the water heater tank because it's uninsulated, and you could leave it in place year round. This should not be that difficult of a plumbing job.

You could even conceivably bury the tank in your yard or in your basement floor for better cooling. I am pretty sure that 4' underground the temperature is pretty cool, but you could easily core drill a small hole down a few feet and run a temperature probe to see before you did all that work.

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  • I'm located on the downslope of a "mountain" that a neighbor said was built by adding dirt above the bedrock. It's not very far down.
    – DPS
    Sep 6, 2020 at 19:46
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Second hot water heater, used just for its reservoir.

If your hot water heater is not on and you try to get hot water, you get cold water. In my house, hot water comes from the hot water heater off the garage which keeps a tankful hot for when we want it. Cold water bypasses the hot water heater.

Get a second hot water heater. Have it installed with your cold water line as though it would be a hot water line. Don't attach the new hot water heater to the gas. Now you have a reservoir that will cool its water to your ambient basement temperature. Maybe you could even acquire a dead hot water heater and use it just for the reservoir - but not one full of mineral deposits.

I propose a hot water heater not being used for heating because I am not sure about all the internal stuff that lets these things regulate water flow. Hot water heaters have all that internal stuff and that stuff all still works when the heater dies and the water is cold.


It occurs to me you could do a test run of this idea by turning off the hot water heater you have now and letting the tank cool down. Your "cold" water would stay 110F but if this idea has merit your "hot" water should be ambient basement temps.

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  • Wouldn't the insulation in the water heater tend to keep the hot water hot (as opposed to a tank)?
    – RetiredATC
    Jul 24, 2022 at 1:29
  • @RetiredATC - I imagine it would. I have never seen a plain tank for this sort of use. Maybe they exist. OP can still test out existing heater for this use without much trouble. I have to think that it will cool off some overnight.
    – Willk
    Jul 24, 2022 at 1:40
  • Sorry, that doesn't work either. I can turn off the hot water heater completely and take a shower and it's still too hot. A second one would be the same temperature. What's going to cool either of them down in the summer? THAT is the problem I'm trying to solve.
    – DPS
    Dec 10, 2022 at 8:56
  • @DPS - winter now and hard to test. My suspicion is the line into your house is outdoors somewhere and so water inside gets to ambient outside temp. If in summer you have hot water heater turned off and then take a "hot" shower (the shower takes water mostly from the now-cold hot water tank) is that still hot?
    – Willk
    Dec 10, 2022 at 19:45
  • This is not unique to my house, my neighborhood, or even my part of town. Most people who visit Phoenix stay in hotels, and the builders had to run their cold water lines through the chiller to provide cool water at the taps. The cheap motels don't do that, and the "cold" tap water is close to 100. Same for most restaurants, bars, gas stations, coffee places (even a lot of Starbucks). I have a fitness place I go and there's hardly any temp diff between hot and cold water, which I really hate because I like a cool shower after working out.
    – DPS
    Dec 11, 2022 at 23:22
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I'm thinking of getting something like this from Amazon or Home Depot: Rain Bird T63-500S Drip Irrigation 1/2" (0.634" OD) Blank Distribution Tubing, 500'

OK

To get 4 liters/min (about 1 gallon) through 500ft of that pipe, assuming internal diameter of 8mm, you'll get a pressure drop of 4.5 bar (66 PSI), which is a showstopper.

If internal diameter is 10mm, that's 1.6 bar, or 23 PSI, which should be okay. So I'll assume 10mm ID from now on.

You can hang the pipe as a coil on a pole suspended from the ceiling.

500ft (150m) of 10mm ID pipe contains about 12 liters so we're quite off from 8 gallons, maybe you need a thicker pipe.

However once you have taken your shower and the pipe is filled with hot water (say 45-50°C) two things will happen:

Above about 50°C PEX pipes become much softer, so the whole coil hanging is probably going to sag quite a lot. That could make a handy gauge for how much cold water is left! I'm absolutely sure 20mm OD PEX pipe will not kink from this, but I'm not sure about the flimsy gardening pipe.

Then the huge surface area of the pipe will make an excellent heat exchanger with the ambient air in the bathroom. Given the water volume, the whole bathroom will heat to the temperature of the incoming "cold" water. So right after your shower, you'll have to towel yourself outside of the bathroom, otherwise you'll sweat buckets immediately. Then the bathroom will essentially become a steam cooker until the AC sucks out the heat, which could take a while.

I have actually experimented with this stuff: when we were laying the PEX pipe for the underfloor heating, we had to run hot water through it so it would soften and bend properly. So, with 20-30m of pipe lying on the floor and 55°C water, turning on the hot water tap, the whole room heated extremely quickly. And you're planning for a lot more pipe!

So I'm not sure it would be entirely practical (not mentioning the modern art sculpture hanging from the bathroom ceiling).

Personally I'd get a solar water heater, the kind of tank with an extra coil inside to circulate hot water from the solar panels. You can even use it in the winter to get hot water, assuming you get a lot of sun. The idea is to use a small circulator to pump water through the internal coil, then run this water through a heat exchanger placed in the AC duct... maybe a hydronic blower heater, or just a coil of pipe. So it would cool the tank slowly, over the whole day.

If you get cold nights in the desert, another solution would be to just put the large pipe coil outside, and use a circulator at night to cool the whole water tank.

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  • 1/2" is 12.7mm -- that's the inside diameter (ID) of this tubing. Calculations I've found say 500 feet of 1/2" tubing holds just shy of 8 gallons of water. The bathroom itself is rather small. There's an exhaust fan, and in the summer the mirrors don't even fog up, like they do in the winter. There's an A/C vent that blows cool air into the room in the summer, which may be why. I could put the coils into a larger container that's filled with water to act as a temperature mediator. The cooler A/C air would slowly cool it all down and make it useful for once-a-day use.
    – DPS
    Dec 11, 2022 at 23:07
  • Yes putting the coils in a barrel full of water seems like a good idea to avoid the "instant space heater" effect
    – bobflux
    Dec 11, 2022 at 23:31

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