Cold water inlet temperature

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<<Here in suburban Chicagoland,
I love that term - I watch a lot of WGN reruns on cable so I always end up watching the "Chicagoland" news inadvertently. The first time I heard the term, I thought they were talking about some sort of amusement park.
<< there is almost always a rash of municipal water main breaks after a good cold snap, due to the water mains shrinking due to the scold temperatures that get down to the level of the installed pipes.>>
That was another question I had - how long does it take to "cold soak" the ground. I've read alot about freeze lines but these pipe ruptures seem to be occurring well below that level.
<< Unless there are some strain reliefs periodically, the shrinkage causes stresses and the weakest one breaks. Stress relief usually takes the form of an "S" bend periodically.>>
I don't know whether it's still true, but I recall seeing on TV that some municipal water systems are so old they are still using wooden mains. I guess I should ask Google.
<<CHELAN, Wash. - It has been 2,000 years since the Romans built their aqueducts, and 200 years since Philadelphia began using cast-iron water mains. But the 6-inch-wide city pipe that still delivers drinking water to a block on Nixon Street here uses an even more primitive technology: wood. . . . Water officials say they believe that a handful of wooden water mains are still in use in South Dakota, Alaska and Pennsylvania, among other places. The old wood pipes offer a vivid reminder of the age and fragility of the nation's drinking water systems, many of which rely heavily on old pipes that often remain out of sight and mind - until they burst.
And they are bursting with alarming frequency in many areas these days, particularly in systems coping with septuagenarian, octogenarian, and even century-old pipes. There are an estimated 240,000 water main breaks each year in the United States, according to the Environmental Protection Agency' s Aging Water Infrastructure Research Program, and some water experts fear that the problem is getting worse. >> Source:
http://www.nytimes.com/2009/04/18/us/18water.html
When the water main on my street broke last week, the water people had a prerecorded message on their emergency number saying they were working on several large breaks in the area. So it does seem to follow the cold weather. Repairing broken mains can't be fun to do when it's 15F and windy out.
It turns out that a lot of "schmutz" got into the water pipes. I spent some time today clearing out some nasty looking debris from the screens in the bathroom and kitchen faucets. It seems the showerhead got hit, too. )-: Probably time to consider a whole-house water filter. When I first moved in, I found an acorn lodged in the kitchen faucet.
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Bobby G.



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If the water heater has to operate longer to bring the incoming water up to temperature translates into " increased stress", then so be it. But that's how it is supposed to work. MLD
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If NASA had a little foresight about the problems of cold weather, they might not have dropped the Challenger into the ocean. If the USN had realized what happens to ballast blow valves (as they were designed before 1963) at depth (they froze solid) the Thresher might not have sunk.
What I am concerned about is limiting the delta between the incoming very cold water and the much warmer tank interior. There are several ways to go about that.
I've already taken one step, which is to reduce the incoming pressure to the whole house. That slows down the amount of water that can enter the water heater and reduces the potential thermal stress.
I'm also going to turn the water heater's thermostat down just to lower the over all temperature differential. The cooler the WH output, the lower the delta between incoming and outgoing water.
A third action is to trim the hot water feed valve to the washing machine so that it doesn't draw anywhere near the GPM of a wide open valve. It will take longer to fill (will be measuring that as we do laundry) but it's not a very big thing to wait an hour instead of 30 minutes for the laundry to be done. It's not like I am outside in the bitter cold beating the clothes on river rocks. (-:
A fourth action will be to avoid the HOT only wash cycle during bitter cold months (we typically wash our LBL dog's blanket in hot water), thus further slowing down the amount of cold water that's introduced into the tank quickly and lowering the thermal "shock" to the heater.
If I wanted to spend money, I might look into a pre or post water heater expansion tank or put aluminum fins on the pipe leading from the master intake to the water heater. That's at least 25' feet of copper pipe that could transfer some room heat into the incoming water, but I think that's way overkill.
I think reducing the pressure and the temperature while taking care not to draw enormous amounts of hot water will substantially reduce the thermal differential and the risk of catastrophic failure from thermal stress. It will be just my luck that it fails as a result of crud getting into the lines from the recent water main break, but at least I will have tried. (-:
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Bobby G.




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That would limit the rate but would have no effect upon ther amount. ___________________

It also means that the hot water temperature will be lower which means you'll need a greater amount of it to get the same temperature fom a mixing valve faucet. ___________________

I think you are busy making mountains out of mole hills :)
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dadiOH
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Robert Green;3195907 Wrote: > I am wondering if prolonged cold spells substantially reduce the > temperature of the water entering a house from the city water service . > . .
They definitely do.
Winnipeg gets it's water from Shoal Lake, which is a lake in the Whiteshell Provincial Park about 60 miles from Winnipeg.
If you have a single lever shower faucet, just take note of what the faucet handle position is in summer and in winter. The hot water in your water heater will be the same temperature (or close to) year round, so that the difference in handle positions is entirely due to the warmer cold water in summer and colder cold water in winter.
Water main breaks aren't caused by the pipe shortening due to thermal contraction in the cold. Normally, in winter, the ground freezes to a certain depth which we call the "frost line". Water supply pipes and sewer lines will be buried well below that frost line so that the water in the pipes doesn't freeze. But, what happens is that as moisture in the ground freezes and expands AT the depth of the frost line, ice "lenses" form. They are called ice lenses because of their shape; being thickest in the middle and thinnest at the edges. These ice lenses are very localized, typically being no more than about 100 feet in diameter. It's the downward pressure exerted by the water as it freezes to the bottom of the ice lens and expands that causes water pipes to break underground. The force of water expanding as it freezes is pushing down on the pipe one place, and as little as 30 or 40 feet away, you don't have that pressure, and so the pipe bends until it breaks.
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nestork


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nestork wrote:

Hi, Here in Calgary, most house has water pressure gauge set at 60 psi when water is running. Winter/summer, no difference. Our pipes are minimum 6 feet below ground. Is some one paranoia of something? Water heater is designed to work normal under normal conditions. I wouldn't worry and fiddle with it. If some one wants to experiment to prove some thing, it'll take at least for the life of water tank with every thing observed/measured documented. Also water main butrssting in cold weather is due to rather from the ground heaving than freezing water causing water lens.
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It depends upon where you live and the source of the city water.
If you live somewhere that has wide swings of temperature from season to season the water temperature will also vary and the anount of variation would change with ground water depth. If the source is surface water as opposed to ground water it will vary even more. FWIW, the water in Honolulu (ground water) varies about 2 degrees between winter and summer.
I would think that temperature variation also depends upon how the water is stored, transmitted and the overall rate of use. For example, if you live somewhere that uses ground water but provides a head to it via elevated storage tanks, the ground water temperature is going to change in the storage tank, colder in the winter, warmer in the summer; however; if the water in the tank is being used and replenished rapidly, that variation would be minimized.
I get my water (central Florida) from my well which is about 110'. At the moment, I set my single handle shower mixer at about 10:30; come August, it will be at 1:30 so there is considerable temperature variation in the source, no idea how much in degrees.
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dadiOH
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On Mon, 10 Feb 2014 11:40:30 -0500, "Robert Green"

I'm sure. The water coming from the cold water faucet is colder in the winter than in the summer. And I've noticed it's even colder this winter.

People often use "stress" or "strain" to talk about machines. I think it rarely applies. The water heater elements are on more if the input water is colder. If the elements are going to wear out, they wear out that much sooner.

Sounds about right.
You can put the thermomenter in a short glass of water and watch the temperature as the running water replaces the water in the glass and see how long it takes until the temp stops dropping. (I know, ony part of the overflow is old water, but you can figure it out.)

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wrote:

temperature

I disagree. Dad was a materials science engineer for the Navy and spent lots of time deliberately stressing equipment to determine its failure point. Thermal stress testing is an integral part of manufacturing. Virtually every device I know of has specified high and low temperatures of operation listed in the manual. That's because so many things behave differently in the extreme cold (plastic gets brittle, batteries fail) or heat (plastic becomes soft and batteries boil over) than they do at normal room temperatures.
http://www.google.com/search?q=thermal+stress
Will give you some idea how much study is devoted to the topic. It's a whole separate branch of mechanical engineering AND materials science.
Water heater tanks expand and contract as the internal temperature changes and each expansion causes a slight degree of fatigue on the metal. The greater the difference between the tank interior temperature and the inlet water temperature, the greater the stress on the materials involved. Put on some goggles. Go take a plain glass bottle, fill it with boiling water and plunge it into 41F water. That concludes today's demonstration of thermal stress. (-:
Am I being overly cautious? Maybe. But with a water main breaking on the street in the same week my neighbor's water heater failed, I've got a right to be a little worried.

And that temperature difference results in increased mechanical stress on the elements as well because they are contracting and expanding more than then do with warmer inlet water. It's not just the number of extra cycles, it's the exposure to far greater cold than usual. The greater the delta, the more mechanical stress on the elements and every other component of the heater.

That's true, of course but the current weather conditions are subjecting an old tank (it's 18 years old) to stress levels not seen during its long service life. I'm perfectly comfortable with the assumption it needs to be replaced soon. But I want that to be in the warmer weather. Changing it out right now would be drastic, expensive and foolish because it's impossible to get a bargain from a plumber on parts or labor because the current demand is nearly insatiable. My neighbor had to call 10 places to find one that one do it the NEXT day and even they lied to him. It took two days.
I've got a working water heater now showing no signs of distress other than the noises it was making when I initiated a 20G fill of all hot water for the washing machine. I considered that a clue that it might be a good idea to throttle back the heat setting and the water pressure for now to reduce how drastic the change of temperature is within the tank.
It's taken hours to explain it but less than a minute to do. Despite the assurances I'm wasting my time, very little of it was actually consumed and no one, except Vic, has provided a reason (possible valve failure) why someone shouldn't reduce the temperature setting and trim the inlet flow until the weather and the inlet water temperature warms up.
Despite the surprising amount of resistance I've been reading, I am sure at least one person's already either turned down the heat or the water flow - just to be on the safe side. (-:
FWIW, just a few degrees outside of normal operating range can have drastic consequences:
<<Constance Tipper of Cambridge University demonstrated that the fractures were not initiated by welding, but instead by the grade of steel used, which suffered from embrittlement. She discovered that the ships in the North Atlantic were exposed to temperatures that could fall below a critical point when the mechanism of failure changed from ductile to brittle, and thus the hull could fracture rather easily.>>
http://en.wikipedia.org/wiki/Liberty_ship
The SSN Thresher was also the victim of the cold, but in a more obtuse way:
<<When the high pressure air that was used to blow the tanks left the storage banks, it passes through the control valves that keep it in the banks under pressure. Anytime a compressed gas expands, it cools rapidly. As the very cold air passed through the valves, frost began to form due to the presence of moisture in the air. It very quickly built up (a matter of a few seconds) and froze solid in the valves. The solid ice stopped the air just as effectively as shutting the valves, thus the Thresher was unable to blow her tanks.>>
http://www.navsource.org/archives/08/08593b.htm
I would never underestimate the effects of extreme heat and cold on mechanical systems. Hell, I drove a Jag MarkX that had a terrible tendency to overheat in warm weather and the only way to stop it was to shut off the A/C, pop up the bonnet air scoop and run the heater full blast. That was usually in the middle of the hottest days in the summer. It's been my experience that cars designed outside the US don't quite operate as they should in the climate extremes of the US. It took a long time for the Japanese to understand the need for Desert Valley cooling capacity in passenger cars.
Of course, when you consider the VW Bug's absymal heating system, it might be true that some cars just didn't operate as they should *anywhere* regardless of climate. You would think with all that snow and cold, they should have built a working heater.
Speaking of snow and cold, it's 2AM in DC and it's snowing like a mother.
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Bobby G.


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pressure tanks are installed to protect water heaters and prevent pressure release valves opening when water mains have a check valve so water from sa y a swimming pool being filled cant siphon back in the mains and add contam inated water to the main in case of a water main break......
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<pressure tanks are installed to protect water heaters and prevent pressure release valves opening when water mains have a check valve so water from say a swimming pool being filled cant siphon back in the mains and add contaminated water to the main in case of a water main break......>
But I don't have a swimming pool! And I obviously don't have a check valve on the water line coming into the house because the recent water main break completely drained the house water lines. That wouldn't have happened with a check valve in place.
I expect I'll have to call the county inspector to find out why the expansion tanks are now required by code.
--
Bobby G.




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wrote:

Yep. But they don't have them in my location.
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I do beleve in common sense actions to protect homes.
but all this effort to protect a old water heater might be over kill...
if its that old its probably best to just replace it before failure.
of course I tend to replace car batteries befor they leave me stranded, and old water heaters before they leak......
in both cases its better to replace when cnvenient for me, rater than waiting for a big leak or getting stranded when in zero weater a vehicle wouldnt start..
incidently I discovered replacing car batteries at 4 years old helps prevent alternator failures.
but one can spend so much time and effort trying to get the longest life out of everything its just not worth the effort..
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news:bcf69c22-bade-4705-b6e1-

"All this effort?" I turned the main shut off valve less than half a turn. Then I turned the water heater temp control less than 30 degrees. Why do people assume there's all this effort involved? I have to wonder.
I didn't have to eat my sled dogs or ponies on the perilous journey to the basement because I ran out of food like Captain Scott:
http://www.rmg.co.uk/explore/sea-and-ships/facts/explorers-and-leaders/scott
Cutting back on both the operating temperature and overall water pressure took all of one minute. Jeez. Where's all the effort some people seem to believe is involved in trying to protect an old water heater from some very unusual weather conditions? To me it's just elementary to try to compensate for conditions that the water heater has never before faced over its entire service life and will never likely face again.
Just remember how many people in authority poo-pooed the engineers that recommended that Challenger's flight be postponed until the very rare cold snap had ended. Extreme cold weather has consequences. In NASA's case, fatal ones.
Trying to reduce the effect the extreme cold might have on an old water heater seems to me to be simply prudent behavior, especially since the steps I took were so damn easy. Twisting a valve and a dial both less than 1/2 a turn. What is it that Trader says?
"Good grief!" (-:
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Bobby G.



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wrote:

I wait until a tank breaks. The tank will just leak down into the floor drain. A bad battery shows up in the winter. Slow crank. Last one I bought lasted at least 6 years. Car broke down first, then my son put it in his car. Water heater was here when I bought the house, then it lasted 15 more years. I have put in a couple alternators, but don't think it was battery-related. Batteries tested okay. GM cars don't have long lasting alts.
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