hot water from cold faucet?

[utahskierdave]

I have a 2003 Coleman Carmel and for the last 2 seasons I am getting a short blast of warm water when I use the cold faucet.  The water starts cold, then warms significantly for a moment before getting cold again.  This happens even when the outside temp is cool so I don't think the ambient temp is warming the water in the plumbing.  Any thoughts as to the cause and what I can do to fix it? Thanks.

[hoppy]

Does this happen while you are set-up to the city supply line, or when using the on-board water?

 If it's the city side option, I think you would be surprised how hot the water can get in the coiled hose lying out there in the direct sunlight.

  This is what I think it may be.

 PS: If this is the cause of the problem, place the water hose under the PU.

[He Ruide]

I agree with Hoppy.  One way to verify this is to check the temperature of the hose that is between the spigot and the PUP.

Ruide

[PattieAM]

I agree with Hoppy - I've had that issue as my hose was carefully coiled and was receiving the morning sun - hotter than the water out of the water heater (which I hadn't even lit).  Afternoons weren't as bad as the PUP provided shade over the hose.

[He Ruide]

Well folks I have to a new theory and I waiting for Dave to say that it occurs when he is getting water from his tank and not city water as we all assumed.

I'm currently camping with no water connection.  This morning as I was washing up dishes I noticed the cold, then warm then cold phenomena that Dave mentioned.  I have to confess at the first time I thought I had turned on the hot water but I hadn't.  It kept occurring over and over again until I finally realized it was from the water pump.

Yes anytime the water pump kicks on seconds later I would get some warm water then it quickly got back to cold. It might simply be that if the water pump is coming on and off, then the water that sits in the pump warms up and hence you get the cold water that is in the line, followed by the warm water that was sitting in the pump followed by cold water from the tank.   I did not think that my water pump got that warm and I can't remember every experiencing this... so maybe I have a defective pump which I'm dying to have so I can buy a Whisper King.  So, if I get a chance today I'll pull open the kick plate and see how warm the pump gets normally.

Ruide

[Rauch0812]

This is interesting because I've experienced the same thing... but the water that has come out of my faucet (when hooked to city water) was HOT and lasted for quite awhile when doing the dinner dishes. Several times.  I felt certain there was something crazy with the plumbing.

My husband had the theory that the hot water line sitting unused next to the cold water line builds up enough heat to head the cold line next to it... who knows, just a thought...

[utahskierdave]

Dave is camping locally - he just called me (his wife) on the phone to check up on this thread.  This is what he said.... We never use city water, we are always dry camping.  So I turned on the faucet and I get about 12 oz of cool water before it gets hot and 12 oz of hot water before it gets cool again and thats when the pump kicks on and stays cool.  Maybe it is because the hot water line and cold water line are next to each other, like one of you suggested.  Maybe I might try putting some insulation on the hot water line for the next trip?  Anyone have any ideas about this please let me know.  Thanks so much for the feedback!

[utahskierdave]

So much for the hot water line heating up the cold water line theory... The faucet exhibits the same behavior (12 oz cold / 12 oz hot / back to cold) when I turn it on less than a minute after it was turned off.  Any thoughts?

[suprz]

I had the same thing happen to me last time i was dry camping.  i figured it out to be the hot water heater, heating the water which creates pressure and back feeding into the water lines.  I never had this happen before even when dry camping.  this time however i had shut off my water pump when i wasnt in the camper and left the hot water heater on.  once i turned on the water pump and ran the cold water till it was cold again, and then left the water pump on so it would keep pressure on the system, it never happened again.

[utahskierdave]

So, while I was on my last trip my wife read your replies and I tried some experiments....I get the cool/hot/cool phenomenon when I turn the faucet on and off in quick succession so I don't think it has anything to do with the proximity of the cold water line to the hot. If the pump was heating the water as it passes through wouldn't it stay warm as the pump warms? I think suprz is right in that the cold water line is sucking water from the hot water line.  Can anyone tell me what the fix is?

[Ira_P]

Back flowing of hot water into the cold water line can be caused by air trapped in the hot water heater. This causes the hot water heater tank to act as a pressure tank. When the faucet is closed, the water pumps runs building up pressure in the whole plumbing system including the water heater tank. When you open the cold water valve, the pressure drops and hot water will flow back out through the cold water inlet line until the pressure is equalized.

Fix -- make sure you run the hot water to remove all the air in the tank or install a check valve on the cold water inlet line running to the hot water heater.

Ira

[He Ruide]

Ira,

Interesting hypothesis.  In my case the hot water came out at the same time the pump kicked on hence my link to the pump.

Restating what you said, once you turn off the cold water the pump pressurizes the system.  When you turn on the cold water you:

1. first get the cold water that is under pressure,
2. followed by a little hot water back flow from the water heater air pocket and
3. as the pressure drops further the pump kicks on you get cold water from the pump that is at a higher pressure than the declining hot water back flow.

Maybe a quick  way to confirm your hypothesis would be to feel the cold water pipe inlet to the hot water tank.  It should be warm before the pump kicks on then colder as cold water is pumped back in to replace the hot water that just flowed out.   Alternatively, if you have a winterizing by pass valve - by passing the heater should prevent the issue.  If either of that happens then you are right on.

Ruide

[utahskierdave]

Ira,  Do you mean that I should just open the hot water tap when I first pressurize the system on initial set up or each time I use the faucet?  Or do you mean I should vent the hot water tank using that pressure valve outside on the tank?

[oreo57]

after reading this it seems to me that of the 3 check valves the one on the cold side line leading to the water heater may be going bad, because that one is supposed to stop hot water from backing into the cold side. the other ones are on the inlet side of city fresh water to stop the pump from pushing water out that port and the other on the outlet on the pump so you dont fill the holding tank when on city water .
 
Also remember that a water heater is a pressurized vessel thats why you have a T&P valve on it, to relieve excessive pressure.

[Ira_P]

I always vent the hot water tank when hooking up the water by running the hot water through the faucet. Sometime, I get air in the system from the hooking up the hose, ( being empty and full of air ) and it always seems to get trapped in the hot water heater. I have seen it back flow hot water to the cold side before, but with venting it is rarely happens. Sometime this fall, I will add in a check valve prior to the hot water heater. This solved the problem for our friend's Niagara.