black bits in hot water: HELP ME!

The Tank black bits in hot water: HELP ME!

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    I know what you’re thinking: braided lines. But no, I have NO braided lines. I have 2 Lochinvar water heaters, about 7.5 years old, anode rods replaced about a year ago (when I first started tackling this black bit thing. Didn’t help, so I gave up in frustration, but am ready for round 2 now). We are having a problem with sediment. Draining the tanks provides me with LOTS of black stuff, large pepper ground size (approx) and turquoise bits. Black doesn’t dissolve in vinegar (read somewhere that that was a test for something… Can’t remember what now).

    This is a real problem as the bits float through the house and constantly clog up the hot water flow, especially in single-handle showers, where we now can’t run more than one hot thing at once, or the shower pressure drops to nothing.

    We are on city water. None of the neighbors have this problem.

    We were using a recirculator, but I stopped using it because I thought it would only help send the bits around the house (it draws from the bottom of the tank).

    Baths are gross: turquoise water with black bits. Worse in the larger tub on the lower floor.

    Have drained tanks for several hours, still getting junk out (flushing by turning off and on main supply). Smaller tank is clogged; I was able to unclog it twice by stuffing a wire up the drain, tons of black junk came out, but now can’t get it unclogged again.

    I’m too frustrated. Any help trying to
    1. Figure out what the heck this stuff is
    2. What to do to get rid of it

    would be WONDERFUL!!!

    Larry Weingarten

    Hello: I’d like to know everything that’s in the water system, but as a start, put a spring loaded check valve on the recirc line and set it up for flushing.

    Doing this means coming out of the tank port where the drain would be with a lined steel nipple, brass ball valve, brass nipple, brass “T”, out other end of “T” with brass nipple, ball valve and hose adapter. Coming out the center of the “T” should be brass nipple, spring check, brass nipple, ball valve, brass nipple to pump and on. Or you might want to put that last ball valve on the other side of the pump.

    Yes, I know, a picture would be better 😉

    This setup will allow you to flush out tank and piping separately and will keep yucky stuff on the bottom of the tank from getting into the plumbing in the first place.

    Yours , Larry


    Thanks, Larry. Why a check valve? I thought check valves were to prevent backflow. The water exits at the bottom of the tank, so the check valve would only serve to prevent backflow into the bottom of the water heater. Is that what you mean to say?

    If I understand you correctly, I should install both a check and a ball valve on the recirc line.. Is that right?

    Unfortunately, this won’t solve the issue of the gunk circulating through the system even when I’m not flushing it, I don’t think. Plus, I’d like to get rid of the stuff — it obviously affects the performance of the heater and takes up space that could hold hot water… Any ideas on that front?

    Larry Weingarten

    Hello: The pump pushes slightly cooled water back into the bottom of the tank and does so with maybe five psi that a pump can develop. When you draw water a much greater difference in pressure can develop, pulling water from the top of the tank but also from the bottom, even if the pump is running. That’s why a spring check is needed. A swing check can get stuck in the open position.

    Most of the gunk is on the bottom of the tank and the recirc line gives it direct access to the piping. Flushing the tank is good, but better to keep the stuff trapped in the tank than to let it roam free in the piping. The ball valves are to give you control over the system so you can flush it and the tank effectively. This will solve the problem of gunk that’s heavier than water getting into the system.

    So, what else is in the system? Is there or has there ever been a softener? The gunk could be zeolite resin from a broken softener. Or, does the stuff smear on fixtures? More info would make my guesses better 😉

    Yours, Larry

    ps. The pump has an arrow on it. It should be pointing towards the bottom of the tank. If not, that’s a big part of the problem.


    Copper and chlorine? Please check my post in Tanklets, Black Particles in Hot Water.


    Randy Schuyler

    There IS a diagram of Larry’s setup, more or less, and taken from his own book. Go to

    Randy Schuyler


    Thanks, Larry. No water softener, never was (we are first owners). System is 2 water heaters, copper pipes, lots of single handle (mostly Delta) faucets in baths and showers and kitchen. There is a small amount of black goop that is somewhat slimy (see it in the bottom of the bucket pic), but the majority is non-smeary black bits mixed with turquoise bits. The bits are actually kind of rough to handle — they have irritated my skin when I’ve been wiping them up. Feels like little paper cuts…

    So the check valve is to prevent flow from the bottom of the tank to the recirc pump? I don’t know why, but for some reason I was thinking the pump pulled from the tank, rather than pushed into the tank…

    Randy, I can’t get that link to work… Will try to find the page manually. Thanks for the info.

    David, how would I test/know if the source is copper and chlorine? Is the copper coming from the copper pipes? If so, why don’t the neighbors have the same problem (they have the same city water, and copper pipes)?

    Thank you all for the help!!


    Darn, photo didn’t load! Will resize and try again!


    These are some of the bits that I managed to spray around the shower while draining the tank…

    Attached files


    This is some of the various bits and gunks that have come out of the heaters.

    Attached files

    Randy Schuyler

    Try this:

    I couldn’t get it to work either, but I noticed that the link included a period at the end.

    I think you should take that last photo and frame it. It looks like art to me.:cool:

    Randy Schuyler


    Grasping for straws here. When problems occur, one of the first questions is “What has changed?”. It seems the anodes were changed but does that alone explain the symptoms?

    Do the black particles stick to a magnet? My understanding is the Navy will inject oxygen into the primary coolant system aboard nuclear carriers and subs when first commissioned. At room temperature iron and oxygen produce red rust, Fe2O3, which does not bond to the substrate but falls off, exposing more surface to rust. But at higher temperatures, you get Fe3O4, magnatite, which is black rust. This bonds to the substrate and prevents further rusting. I think pressurized water reactors operate the primary loop at about 550F and 1600 psi+. The boiling water reactors I worked at operated at 546F and 1005 psig.

    You only hear about WHs rusting out and red rust. Do you have the right temperature and water chemistry to create magnatite? Who knows? Most oxides are brittle compared to metals. As a WH experiences temperature/pressure changes the steel which flex ever so slightly (but not yield). Any oxide would not flex; the oxide to metal bond would fail and the oxide fall to the bottom of the WH.

    When copper dissolves in acidic water, you usually only get turquoise stains, not particles.

    Try a magnet on both the black and green particles and get back to us.



    No, not metallic, even with a rare earth magnet.

    I changed out the anode rods after the black particles appeared (that was the first suggestion that was made at the time — that the anode rod was decaying). So the new rods aren’t the cause….

    Any other ideas?…


    Randy, I thought the photo looked like those sand art things you can buy at science museums! 😉

    Larry Weingarten

    Hello: Just a couple of random thoughts. The blue-ish stuff is corrosion from an aluminum anode. Now, was any work going on with water mains in the street? That could introduce doit into the lines 😕 Sometimes it’s possible to be at the end of a main line or at a low spot and get all the gunk from the main settling into your plumbing. A water filter on the main house line would tell you, but filling a big white bucket fast from a hose bibb where water comes into the house might also give you a clue. If any if this grey grit is in the bucket, you’ve found the problem. Whatever, your water heater is a big settling tank. The recirc line is sipping on the grey matter every time water is used (or pump runs).

    Yours, Larry

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