A Physical Conundrum


James Hanley

James Hanley is a two-bit college professor who'd rather be canoeing.

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72 Responses

  1. Avatar aaron david says:

    How is your water pressure in the rest of the house?
    Is there water in the tank? Scratch that, you said there was
    Have you check all facets for hot?
    Does the out let pipe feel hot at the tank?Report

    • Avatar James Hanley in reply to aaron david says:

      We have checked all faucets for hot water including the washing machine.
      In all faucets the “hot” water pressure is noticeably weaker than usual, but there is flow.
      The outlet pipe at the tank is immediately adjacent to the exhaust pipe. The exhaust pipe is hot enough to cause a burn, as usual, but the outlet pipe is cold to the touch (and I do know how hot it normally feels).Report

      • Avatar aaron david in reply to James Hanley says:

        OK @james-hanley next question, Is water flowing into it?
        Also, what color is the gas flame? You want bright blue with just a hint of yellow at the tip. (If it is another color, you might not be getting enough gas to heat things)Report

      • Avatar James Hanley in reply to James Hanley says:

        My hvac guy thought the flame was fine, but we did turn up the thermostat to what would normally be well past the level that scalds, and still nothing.

        Inflow is an interesting question. There should be, but since it stopped flowing hot, we may not have drawn off enough to empty it if there is insufficient inflow to refill it. But we’ve run the taps quite a bit to see if the water ever got hot, and with the outflow at the top, I would assume it needs continual water flowing in to keep up the pressure for any outflow, no? So presumably, unless I misunderstand the dynamics, the presence of continued outflow should indicate continued inflow?Report

      • Avatar aaron david in reply to James Hanley says:

        Well, with lessened water flow, no hot and good flame, my guess would be that the pressure relief valve is open, letting water drain out hot. With the low pressure, I was kinda thinking the pump might be going, but but with no hot at the washing machine ( I am assuming it is right next to the heater?) it sounds more like hot is leaving the system early.

        Keep in mind I am not a plumber, and am only used to dealing with boilers for a large hydronic system such as your university uses and that was a long time ago.Report

      • Avatar James Hanley in reply to James Hanley says:

        Logical, but there is no drain for the water to flow to (the floor there is actually a couple inches lower there than in the rest of the basement, with the drain near the far wall), and no puddle; the floor around the tank is bone dry and dusty as always (a coal furnace once sat there–messing around by the heater and crawling into the crawl space, which I’ve done to replace pipe, insulate, and work on requiring, is a filthy business).Report

      • Avatar aaron david in reply to James Hanley says:

        Is it leaking at all in around the bottom? Also, is there and external pump?

        If it is not draining from a high temp, the only other thing I clould thing of would be a cracked heat exchanger, and a bad pump. If you think it is going bad for 5 years, it could be everything all at once.Report

      • Avatar James Hanley in reply to James Hanley says:

        Not leaking at all…yet, at least. No external pump.Report

      • Avatar aaron david in reply to James Hanley says:

        Sounds like a cracked heat exchanger on the inside, allowing water to collect in the base. At some point it will start leaking, so good on your guy getting it out.Report

  2. Avatar Michael Cain says:

    You’ve got an old house… some sort of “failed closed” whole-house anti-scald valve?Report

  3. Avatar Stillwater says:

    Water tank full in a system under pressure… You gotta block somewhere, yeah? Maybe at the exit port of the heater itself? Maybe on the input side (tho it should still drain for spigots lower than water level).Report

    • Avatar Stillwater in reply to Stillwater says:

      Ahh. Water is flowing thru the HW taps, yes? I see the conundrum.Report

      • Avatar Burt Likko in reply to Stillwater says:

        Pipes delivering water from the hot water tank should be warm. Perhaps (certainly) they are insulated, making that hard to gauge. But if hot water gets out of the tank at all, it should circulate throughout the house.

        Unless there is a flaw in the insulation and the pipes are being exposed to cold somewhere, cold intense enough and/or for a long enough period of time as to cool the water inside.Report

      • Avatar aaron david in reply to Stillwater says:

        @burt-likko all the pipes after the heater should be in the conditioned space of the house/basement.Report

      • Avatar James Hanley in reply to Stillwater says:

        Aaron has the right of it. Beneath my house is part basement and part crawlspace. The water heater sits in the basement immediately adjacent to a 4 foot wall, above which is the crawlspace under our kitchen, pantry, and dining room. The outlet pipe as it exits the tank is I insulated copper. I can lay my hand upon that uninsulated copper pipe as it exits the tank, which is usually uncomfortably hot, but is now cold to the touch.

        The tank itself has–or should have–an inlet pipe that reaches nearly the button of the interior of the tank, while the outlet is–or should be–at the top, with no direct connection to the inflow, so no possibility that a stuck valve is causing a bypass.

        And so I appear to have a tank of water sitting atop a flame without being warmed by the flame.

        The laws of physics appear to be in abeyance in my house.Report

      • Avatar Stillwater in reply to Stillwater says:

        I’m gonna go with a pressure leak in the tank. IF that’s the case, then water won’t flow thru the lines at the cold water rate (check) will effectively cool down water (check) and will create a flow rate such that hot will dissipate thru the lines on it’s way to the shower.


      • Avatar James Hanley in reply to Stillwater says:

        The water is not cooling down as it flows to the faucets–it is cold as it exits the tank. Does a pressure leak explain that?

        (To be clear, the pipes coming into our house seem to be shallowe than ideal, as our cold water is considerably colder in winter than in summer. Right now, the “hot” water is not cool, or “room temperature,” but the same temp as our cold water; I.e., extra cold.Report

      • The water is not cooling down as it flows to the faucets–it is cold as it exits the tank.

        Per comment above, is there another point where hot/cold cross over, as in a pressure-controlled anti-scald valve?Report

      • Avatar James Hanley in reply to Stillwater says:

        Where would such a valve be located?

        It seems unlikely, as almost nothing in my house was updated before we moved in except some of the first floor wiring and a few windows.Report

      • Avatar Hoosegow Flask in reply to Stillwater says:

        The laws of physics appear to be in abeyance in my house.


      • Avatar James Hanley in reply to Stillwater says:


        Heh, perfect.Report

  4. Avatar Kazzy says:

    “I have a tank full of water. I have a fire below the tank. ”

    Ummm… that’s how you get hot water in your part of the country?!?!?!Report

    • Avatar James Hanley in reply to Kazzy says:

      Sure. ?Report

      • Avatar Road Scholar in reply to James Hanley says:

        Natural gas isn’t a thing in New Yank. I’m sure his heater is electric.Report

      • Avatar Saul Degraw in reply to James Hanley says:


        New York uses oil for heating still. Maybe newer heaters are switching to electric.Report

      • Avatar Road Scholar in reply to James Hanley says:

        When I was in Connecticut we had an oil burning furnace and an electric hot water heater. I don’t even know if they make oil fired water heaters (at least for home use).Report

      • NG has become a New York/New England thing, just not in terms of residential use (takes decades to build out the distribution pipeline net). But a huge shift to NG for electricity generation. NERC’s biggest concern about reliability of the electricity supply in the New England region is now over-dependence on NG. Biggest problem for New England and NG use is that local New Yorkers are fighting tooth and nail against new/expanded NG pipeline systems crossing the strip from the Hudson to the Conn/Mass/Vermont border.Report

      • Avatar Kazzy in reply to James Hanley says:

        We’ve got NG. Just the way you described it made it sound like you had a campfire and a giant tank of water sitting atop it.Report

      • Avatar James Hanley in reply to James Hanley says:

        Right. You don’t?

        The kids are up at 5 kindling the fire so I can start the day with a hot shower.Report

    • Avatar Notme in reply to Kazzy says:

      I was wondering why he was consulting his hvac guy and not the plumber.Report

      • Avatar aaron david in reply to Notme says:

        A hot water heater, while definately part of the plumbing system, is often within the baliwick of HVAC (quite like a boiler/furnace etc.) Also, many hvac companies branch out into plumbing/electical during the winter as that is the slow season. Not to uncommon.Report

      • Avatar James Hanley in reply to Notme says:

        Fair question. Aaron’s got the right of it. I keep the guy’s “business card” magnet on my fridge, and it says “heating and plumbing.” Keeps a steadier income, I suppose.

        With our recent cold snap, he’s been dealing with a large number of burst pipes and overworked furnaces giving out.Report

  5. Avatar Road Scholar says:

    Do you have hard water? How old is your heater?

    We recently had to replace our heater due to a leak and our hot water flow and pressure is a lot better now. If your water is anything like ours you could easily have an inch or more of scale built up inside the tank, and significant buildup in your pipes. A chunk could break off inside the tank and clog the outlet (maybe?). Sorta like a blood clot and arteriosclerosis, bang! A stroke or heart attack. Pleasant analogy, huh? 😉Report

    • Avatar James Hanley in reply to Road Scholar says:

      Our water is medium hard, about ideal as far as that goes. But our water heater is at about 1.5 times it’s nominal life span. I’ve been expecting it to go at any time for the last 5 years. I’m not surprised if it’s gone kaput, I’m just trying to understand in what way it had done so. Given the age, scale is a near certainty even though our water is not very hard, but scale blocking either inlet or outlet would not prevent heating of the water.Report

      • Avatar Citizen in reply to James Hanley says:

        I’ve taken out tanks that 2/3 the volume was filled with hard water scale. Looked alot like cement. Its rare, but it happens. Hopefully it’s not that, because those damn tanks are HEAVY, not for the faint of back.Report

  6. Avatar Road Scholar says:

    Thinking about this some more… assuming your HVAC guy knows his stuff I think we can assume the fire is okay, the thermostat’s working okay, etc.

    It’s a weird failure mode (as you are already aware). The only thing I can imagine is somehow the water inside the tank is being prevented from circulating or there’s a layer of crap — I’m back to hard-water scale again because it’s a pretty effective insulator — lying on the bottom. Why or how something like that could develop all of a sudden is a mystery.Report

  7. Avatar North says:

    Clearly you have posted something offensive to either a group of conservatives or liberals and their collective hatred has caused the laws of thermodynamics to skew inside your hot water heater. Since conservatives hate with a hot hellish hatred and liberals hate with a cold visceral loathing I suspect the latter rather than the former. If some old fashioned hell and brimstone conservatives were on your case your water heater would have exploded or you’d have at least had a rain of frogs in your shower.

    In summary, the solution is to replace your hot water heater with one that is compliant with the laws of thermodynamics. Or you could try wrapping some leather around your hot water heater, maybe some steaks? Liberals hate meat products. Make it pork, then you’ll ward off Muslim and Jewish hate too. Three for the price of one.Report

  8. Avatar Mad Rocket Scientist says:

    check this:


    Last time I had a hot water heater behave like that, that internal tank had failed and water was flooding into the insulated space between the shell & the tank. I had to get a new heater.Report

    • Avatar Road Scholar in reply to Mad Rocket Scientist says:

      This sounds like the most likely problem to me as well. It at least explains the symptoms and is consistent with the age of the thing.

      Pop a new one in there. It’ll work a lot better than this one did before it broke and likely use less gas to boot. You’ll wish you’d done it years ago.Report

  9. Avatar Saul Degraw says:

    Has Dr. Zoydberg been to your house recently?Report

  10. Avatar ian351c says:

    The tank itself has–or should have–an inlet pipe that reaches nearly the button of the interior of the tank...

    That could be your problem. Sometimes (especially in tanks manufactured in the mid to late 90s) those inlet tubes were made of plastic that would become brittle with exposure to hot water and break off. Often into little pieces. This leaves you with all the cold water from the inlet being dumped into the tank at the top, where it is promptly siphoned off by the outlet. Usually the water will be hot (if you’re the first one to use it in the morning, say) for a few minutes, but will quickly become tepid or cold (depending on inlet temp) and stay that way until no one uses it for a while, allowing the entire tank to heat up.Report

    • Avatar James Hanley in reply to ian351c says:

      Now that sounds like a plausible explanation.Report

    • Avatar Stillwater in reply to ian351c says:


      I’ve got about 3000 square feet of lawn I wanna get on irrigation but I only have 3/4 inch line off the main at about 25 gpm at the inside tap….

      No, just kidding.Report

      • Avatar ian351c in reply to Stillwater says:

        LOL! I’m actually a professional computer nerd. The only reason I brought this is up is that I ran into it myself. I found a good site that has some great info. It’s like TV Tropes for water heaters (well, almost). http://www.waterheaterrescure.comReport

      • Avatar Mad Rocket Scientist in reply to Stillwater says:


        Do your own damn math…


      • Avatar Stillwater in reply to Stillwater says:


        Me doing my own math is like sorta like this:

        “Ok, I don’t like to gear my material to the audience but I’d like to make an exception because I was told that there is a convention of plumbers in San Francisco this week – I understand about 30 of them came down to the show tonight – so before I came out I worked-up a joke especially for the plumbers. Those of you who aren’t plumbers probably won’t get this and won’t think it’s funny, but I think those of you who are plumbers will really enjoy this…

        “This lawn supervisor was out on a sprinkler maintenance job and he started working on a Findlay sprinkler head with a Langstrom 7? gangly wrench. Just then, this little apprentice leaned over and said, “You can’t work on a Findlay sprinkler head with a Langstrom 7? wrench.” Well this infuriated the supervisor, so he went and got Volume 14 of the Kinsley manual, and he reads to him and says, “The Langstrom 7? wrench can be used with the Findlay sprocket.” Just then, the little apprentice leaned over and said, “It says sprocket not socket!”

        “Were these plumbers supposed to be here this show…?”Report

      • Avatar Mad Rocket Scientist in reply to Stillwater says:

        Oh, boy, context matters…

        Got it.Report

    • Avatar Kimmi in reply to ian351c says:

      Most of the time, the entire tank doesn’t heat up. Up to about a third of most people’s tanks is cold water.Report

    • Avatar Mad Rocket Scientist in reply to ian351c says:

      You wouldn’t need enough time to reheat the whole tank, just enough for the hot water to recirc back to the top (hot things rise, cold things sink, etc.), but that would still take a few minutes & until it did, you would have the cool or tepid water.Report

  11. Avatar Stillwater says:

    Go Ducks!Report

  12. Avatar Brandon Berg says:

    Well, I’m going to get back to work on my perpetual motion machine.Report

  13. Avatar Mike Schilling says:

    You’ve got a demand for hot water that your system is unable to meet even though none of its inputs have changed. Clearly a market failure.Report

  14. Avatar Tod Kelly says:

    Since it seems like all of the science-y possibilities have been accounted for, I’m going to go with this:

    You have sinned, and god is punishing you with cold water.Report