Black Specks only in HOT WATER

Discussion in 'Water Heater Forum, Tanks' started by TTN, Aug 2, 2019.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    That valve with a grey knob is a tempering is used to set the maximum water temperature to be fed to the house. It is independent of the setting on the WH. It allows the WH to be set to a higher temperature if you wish to provide more hot water and to ensure it gets hot enough to kill anything without scalding you if you had full hot turned on somewhere by mixing in some cold to temper the output to where you set it. Where I live, one is required, and they're a good idea anywhere. WHere I live, they also require an expansion tank, and they can be a good idea, depending on what the supply system has in it.

    A check valve prevents water from the house pushing back into the supply line, and potentially polluting the water in the neighborhood. Worst case scenario...your hose is sitting in a puddle in the yard and there's a hiccup in the pressure sucking in dog poop, insecticides, and maybe fertilizer when they open up a fire hydrant down the street to fight a fire, dropping the pressure. Yes, it's not a common situation, but it can and has happened...a working check valve will prevent that, but also means when the WH operates, there's no place for that larger volume of water to go unless you have an expansion tank. The pressure spikes almost immediately since the water is not compressible nor are the pipes very elastic. The bladder in the ET can compress easily, and absorb that expanding water without spiking the pressure.

    Without some plastic/rubber lined hoses somewhere in the hot lines, can't think of any common sources of black specs that aren't also in the cold lines (i.e., exclusive to the hot supply), especially when they are at all outlets. It obviously has to be in some common line unique to the hot supply. I don't know of any WH that has rubber components inside of them, but then, I've not taken any apart. Haven't heard of anyone reporting them coming from inside of the WH.

    If they were hard, like grains of sand, it could be some precipitate created by heating the water, but I think you implied they were oily, which implies rubber/plastic as the source.
  2. TTN

    TTN New Member

    Aug 2, 2019
    Fort Worth, Texas
    Hello All!! It looks like the new plumber was able to fix the issue!!! The culprits appear to be the "Dielectric Nipples" which are connected between the hot water heater and the flex hose!!!! Please see picture at how they look almost burnt.... The rubber valves inside this part was disintegrating.

    I do have a final question. Do the Dielectric nipples come with a new hot water heater? Or is it a part that you buy separately for the install? My hot water heater was replaced in January, how could the dielectric nipples look so burnt and rusted?

    Attached Files:

  3. phog

    phog Active Member

    Jul 29, 2017
    Rochester NY
    A couple things to unpack in your question.

    1. Typically, almost all new water heaters have dielectric couplings built in to their water connections. External dielectric nipples are not needed in this case. However to have "extra" dielectric connections in the system doesn't hurt anything. So the person who installed your water heater probably left old, previously existing nipples in place.

    2. Dielectric nipples don't have a valve, they are just straight-through pipe nipples with a plastic lining. Your picture doesn't show a view down through the inside of the nipples, so it's hard to know for sure, but what you may have there are what is known as a heat trap nipple. Which has a little valve that prevents convection circulation of hot water from inside the tank up through the hot/cold pipes while in standby. Some, but not all, new water heaters have built-in heat traps.

    3. If your next question is, "do I need those heat traps?".. To have a system without heat traps is slightly less efficient, because hot water can circulate up through the pipes and lose extra heat to the environment. The efficiency hit is not large cost, perhaps in the low tens of dollars a year for the typical home. But it is a loss that adds cost over time. Integral heat traps / heat trap nipples are also not the only way to prevent convection losses-- another way is to simply have the pipes loop downward after they exit the water tank so that convection is not possible.

    Anyway I'm glad you found your problem.
  4. WorthFlorida

    WorthFlorida When the wife won't let you get a Harley!

    Oct 28, 2009
    Orlando, Florida
    It sounds like no one ever used sweated copper fittings. Some will solder the fittings while attached to the nipples and could burn them up.
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