Hot water overflow

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
Thanks for that explanation George. Very clear.
 
I'm going to use the party as my excuse for getting my hot and cold reversed :D  Of course, the hot water comes out the top where it's the hottest.  However, the rest of my procedure is correct.  The end result is the same as George's, just a different path.
 
I'll concede that use of the PTR can conceivably result in a problem, but in my opinion debris is not much of a  concern. If a bit of sand or lime crystal gets caught in the seal, merely opening and closing the valve again will flush it out.  Frequent use of the PTR can, however, result in deterioration of the PTR's rubber seal, resulting in seepage - the PTR is not designed for every day use like a faucet valve.  On the other hand, occasional opening of the PTR will keep the rubber seal  from sticking, a not uncommon problem with PTRs that have not opened for years.  The occasional use we are talking about here, maybe a couple times a year, is not something I lose any sleep over.  However, the alternate methods work too - with perhaps a bit of running back and forth to open/close faucets if you don't have an outside faucet handy.  Like George recommends, I routinely open a hot water faucet after connecting to city water so that any air in the line bubbles through the heater tank, just to be sure the air head is maintained.

For some  reason, when I  flush and refill my heater the tank usually overfills, or at least ends up with a very small air head. I like to start out with a nice one, so opening the PTR "adjusts" it in a jiffy!

BTW, you won't get any air into the heater tank if a gravity fill is used. The air bubbles back out the fill port rather than being forced into the tank.
 
BTW, you won't get any air into the heater tank if a gravity fill is used. The air bubbles back out the fill port rather than being forced into the tank.

That's why I start with an empty tank.  You can then fill it from either the city water or the onboard pump.  I have never seen a hot water tank with a gravity feed, only the fresh water tank.
 
Tom,

Attached is the photo of the tool I use to flush the water heater.  Be suprised how much stuff washes out.

 

Attachments

  • Water heater flushing tool.JPG
    Water heater flushing tool.JPG
    39.4 KB · Views: 24
Well worth the money.  I always make one of my normal water tank flushes when we are at VIP campground in SLC, UT.  They consistanly have very high water pressure.  Makes for a good clean out.
 
Thanks all for the help. I didn't get to look at the problem this weekend, but will be getting to it during the week.
 
Does the water still leak out before you turn on the water heater?  If it doesn't it is a pretty good indication you have NO head of air in the water heater.
 
Ron

It only comes out when the heater has been on for some time. If I then shut off the heater and run a hot faucet for a short while, effectivly cooling the water in the tank, it stops. That's why I originally thought the thermostat wasn't doing its job and the water overheating.
 
As the water it expands with nor head of air the water cannot compress so the excessive pressure causes the pressure relief valve to open.  First thing I would recommend is restore a air head by either opening the pressure relief valve till the water stops runnng out or using one of the other recommended in this thread.  I'm quite sure that will correct the anomaly.
 
You can put a head of air in the hot water heater, but that's really just a band-aid.

The real problem is the RV has a sealed water system , with checkvalves at the water pump and at the city water system.? ?The water in the hot water tank expands as it heats up.? In a conventional house the expanding water can backflow into the cold water inlet line, eventually dissipating through the main water inlet to the house.? ?In a RV the checkvalves prevent backflow, so when the water expands in the hot water tank, there's nowhere for it to go.? The system pressure rises until the overtemp/overpressure valve weeps.

An air bubble in the top of the hot water tank will eventually be absorbed into the water.? ?The permanent solution is to install an accumulator tank on the cold water side of the system.? The accumulator has a membrane seperating the air from the water so the air pocket stays intact.? The easiest place to install an accumulator is usually at the outlet of the water pump, but it could be installed anywhere in the system.? The permanent airspace in the accumulator gives the expanding water some place to go, so the system pressure stays normal instead of popping off the overflow valve.
 
Lou

I have an accumulator tank after the dual water pumps. Now you have me wondering why it doesn't act as the equivalent of an air pocket and allow expansion of the water.
 
You have to make sure there is no check valve between the accumulator and the water tank. What Lou mentioned about the head of air dissipating happens.  However, in our case between letting air from the hose enter the system as some described ealier and flushing the water heater twice a year we never have any trouble with the head of air in the water heater dissipating.

 
OK thanks Ron. Looks like I have long list of stuff to fix &/or install this week (month?)
 
Back
Top Bottom