Water going from hot to cold when using pump.

robthreedee · Apr 18, 2011

When using the pump, the water goes back and forth from hot to cold. Makes it kinda hard to take a shower. LOL Seems to work fine on city water (non-pump).

Anyway..what the heck is this all about?

Water Dog · Apr 18, 2011

Make sure your outside shower head is turned off at the valves, and not just at the showerhead. Also make sure your waterheater bypass valve is closed. Either one of those conditions will let cold water migrate into the hot water lines.

Gary RV_Wizard · Apr 18, 2011

You may also have left the fresh tank fill valve open (directs water from city inlet to fresh tank. In some systems this can cause hot and cold water to mix.

Please include year, make and model of RV when asking questions. It helps a lot.

robthreedee · Apr 20, 2011

thanks...that did the trick

robthreedee · Apr 20, 2011

I spoke to soon.

The fresh water fill bypass is in the closed (non tank filling) poaition, the hot water bypass valve is in the flow normal position. The outside shower head is off.

When the shower, or any other faucets, are turned on the pump goes off and on while pumping the water. When the pump comes on the water turns ice cold, completely leaving the hot water out of the equation. It alternates cold and hot back and forth like this, not every few minutes, but every few seconds.

Jeez I hate these mysteries. LOL

Thanks

Alfa38User · Apr 20, 2011

The outside shower head is off.

Not only does the outside shower head have to be off, the other taps have to be off as well (unless that what you meant!)...

robthreedee · Apr 20, 2011

Alfa38User said:
Not only does the outside shower head have to be off, the other taps have to be off as well (unless that what you meant!)...

I made sure all other faucets of anykind were off..no leaks or anything. There's uneven pressure when using the pump as well. That leads me to believe a possible bad pump?

Water Dog · Apr 20, 2011

What is your current configeration? Do you have a hose connected to the city water inlet or are you just trying to draw water out of your tank via the pump?

robthreedee · Apr 20, 2011

Water Dog said:
What is your current configeration? Do you have a hose connected to the city water inlet or are you just trying to draw water out of your tank via the pump?

There is a hose connected to the city water inlet, however, the water is off (the same as being disconnected right?) So I'm using the pump only.

Water Dog · Apr 20, 2011

robthreedee said:
There is a hose connected to the city water inlet, however, the water is off (the same as being disconnected right?)

Should be...in theory, unless the valve is leaking by. I think I would disconnect it just to verify that it's not giving you a problem. If you are using water from the tank and open a faucet wide, the pump should remain on and not cycle. Is that what is happening?

robthreedee · Apr 20, 2011

Water Dog said:
Should be...in theory, unless the valve is leaking by. I think I would disconnect it just to verify that it's not giving you a problem. If you are using water from the tank and open a faucet wide, the pump should remain on and not cycle. Is that what is happening?

It's cycling when any faucet is turned on wide. I will disconnect the city water hose and report back.

Disconnected the hose. No change...

Water Dog · Apr 20, 2011

Welllll...my guess is a pump, but it would be nice to verify it. I don't know why that would cause a loss of hot water unless it just wasn't putting out enough volume to push it through the water heater and was kind of taking the path of least resistance through the cold lines. If there was a place to put a pressure gauge in the system somewhere, that should give a clue. What would happen if you opened two cold water valves...say one close to the pump and one further away (maybe like bathroom sink and kitchen sink)? would the one further from the pump put out any water?

robthreedee · Apr 20, 2011

Water Dog said:
Welllll...my guess is a pump, but it would be nice to verify it. I don't know why that would cause a loss of hot water unless it just wasn't putting out enough volume to push it through the water heater and was kind of taking the path of least resistance through the cold lines. If there was a place to put a pressure gauge in the system somewhere, that should give a clue. What would happen if you opened two cold water valves...say one close to the pump and one further away (maybe like bathroom sink and kitchen sink)? would the one further from the pump put out any water?

let me get back to you on that...it's starting to storm out.

boatbuilder · Apr 20, 2011

I am also wondering if there is a check valve issue at the water heater. If the check valve is stuck or obstructed it might cause issues.

bigpemby · Apr 20, 2011

I had a check valve on the cold water inlet and one on the hot water outlet of my water heater. Turned out they were both bad. I had all sorts of pressure problems and intermittent hot water issues. Cheap parts to replace, mine were hard to get to, but sure glad I did it. Everything is great now.

Water Dog · Apr 20, 2011

boatbuilder said:
I am also wondering if there is a check valve issue at the water heater. If the check valve is stuck or obstructed it might cause issues.

bigpemby said:
I had a check valve on the cold water inlet and one on the hot water outlet of my water heater. Turned out they were both bad. I had all sorts of pressure problems and intermittent hot water issues. Cheap parts to replace, mine were hard to get to, but sure glad I did it. Everything is great now.

Sounds reasonable for the hot/cold pressure issue, but I would think that there would be something making that pump shut off with faucets wide open...unless the cold was being supplied through a check valve that was intermittently closed.

WhiteEagle · Apr 20, 2011

I think you addressed it when you mentioned you had all hot and cold faucets off including the outside showerhead ... but just like the outside spray head, both line faucets have to be off on inside shower also?

Ned · Apr 20, 2011

If there is an accumulator in the fresh water system, the pump may cycle even with multiple faucets open.

Water Dog · Apr 20, 2011

Ned said:
If there is an accumulator in the fresh water system, the pump may cycle even with multiple faucets open.

Good point, but one of the OP's statements was that the system worked okay on the city water hook up. The check valves etc. are the same at the water heater end. The only thing that's changing is the supply.

Ned · Apr 20, 2011

Dennis, I know, I was only addressing the pump cycling with several faucets open. That may be normal and not part of the original problem.

Water going from hot to cold when using pump.

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