Forum Discussion

oldtrojan66's avatar
oldtrojan66
Explorer
Nov 14, 2016

Hot Water Issue

Hey, Kids! There are a couple other posts nearby, that are close to my issue, but not close enough that I feel like hijacking their threads.

My issue, which I have had for some time is just wierd. Hers' what I know. When I turn on the heater in a full tank of water, it gets hot. Electric or propane, no matter. However, when I turn on the hot water, it is hot for only about 5-20 seconds, then goes to luke warm. Here's the fix. I must turn off the pump, open the drain plug, open the temp/press relief valve, and let about 2-3 gal run out on the ground. This is all hot water (the whole tank, actually, if I let it all out!). Put drain plug back in, close TPRV, turn pump back on and fill water tank by opening a hot water faucet. Turn heater back on, wait a bit and, voila! Hot water for shower, dishes, etc.

One other factor that may or not be relative. When the heater only produces 10 seconds of hot water, the pump will spontaneously run for about 1 sec, every couple hours, without running water. I have searched, diligently for any kind of leak, to no avail. Nothing, Nada, Zip! Everything I can see is dry! When the hot water continues to flow, this does not happen!

Here's what I'm thinking; There is supposed to be a bubble in the top of the heater tank, and when it's not there, the cold water mixes with the hot too quickly and turns luke warm. When the bubble is present, the mixing is correct.

Question; what happens to the bubble in the tank? Is it related to the pump running on it's own? Is there any other reason for the pump to run, other than a pressure drop? If not, why is there no water leaking when the system is under pressure all the time? What is there about this bubble, that I can't find any information about it anywhere?

I know someone out there in RV land will have the answer for my questions and I thank you sincerely in advance for the help!!! David
  • Dick_B's avatar
    Dick_B
    Explorer
    Nov 14, 2016
    May not be relevant but is there some kind of a bypass valve cracked open?
  • westend's avatar
    westend
    Explorer
    Nov 14, 2016
    I'd suggest that you check the position of any bypass valves in your system. If the water is hot in the heater tank, you should get hot water out of a faucet, regardless of any air pocket in the heater tank. There are some newer heaters that have a mixing valve where the water is heated hotter and cold water is mixed into the hot water supply. You may also have air locked the heater tank by not opening a hot water valve when filling the tank. That is essentially what you are doing with your "after-heating" process. I don't like using the TPRV for anything. I've had too many problems with broken O-rings and poor seating.

    Pump runs when line pressure drops below a certain pressure level. This can occur because of a leak in the system, pressure deviation in the heater tank or lines, the pump leaking pressure back to the supply side.
  • Dutch_12078's avatar
    Dutch_12078
    Explorer II
    Nov 14, 2016
    The bubble disappears over time when the air is absorbed into the water. An external expansion (accumulator) tank, even the small one that Shur-Flo sells, will eliminate problems related to the disappearing air bubble when installed in the cold water line on the output side of the pump.
  • fpresto's avatar
    fpresto
    Explorer
    Nov 14, 2016
    If you have an outside shower make sure that the faucet handles are off not just the shower head. If open they allow the hot and cold to mix.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Nov 14, 2016
    First: Pump should not run between water use..
    Second: from time to time you do need to drain the water heater but every six to 12 months should be often enough.

    Finally normally the symptoms you cite are assoicated with the outdoor shower, Mixing valve open but cut off on head closed, The slow drip makes the water pump run and cold water bypasses the heater via the mixing valve outside.

    There are other causes however.
  • oldtrojan66's avatar
    oldtrojan66
    Explorer
    Nov 14, 2016
    Thanks for the replies! I forgot to mention I have been around the check valve block several times. It is working as designed. I have removed the entire water heater when I thought I would need to replace it. When there was nothing wrong found, I replaced the unit, and checked the valve and the plumbing around the heater. I understand how the check valve works for winterizing and it is a normal in-line gate valve with one red handle to move the internal parts 90 degrees. All that is okay. I understand the check valve is the first place to look, and I have done that. I have also checked the outside shower (which has never been used) and it is turned off. I'm just saying, the only thing that gets me a full tank of useful hot water is to drain part of the water out, refill with the air space at the top and reheat. I just don't know why this is so. Thanks, again, david
  • CT_WANDERER's avatar
    CT_WANDERER
    Explorer
    Nov 14, 2016
    Is this only when just hot water or are you mixing cold water with it? If when mixing Hot water and Cold water, Try to just run just hot water, see if the flow rate stays the same. I had problem with my CV. Water would start off hot but cool down when mixing hot and cold. With just Hot water you could see flow rate would drop down very low. Bad CV, I removed the internal parts to CV. No problem with the hot water now.

    See the OP just added some new information
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Nov 14, 2016
    Air pocket has NOTHING to do with you lack of HOT water FLOW

    Water is being heated (electric/propane) and is available
    Open a faucet and water pump runs causing hot water to flow out of water heater tank REGARDLESS f air pocket or no air pocket (air pocket is for control of pressure increase due to water swelling when heated---that is all it is for)

    Water coming out hot then turning luke warm....
    *COLD water has to be mixing with hot
    **Cold water can mix with hot thru water heater bypass valve (open or leaking thru)
    ***Cold water can mix with hot thru inside/outside showers not being turned off using cold/hot knobs
    *****Cold water can mix/dilute hot IF cold water inlet DIP tube has fallen off and cold water is no longer being directed DOWNWARD. (pointed down cold water creates a thermo barrier that pushes hotter water up/out.-----it not directed downward cold water can 'stream' upward and heavily cool the hot resulting in warm coming out)

    This is an Atwood.........Suburban also uses 'dip tubes'
    Need to look inside via drain hole or electric heat element opening etc and see if dip tubes are still in place

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