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  #1  
Old 02-08-2007, 11:09 PM
bouv bouv is offline
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What could cause cold water pipes to be hot?

The cold water in my house operates extremely oddly. When first turned on, it is room temperature, as one expects it. It then gets warm, and eventually as hot as the hot water...but then a little while later it goes back to being cold and usually stays like that for a while, though sometimes it gets hot again, but never for as long as it was initially hot. The hot water behaves perfectly normally, however, the odd thing is that the cold water, when it gets hot, gets hot faster than the hot water does.

Any ideas? The only thing I cold think of was that one of the cold water pipes is just too close to a hot water pipe/hot water heater and gets warm.
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  #2  
Old 02-08-2007, 11:51 PM
Joey P Joey P is online now
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Like you said, I would assume somewhere it's running to close to a hot water pipe, or maybe even a furnace duct.
A few questions...
Does it happen at all faucets or just one/some?
Does it happen in summer?
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  #3  
Old 02-09-2007, 05:42 AM
Colophon Colophon is offline
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I get the same thing from the cold water tap in my bathroom, especially if the hot tap has been run recently.

It must be because the pipes run close together. If you think about it, it makes sense that the cold would run hot before the hot does, because the hot water pipe is heating up the cold water pipe much closer to the tap (and in the process cooling itself down).

So if you turn on the taps at the same time, you initially get heated-up cold water and cooled-down hot water out of the cold and hot taps respectively. You tend to notice the "hot" cold water more, while the cooled-down "hot" just feels like it hasn't started to come hot yet.
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Old 02-09-2007, 05:58 AM
The Librarian The Librarian is offline
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Quote:
Originally Posted by bouv
The cold water in my house operates extremely oddly. When first turned on, it is room temperature, as one expects it. It then gets warm, and eventually as hot as the hot water...but then a little while later it goes back to being cold and usually stays like that for a while, though sometimes it gets hot again, but never for as long as it was initially hot. The hot water behaves perfectly normally, however, the odd thing is that the cold water, when it gets hot, gets hot faster than the hot water does.

Any ideas? The only thing I cold think of was that one of the cold water pipes is just too close to a hot water pipe/hot water heater and gets warm.
1 Measure the pipe diameter.
2 Measure the amount of water that comes out room temprature.
3 Do the math.
voilá
The location of your mysterious heat source.

Have you considered turning your boiler of and be content with FREE hot water.
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  #5  
Old 02-09-2007, 07:42 AM
Harmonious Discord Harmonious Discord is offline
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It sounds like water from the heater is back flowing into the cold water pipe. The water in a water heater expands and the pressure causes the hot water out of the tank. You may want to look at a one way valve and an expansion tank to prevent this. Your system may become too pressurized when you limit the area of expansion, if you don't add in the expansion tank. You may find the heater or pipes have burst, if you only install the one way flow valve.

I was at a state park. We were covered with dust and the showers only trickled water. Ny brother used the shower first. I got a drink outside and the bubbler was dispensing hot scalding water. The hot water tank emptied out and I could drink it. By that time the showers were cold, because all the hot water went out the bubbler.
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Old 02-09-2007, 08:48 AM
zut zut is offline
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Quote:
Originally Posted by bouv
Any ideas? The only thing I cold think of was that one of the cold water pipes is just too close to a hot water pipe/hot water heater and gets warm.
Likely that. Although Joey P's questions are germane.

In our bathroom, the pipes to the sink run alongside the steam heat pipe for some length. Apparently the cold pipe is closest, because the "cold" water can get quite warm.

The sink is against an outside wall, so that the pipes *also* have to pass quite close to the outside of the house. On very cold days (like we had earlier this week) the water in this section of the pipes can get pretty cold. In addition, the heat's likely to be on longer and more often, so the pipes neas the steam line can get pretty hot.

That leads to an interesting situation, which has happened to me occasionally: My wife will get a drink of water or whatever using the cold water from the sink, effectively "staggering" the hot and cold water lines. I'll follow right behind, and turn on the cold water tap: the "cold" water will get hotter and hotter as the slug of wamed water pours out. That freaks me out, so I shut it off and turn on the hot water tap: the water from this tap will get colder and colder as the slug of water that's in the exterior wall pours out.

Took me a while to figure out what the Hell was going on.
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  #7  
Old 02-09-2007, 11:55 AM
AskNott AskNott is offline
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I saw a This Old House ep that dealt with this phenomenon. The homeowner's water heater would leak a little from the t&p safety valve, maybe a few gallons a week. The problem is that the heater builds up pressure from the heating, and it has to go somewhere. The cure was a pressure expansion tank next to the heater to give the expanding water a place to go.

In the past, this expanding water would go into either the inlet pipe, back toward the meter, or into the house's cold water pipes. Many new houses, though, have check valves to prevent this backflow. In your house, you might have a stuck check valve between cold and hot. With greater pressure in the hot side, the flush of a toilet can draw hot water into the cold side. It can be alarming to sit down over a toilet full of hot water.
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  #8  
Old 02-09-2007, 01:04 PM
solkoe solkoe is offline
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My mother has this. Her water pipes run inside a heat duct. This is because the bathroom is a reno on the top floor and placing the pipes in the duct was the best way to travel through the height of the house.
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  #9  
Old 02-09-2007, 05:06 PM
ThomasHanks ThomasHanks is offline
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hot water would make them hot.
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  #10  
Old 02-09-2007, 07:44 PM
bouv bouv is offline
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Thanks for the answers, I figured it had to be something simple. And it's been doing this on most, if not all, the cold water lines in the house since we moved in in August, so it must be close to the hot water line or water heater, and not just a furnace line.
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  #11  
Old 02-09-2007, 10:12 PM
Autolycus Autolycus is offline
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A 1920's style death ray could heat up could water pipes very nicely I reckon.

Oh wait, you meant what is likely to be heating them up? In that case, I have no clue. Some of the responses above me had good suggestions though.
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  #12  
Old 02-10-2007, 09:53 AM
SpectBrain SpectBrain is offline
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We noticed this in our house when we first moved in. Turned out that the clever previous owner had decided he didn't want to wash his cars with cold water and so he brought a cold and a hot water pipe together in a 'Y' configuration. The hot pipe and the cold pipe each had a valve and the mixed water went to a spigot. If the hot and cold valves were left open hot water would go back into the cold water line and we would get very warm water from the other cold water faucets in our house. One way valves in the arms of the 'Y' fixed that.
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  #13  
Old 02-10-2007, 10:24 AM
According to Pliny According to Pliny is offline
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When pipes touch they will transfer heat between them.
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