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Thread: Shutting down natural gas water heater for 2 to 3 weeks

  1. #1
    DIY Junior Member BobS0327's Avatar
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    Default Shutting down natural gas water heater for 2 to 3 weeks

    I have a GE Power Vent, Model GG50T06PVT natural gas water heater. I plan on going on vacation for two to three weeks and I will shut the water off to the house at the main shutoff. I also plan to turn the power off to my GE natural gas water heater.

    Thus, my question is: Will shutting off the water and electric to my natural gas water heater for two to three weeks cause any potential issues? Also, will I have any potential issues upon returning from vacation and turning the water and electric back on to the water heater?

    Thanx

  2. #2
    Moderator & Master Plumber hj's Avatar
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    None as long as the heater does NOT decide to start leaking while you are gone.
    Licensed residential and commercial plumber

  3. #3
    DIY Senior Member Chad Schloss's Avatar
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    Quote Originally Posted by hj View Post
    None as long as the heater does NOT decide to start leaking while you are gone.
    hate to rain on his thread, but my question is similar: is is better to drain the heater or leave it full with the water off? I am renovating that house i am working on and hooked up a similar water heater and have it filled with water. i have turned it on once in awhile to make sure it still works, but i have been leaving it off, since i have no use for the hot water yet. is it better to keep water in the tank to stop it from rusting? would it be better to leave it on the vacation setting or have it shut off? thanks

  4. #4
    Test, Don't Guess! cacher_chick's Avatar
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    If you are leaving for only 2-3 weeks, I recommend leaving it alone. Turning it off or draining it would be more likely to cause harm than good.

    The standby losses on the water heater are very small. With no water use, it costs very little to keep the water in the tank hot. There are several downsides to shutting things off. Anytime a system loses and regains pressure, it will loosen particles in the piping sytem. Tanks and piping with exposed iron will experience accelerated corrosion when drained. Turning the heater down or off can promote growth of bacteria and/or diseases such as legionnaire's.

    In most cases it is best to just close valves supplying appliances with hoses such as a washing machine.

    A good neighbor or service to check on things once in a while would be a better idea than shutting everything off.
    Last edited by cacher_chick; 12-27-2011 at 03:45 PM.

  5. #5
    DIY Senior Member dlarrivee's Avatar
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    I think if you drain the hot water tank before leaving for a week, you should start wearing a tin foil hat as well.

  6. #6
    In the Trades Gary Swart's Avatar
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    I have a GE/Rheem power vent and it has a vacation setting on the thermostat. As others have noted, it costs very little to keep the water hot when none is being used. I'd use the setting provided by the manufacturer for this purpose. Even if you didn't turn the 'stat down at all, the cost of maintaining the temperature would be so small I don't think you could buy a cup of coffee with the savings.

  7. #7
    General Engineering Contractor ballvalve's Avatar
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    So lets leave our lights all on by the same philosphy. Parasitic losses in transformers and TV's etc. earthwide could heat Russia for a year.

    Since most water heaters have hot surface igniters or spark igniters, turning them off is the same as a light switch.

  8. #8
    Master Plumber master plumber mark's Avatar
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    Default leave it alone

    it would be wiser to just set it on low
    or vacation, even with the water to the house off
    it wont hurt anything...

    Ge powervents are not the easiest things to get parts for
    especially when you get home from vacation and want to
    take a hot shower.....

    So when you turn off something like a GE power vent
    you run the risk of it just decideing not to jump back
    to life when you come home.....then you are in for some fun.

    also, you would have to be nuts to drain it

    leave sleeping dogs lie......

  9. #9
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    LOOK AT THIS ABOUT WHAT HAPPENS WHEN HOT WATER IS LEFT FOR A COUPLE OF WEEKS


    Every reader of this column is intimately familiar with cow tipping and, undoubtedly, spontaneously combusting bovine mammals. For the following twist on that same theme, I need to thank Lt. Phil Lyons, Fire Prevention Officer and Investigator with the Tukwila Fire Department, for sharing an article with me on the killer in our kitchens disguised as a dishwasher. Yes, a dishwasher - a potentially murderous dishwasher. It seems a U.S. Navy housing inspector was doing a routine bi-monthly check on vacant buildings at his base. His normal routine was to flush the toilet and run the dishwasher while he proceeded with the rest of the inspection.

    But on this particular day, three minutes after he started the dishwasher, it exploded. The appliance was driven across the kitchen, damaging the plumbing, cabinets and wall; plus it blew apart the rear door of the building.

    Investigators initially surmised water in the "P" trap had evaporated, allowing sewage gas to enter the dishwasher and explode. Methane gas produced by decaying vegetable matter has been known to combust on occasion when it leaks from sewage systems. Alas, methane was not the problem they soon discovered.

    According to the article, one of the investigators found a little-read paragraph inside the owner's manual about hydrogen-gas production in hot-water systems.

    It seems hydrogen gas can, under certain conditions, build to unsafe levels in systems that have not run for two weeks or more.

    The investigating engineers explained that because of the way the hot-water-heater tank was constructed, there was no way to stop the production of hydrogen gas.

    Hydrogen isn't water soluble, and it remained in the plumbing system as a gas under pressure.

    The gas normally migrates to the top of the plumbing system, where it is drawn little by little from faucets, thus becoming part of the greater atmosphere.

    In homes where the hot water is not drawn regularly, and a lower-level faucet or appliance is used first, the gas is forced out at that level.

    The theory behind this explosion was that the hydrogen was ignited by the timer or relay switch inside the dishwasher because hydrogen gas has an extremely wide range of flammability and will explode at just about any mixture, if a source of ignition is provided.

    This was the first exploding dishwasher on record. People in the water-heating industry say that a washing machine is known to have exploded in the 1960s.

    And several small fires at faucets have occurred when hydrogen gas was relieved next to a burning cigarette.

    Safety investigators recommend that occupants who have been away from a building for an extended period of time first run their hot-water faucets to relieve gas. And they should not smoke while doing so.

    The article did not say whether turning off a hot-water tank that isn't going to be used for several weeks eliminates the problem.

    Is this heat-related, or a chemical reaction that happens whether the water is hot or cold? Readers, share your knowledge, please.
    Last edited by MACPLUMB 777; 01-03-2012 at 10:05 AM.

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  10. #10
    General Engineering Contractor ballvalve's Avatar
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    Hydrogen gas is an old time bomb in unused, running water heaters. Some do it and some do not, but its influenced by the water quality and the type of anode rod.

    Best and smartest to shut them off. And leave the water in.

  11. #11
    DIY Senior Member Runs with bison's Avatar
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    My advice, leave it at the normal set point, not on vacation setting, not empty, not off.

    Here is why: legionella bacteria thrive at the lower temps. Their ideal growth range is 95-115 F, and that appears to be precisely where the "vacation" settings will put it for several days as it cools off.

    I'm all for saving energy, but from what I've measured with a less efficient standard gas water heater the loss is about 1 ccf/gas use per 10 days when nobody is home and the water heater is left at normal setpoint.

    Related topic: timers for water heaters. I have the same issue with them. If the timer doesn't allow the tank to reheat after use, then the tank water temperature will stay in the danger zone for hours, perhaps 8+ hours. The timer will save very little energy in the process. Timers make economic sense for electric water heaters using with on/off peak rates. It's not about saving energy, but reducing charges for peak hour usages. And electric water heaters have much lower standby losses AND a much greater propensity to grow legionella in the first place.

  12. #12
    General Engineering Contractor ballvalve's Avatar
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    How many homeowners died of of legionnaires disease from hot water heaters this year?. Your home heater is not a Holiday Inn ballroom with miles of mouldy ducts and dirty filters.

    And if its so, those folks that throw money in the toilet for tankless heaters should drop like flies since their water is always in cooling off stage in the pipes and heat exchanger.

    There are millions of homes with 'open' - mine included and countless others I have installed- radiant heat systems where the hot water is constantly cooling to 50 or 60 degrees, being reheated, and often making it to fixtures at 115'. Havent had any lung, heart, asthma, disease or sudden deaths reported.

    So they took the lead out of valves, now the gov will make us keep our water at 150' f to "save" us.

    And here is the beginning of the BULL$%&^ dreaded OSHA wants us to test, never shut off a circulator pump, and eventually ban flow thu heaters. Just what we need.

    http://www.osha.gov/dts/osta/otm/leg.../hotwater.html

    They actually want the water in a hot water line to NEVER drop under 122f. Go for that plumbers!
    Last edited by ballvalve; 01-07-2012 at 12:32 PM.

  13. #13
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by ballvalve View Post
    How many homeowners died of of legionnaires disease from hot water heaters this year?
    More than 1 for certain, since there are between 8,000 to 18,000 cases of the disease estimated in the U.S. each year, and most homes have a water heater. In hospital settings the fatality rate is calculated as 28% and the source is primarily the drinking water (the same water that enters your water heater.) Various sources give the fatality rate as 5 to 30%. So a moderate guess would be around 2,000 deaths a year from the disease. Take your own guess as to how many came from water heaters.

    According to OSHA: "Domestic hot-water systems are frequently linked to Legionnaires' outbreaks."

    And from a study done in Quebec: "Domestic water heaters, particularly electric devices, can certainly be contaminated by Legionella. In Quebec, a study of 211 homes (178 electric water heaters, 33 oil or gas water heaters) found Legionella contamination in 40% of electric water heaters. No water heaters using fossil fuels were contaminated."

    And if its so, those folks that throw money in the toilet for tankless heaters should drop like flies since their water is always in cooling off stage in the pipes and heat exchanger.
    My experience designing, operating, and troubleshooting reactors suggests the opposite is true. The water in the tankless is going to get nice and toasty running next to heat transfer surface that tend to kill such things, and/or not sit around for more than a few minutes in the danger zone. Water in primary supply lines cools off quickly when not in use and is called for frequently (very high turnover rate), so legionella in "stagnant" lines is not a major concern to me.

    However, a water heater is a terrific biological reactor if conditions are right. Residence times are on the order of a day. So if there is any legionella in the incoming water, it will have the opportunity to propagate.

    There are millions of homes with 'open' - mine included and countless others I have installed- radiant heat systems where the hot water is constantly cooling to 50 or 60 degrees, being reheated, and often making it to fixtures at 115'.
    I would have to look at the design of the radiant system and see how they actually operate before I would commit one way or another. I don't have experience on this type of domestic system.

  14. #14
    General Engineering Contractor ballvalve's Avatar
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    Can america afford another set of regs that double the cost of plumbing and gas use? will we need silver lined water heaters and pipes? Every fixture on a hot recirculate full time? NOBODY died from a brass valve last year, but thats all going federal this year.

    Firesprinklers. Bad enough, now they will need full recirculate lest something grow in the pipe and someone breathe the mist when running from the home.

    Better build more overpasses and shopping carts - on a hot day the new hourdes of homeless can catch a shower from warm condensation dripping from the girders.

    Finally, they MUST ban swamp coolers as they are a proven receptacle for legions of leggionaires type microbes. Thats about 80 million people west of the Mississippi without cooling now. They drop dead pretty regular around here. Get the ACLU on it.

  15. #15
    DIY Senior Member Runs with bison's Avatar
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    I'm not buying into the hysteria/strawman, because that is not what I'm seeing and it has nothing to do with topic of legionella in a tank or tankless water heater. I don't see plans for recirculating every fixture.

    As for removing some lead from fittings, big deal. It isn't going to bankrupt us any more than low flush toilets, removing lead from other plumbing parts, higher efficiency AC's, furnaces, water heaters, TV's, banning CFC's, etc. have. I see opportunties for new U.S. products, rather than trying to compete on thin/negative margins in commodities (but good luck trying to convince conservative U.S. execs to invest in R&D, they are running their companies like dodos...headed down the same path to extinction.)

    Your lead argument is the same sort of one that would be used for lead plumbing, leaded gas, lead in paint, controlling emissions from lead smelters, etc.

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