Hot and Cold water mix-up

I have a 2002 Four Winds Windsport which I purchased in April of this year. I have been having problems with the hot and cold water getting mixed up in the system. Sometimes hot water flows from the cold faucets and cold water from the hot. I first noticed this when I was getting hot water in the toilet. The kicker can happen when I'm on city water or using the water pump. I've noticed that the cold water inlet hose to the water heater will get hot when this happens making me think that there is a pressure problem and hot water is backing up through the cold water line. I've tried putting a check valve at the inlet to the water heater but then no water would flow from the cold water faucets. This doesn't make sense to me. Any help as to what might be causing this problem would be appreciated.


Senior Member
Re: Hot and Cold water mix-up

Is there any 'bypass' valve(s) on the heater (used when winterizing). If so, check that it/they are in the 'summer' position.
Re: Hot and Cold water mix-up

The water heater has the typical bypass system with shut offs at the inlet and outlet and a bypass shut off between the two lines. It doesn't seem to be causing any problems.

C Nash

Senior Member
Re: Hot and Cold water mix-up

If you have the shower head with the hose sometimes if you cut it off at the shower spray head instead of at the faucetts you can get a feedback of hot into the cold.
Re: Hot and Cold water mix-up

If you have mixer taps of the type that mix in the body of the tap rather than at the end of the spout the cold can push the hot back down the pipe & visa versa, the easiest way to stop this is to put check valves on the pipes where they join the tap,also a check valve on the inlet side of the water heater,if the water heater is the type that holds a few gallons then I think what happens is, when a cold tap is opened the pressure in the tank pushes waterback out of the tank and out the cold tapwhen you flush the john does the pump start straight away or is there a delay, if there is then I susspect that it might have a faulty switch,thus allowing the back flow, hope this is of some help good luck :) :) :)PS if you are doing what chelse is saying then it is a bad thing,not only will it cause the reverse flow but if the pipe failed and you wern't there you'd empty your tank over the floor!:(
RE: Hot and Cold water mix-up

Have you been running your heater/furnace when this happens? In some units (including mine), the heater ducts are poorly insulated, and thus can heat up water in nearby cold water lines.
Re: Hot and Cold water mix-up

Thanks for the responses everyone.
Here's what I did. I put a check valve on the inlet to the water heater. When the pump is on everything is now working fine. Hot water flows from the hot lines and cold water flows from the cold lines. Problem solved, right? As Lee Corso would say...Not so fast my friend. Now, when I connect to a city water connection, I get no water flow in any of the cold water lines. This is making me crazier than I already am. Any suggestions as to why this might happen?


Senior Member
Re: Hot and Cold water mix-up

Sounds like the fill valve is turned on to fill the fresh water tank (that is where the pump would pull water from). Might want to check that and turn it off when using city water. Just a thought. Also, check inside the hose connection on water inlet to make sure the back flow valve is not stuck (push in but watch out for water flow coming out).
Re: Hot and Cold water mix-up

In response to S. Harrington, I agree, that seems like the simple fix and as I said in my previous post, that is what I did. But the problem is, now, when I connect the city water I get no flow in the cold water lines.