Strange hot water question

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Darter1585

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Went on a long trip in our 2015 Thor Siesta 24ST.  A couple of times when I was unhooking the city water connection at the coach, I noticed that the water coming out of the connection was hot.  I leave the water heater on 110v when I have shore power, so the water is always hot.  I checked to make sure the valves were in the correct position.  Does anyone have a theory on this?
 

Rene T

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I would think that if the water inlet where you hook up your hose was real close to the water heater, the heat from the tank could transfer out the cold water line a little. In a older RV I had, the kitchen sink was right over the water heater. Every time I opened the cold water faucet, I would get a short burst of warm water. 
 

John From Detroit

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FIrst you should not have water coming OUT of the city connection other than a few drops.  There is a check valve that is part of the connection assembly.

Second;.... One Sunday (or THursday not sure which) in GA I forgot I had the water heater turned off. I still  had a nice warm shower... Power of the sun on the fresh water hose had heated the water to a nice shower level. No need for Electric or Propane.. Yes it was August.
 

Gary RV_Wizard

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My thought is the same as John's: Why did any water come out of the city inlet? It has a check valve that closes it off completely as soon as the external pressure is relieved (hose unscrewed somewhat).  If the hot water you feel is coming just as the hose is loosened, it is coming from the hose, not the RV plumbing.  The water in the hose gets quite warm with any sun at all - it doesn't even have to be a hot day.
 

Darter1585

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Thanks for all the input.  The city water connection IS very close to the water heater, and it?s also directly below the furnace.  I can?t remember if this happened on a day when the furnace had been running ( we had snow in Yellowstone at the end of August). In any case, I don?t think it?s anything I?ll be terribly concerned about :)
 

Rene T

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Darter1585 said:
Thanks for all the input.  The city water connection IS very close to the water heater, and it?s also directly below the furnace.  I can?t remember if this happened on a day when the furnace had been running ( we had snow in Yellowstone at the end of August). In any case, I don?t think it?s anything I?ll be terribly concerned about :)

Did you notice hot water on the day it snowed when you disconnected?  If it was cold, that would possibly rule out the sun heating the water in the hose.
If you are still concerned, you could always put a check valve in the inlet line to the water heater that's if the water is being heated by convection.
 

John From Detroit

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Water is unique in that when it freezes it expands. but all things expand when heated as well.  So when you take water at say 60 degrees from the well and heat it to 120.. Well been a long time since I did the math but you convert both temps to Kelvin and that predicts the amount of "Swelling" due to heat. from that there is a whole bunch more math that predicts the increase in pressure. Well it "Backs up" in the pipes a bit. if water leaks out before the check valve closes.. Hot is a posibility.

THis is part of the reason RV Showers tend to give you a blast of either cold or hot when you restore flow after cutting it off with the head valve.
 

FunSteak

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We had some water leaking from the tank fill port when we got our coach.  Turns out it was simply the little screen inside, attached to the rubber washer.  It had been pushed in (so it was concave, rather than the usual convex) and that was just enough to tickle the check valve into leaking.  I removed the washer/screen, pushed the screen back into shape with my finger and reinstalled.  Took 30 seconds and fixed the issue. 

Might want to check that.  Really simple thing, but that's where troubleshooting should always begin.  :)
 

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