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Author Topic: Hot water overflow  (Read 15033 times)

Tom

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Hot water overflow
« on: March 11, 2005, 07:56:37 PM »
This question relates to our boat, but it could just as well apply to the coach, since both use a similar hot water system (the HW tank on the boat is larger)....

If I leave the hot water heater on, eventually I hear the water pumps cycle on and off. I also see water coming out the side of the boat. If I ignore it or, like last night/this morning, I don't catch it, It will eventually empty the fresh water tank. My temporary "fix" is to heat the water and turn off the water heater. This problem started about a year ago, and didn't exist prior to that. What I'm suspecting is that there's a heat or pressure operated safety valve that's malfunctioning &/or the thermostat isn't working. Anyone seen this problem?
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Ron

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Re: Hot water overflow
« Reply #1 on: March 11, 2005, 08:50:00 PM »
Could very well be the pressure relief valve on the HWT.  If you can get to the HWT you should be able to see the brass pressure refief valve. Somtimes just pulling the lever to manually operate the valve will allow debris to wash out from the valve seat area.  If that doen't work replace the valve.
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Steve, CDN

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Re: Hot water overflow
« Reply #2 on: March 11, 2005, 09:11:15 PM »
Tom,

In addition to Ned's suggestion about activating the lever on the pressure control valve, I regularly flush the HWT using a contraption I made that attaches to a garden hose, but is curved 90 degrees on the end.  It is surprising the amount of deposit I flush out of the tank every three or four months.

When I flush the tank, I replace the inexpensive plastic drain plug (75 )as the head can easily shear off from the torque stress when tightening more than once or twice.
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Tom

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Re: Hot water overflow
« Reply #3 on: March 11, 2005, 09:16:22 PM »
Thanks Ron. It's easy to get at; Lots of romm below decks. I'll press the lever in the morning.
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Tom

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Re: Hot water overflow
« Reply #4 on: March 11, 2005, 09:18:15 PM »
Do you by any chance have a photo of the contraption Steve?
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Ron

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Re: Hot water overflow
« Reply #5 on: March 11, 2005, 09:22:34 PM »
I have a device I bought at camping world that I use to flush the water tank.  Can take a photo tomorrow and post it.
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Tom

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Re: Hot water overflow
« Reply #6 on: March 11, 2005, 09:31:07 PM »
OK thanks Ron.
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Steve, CDN

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Re: Hot water overflow
« Reply #7 on: March 11, 2005, 09:39:10 PM »
I don't have a photo with me, but when we return to the coach in a couple of days, I'll take a picture.  It originally was a device for flushing an outboard motor, which I sawed in half, sealed the open end with epoxy.  It's already made to be attached to a garden hose and is made with a 90 degree end where the water comes out.  Cost me nothing since I got it in a junk box from someone who was getting rid of it.
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Tom

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Re: Hot water overflow
« Reply #8 on: March 11, 2005, 10:09:01 PM »
You mean half a pair of fushing ears like these?
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Steve, CDN

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Re: Hot water overflow
« Reply #9 on: March 11, 2005, 10:23:12 PM »
You mean half a pair of fushing ears like these?

Yes, exactly.  Now those cups have to be discarded and the cups are attached to a 90 degree fitting which can be extended for better fit into the tank drain opening for flushing.

Thanks for the photo link!
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Tom

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Re: Hot water overflow
« Reply #10 on: March 11, 2005, 11:23:47 PM »
I'm still having a tough time visualizing it Steve. Maybe I shoul wait for your photo  :)
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Gary RV_Wizard

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Re: Hot water overflow
« Reply #11 on: March 12, 2005, 08:09:56 AM »
Just about any small nozzle that you can stick in that little tank drain hole will help flush the silt out of the tank.  A lot of it can accumulate in a short time, depending of course on the salts in the water you use.  However, I don't see how silt could cause your overflow problem - that's got to be either the relief valve or a crack in the tank.  The relief valve could be opening early or just have a bad seal (usually neoprene), but it is also possible the tank actually is overheating and the relief is "working as designed".  ???

Another thing that will sometimes cause a relief valve to "weep" is lack of an adequate air "head" in the heater tank. There should be a cushion of air at the top. Assuming the relief valve is in the side of the tank a little below the top, the technique is to open the relief and let water drain until it stops, i.e.the water is just below the level of the relief. That assures there is an air cushion.  However, if the relief valve seal leaks, the air cushion will disappear over time and you will have to repeat the process (or replace the valve).
Gary
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Tom

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Re: Hot water overflow
« Reply #12 on: March 12, 2005, 09:55:51 AM »
Quote
it is also possible the tank actually is overheating and the relief is "working as designed".

That was my first choice Gary. When I get out of my PJs I'll go down below and check it out.
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Dolphin Jockey

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Re: Hot water overflow
« Reply #13 on: March 12, 2005, 10:38:40 AM »
Hi Folks,

FWIW, I'm not a fan of using the PTR valve to put an airhead in the water heater.  Years ago I read somewhere that it's an invitation to problems with deposits clogging the PTR valve and affecting its proper operation.

There's another way to place an airhead in the water heater: pump it in through the water hose between the RV and the campsite hookup.  Before connecting the water hose to the RV ensure it is drained completely.  Turn on any hot water faucet at a sink in the RV.  Now connect the outside water hose to the RV and turn on the outside spigot.  As water flows into the RV it will force air ahead of it into the water heater.  Once the proper airhead is established any excess air will flow out through the open hot water faucet.  Allow the air+water to flow until there no longer are air bubbles coming out,  You now have a proper airhead without messing with the PTR valve.
Best regards,
George

2005 Dolphin 37'
2001 Saturn SW2
FMCA #196968

Tom

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Re: Hot water overflow
« Reply #14 on: March 12, 2005, 11:14:06 AM »
Thanks for posting that information George. A couple of questions/clarifications:

  • I assume you're saying to hook up to the "city water" inlet vs using the gravity feed (?)
  • Why doesn't the air get pushed out of the open facuet?
« Last Edit: March 12, 2005, 11:15:48 AM by Tom »
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Ned

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Re: Hot water overflow
« Reply #15 on: March 12, 2005, 08:19:44 PM »
After draining and flushing my HWH, I leave it empty and when I turn the water back on, the air in the tank creates the airhead.

Tom, the water enters a hot water tank at the top and leaves from the bottom, so as soon as the exit is covered with water, the remaining air forms the airhead.  The result is much the same as my method.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Tom

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Re: Hot water overflow
« Reply #16 on: March 12, 2005, 11:16:52 PM »
Quote
the water enters a hot water tank at the top and leaves from the bottom

Thanks Ned, but color me confused.  ???  It's been many years since I worked on domestic hot water heaters for a living, but they always used to have cold water coming in the bottom and hot water out the top. Any reason that RVs would be different?
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Ron

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Re: Hot water overflow
« Reply #17 on: March 12, 2005, 11:41:15 PM »
If I recall correctly  the cold water should enter near or at the bottom and hot goes out near the top.  If the cold was to enter the top the cold water would cycle to the bottom cooling the heated water and the water heater would be very inefficient.



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Dolphin Jockey

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Re: Hot water overflow
« Reply #18 on: March 13, 2005, 12:41:12 AM »
I assume you're saying to hook up to the "city water" inlet vs using the gravity feed (?)

That's correct.  Let the city water pressure force air from the empty hose into the RV ahead of the water.  By having a hot water faucet on before the city water is turned on the air will be forced to flow into the water heater.

I've read the other posts addressing air coming out the hot water faucet and I agree with Ron.  On my Suburban water heater cold water enters at the bottom of the tank.  Hot water comes out NEAR the top of the tank, not AT it.    If air is pushed in at the bottom of the tank it will rise to the very top.  As long as the water level is BELOW the hot water outlet air will escape via the open hot water faucet.  Once the water level rises TO the outlet you get a combination of water and air out of the faucet   Force more water in the bottom and the air at the top will start to compress, allowing the water to rise slightly above the hot water outlet.  Once that happens you no longer have air coming out of the faucet, even though air remains at the top of the tank.

That airhead is necessary because water expands when heated.  As it expands the airhead compresses.  That's why there's a sudden rush of water when you first open a hot water faucet after the water heater goes through a heating cycle.  If that airhead were not there then there would be considerable leakage of water out the PTR valve as the water is heated.

Hope this helps.
Best regards,
George

2005 Dolphin 37'
2001 Saturn SW2
FMCA #196968

Ron

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Re: Hot water overflow
« Reply #19 on: March 13, 2005, 01:17:10 AM »
Excellent explanation George.  That is as I understand it'
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Tom

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Re: Hot water overflow
« Reply #20 on: March 13, 2005, 02:09:22 AM »
Thanks for that explanation George. Very clear.
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Ned

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Re: Hot water overflow
« Reply #21 on: March 13, 2005, 08:05:25 AM »
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.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Tom

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Re: Hot water overflow
« Reply #22 on: March 13, 2005, 08:38:50 AM »
Nice one Ned  ;D
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Ron

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Re: Hot water overflow
« Reply #23 on: March 13, 2005, 08:54:29 AM »
Your excused Ned.  I figured it was the computers fault you got the lines crossed. ;D ;D ;D
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Gary RV_Wizard

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Re: Hot water overflow
« Reply #24 on: March 13, 2005, 09:16:25 AM »
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.
Gary
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Ned

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Re: Hot water overflow
« Reply #25 on: March 13, 2005, 10:11:47 AM »
Quote
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.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Karl

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Re: Hot water overflow
« Reply #26 on: March 13, 2005, 01:06:50 PM »
Not to be picky Tom, but if you push on the lever, you'll be pushing all day - you have to LIFT it! (Unless it's some kind of Briitish Isles model) ::)
Karl (Cheesehead) Kolbus   Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "...holy cow ...what a ride!"

Ron

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Re: Hot water overflow
« Reply #27 on: March 13, 2005, 03:32:17 PM »
Tom,

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

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Dolphin Jockey

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Re: Hot water overflow
« Reply #28 on: March 13, 2005, 04:51:34 PM »
Attached is the photo of the tool I use to flush the water heater.  Be suprised how much stuff washes out.

The "Tank Saver Flushing Tool" is available at both Camping World and Camper's Choice for under ten bucks.  See it at http://www.camperschoice.com/Product.cfm?productGroupID=2560&showlowestprice=Yes
Best regards,
George

2005 Dolphin 37'
2001 Saturn SW2
FMCA #196968

Ron

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Re: Hot water overflow
« Reply #29 on: March 13, 2005, 05:13:44 PM »
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.
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