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myrealnameismama_goose

In-line water heater--ruptured copper tubing

This morning as I was baking bread, preparing for a houseful of dinner guests, I heard a 'pop' under the counter, and saw the over-sink light fixture flicker, at the same time that I turned on the HW on the main sink faucet. When I checked the electric in-line water heater, there was water spewing from one side.

After turning off the supply line, cutting the power, and using every dry towel in the house, I pulled the unit off the wall, and hooked up an extra supply line between it and the cold water on the main sink faucet. I found a rupture in the copper tubing inside the unit, just above where the hot water line connects. I'm assuming that is not an easy repair. Fortunately, we left the pipe from the hot water tank that services the rest of the house, in case the in-line unit ever malfunctioned.

The heater is a PowerStar/BBT/Bosch that was installed in 2010, used only for the main kitchen sink and the auxiliary/prep sink. It is on a dedicated 220v circuit.

Does anyone have experience with this problem, or have any idea why this happened? I googled 'in-line water heater burst tubing', but mostly what I found was info on problems with lines outside the unit (pex tubing), or problems during freezing temperatures, neither of which applies.

Thank you.

Edited to add: I called Bosch this morning. The heat exchanger is still under warranty, so they are sending a new unit. I am very happy with their customer service; I wasn't put on hold, and all I had to do was upload a picture. The technician could offer no explanation for the tubing failure.

This post was edited by mama_goose on Mon, Sep 15, 14 at 11:26

Comments (9)

  • randy427
    9 years ago

    Hard to say without looking at the failure. Possibly a fitting was over-torqued, or tightened improperly, causing a pinch and weak spot in the tubing. Does the tubing appear to be twisted or otherwise deformed?

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Tubing is not twisted or deformed. I can feel a split, maybe 4mm wide, on the back side of the loop, not at a weld or seam. Due to the location, I can't get a picture, without dismantling it. On the plastic housing there's a dark spot--looks as if it might be from a flash.

    Bosch is sending a new unit, but the tech couldn't offer an explanation for the failure. Makes me a little nervous about the replacement, though. After the new one arrives, I'll take the old one apart and post a pic.

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Well, here's a picture of the back of the heat exchanger loop. What I thought was a split is really a hole--it appears that the copper corroded, weakened, and finally gave out. I think in my OP I wasn't clear on the location of the split. The hole is close to the hot water outlet, but not on the connection. In the pic you can see the hot water outlet at the bottom left.

    There has been nothing in contact with that spot, so I don't know what could have caused the corrosion. On the other side of the brass fitting is some powdery white residue, where the wires connect. I'll post that pic in the next message.

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Other side of brass fitting/hot water outlet:

  • pprioroh
    9 years ago

    Wow that is scary. lucky you were there or could have been DISASTER! No way copper should corrode in that amount of time. Was/Is there anything stored under the sink that is acidic or could be in close proximity and causing corrosion?

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Nothing. The heater was mounted in a cabinet, under a sink that isn't used often, and usually I'm the only one that opens the cabinet doors. I keep a bottle of marble polish, some scrap pieces of tile, and some small tools in the cabinet. Nothing was in contact with the heater housing, and until this incident, no leaks under the sink.

    Nothing was in contact with the copper--I could easily push my finger between it and the housing. Because the ceiling light flickered at the same time, I was wondering if an electrical surge/short could do this kind of damage?

  • pprioroh
    9 years ago

    It definitely could and in fact the discoloration around that area and the pattern of the hole looked to me like an electrical arc pattern more than a pressure leak/blow from the inside.

    It just doesn't make any sense that that copper would fail with a "pop" in such short time after installation.

    I'm no expert, but the walls of the copper around that area look normal thickness and if it was a burst from internal pressure I would think the pattern seen would be more outward and (from what I've seen in past) linear, not in a clean arc like that.

    Fascinating. Hopefully others with more expertise will chime in and I'd have the whole unit looked at personally before I'd trust it - if there is something wrong with the copper the same thing could happen in your wall or somewhere else. If there's something wrong with the electrical wiring or unit itself, that could kill someone.

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Would the arc have come from where the wires are attached to the brass fitting or the thermal cut-out? In the following picture, the thermal cut-out is mounted on the front loop of the heat exchanger. The hole is on the back side of the back loop, where there is a dark band on the copper. There's a corresponding dull spot on the black paint of the housing--is that also indicative of an electrical arc?

  • mama goose_gw zn6OH
    Original Author
    9 years ago

    Update:

    The replacement is installed and working. It's wonderful to have hot water in the kitchen again, although I'm still a little nervous about the chance of another failure/flood.

    I had the old unit checked--was told that a heating element burned out, causing the arcing. The safety cut-out on the unit worked as it was supposed to, which is why the breaker wasn't tripped.

    I asked if I should install a floor drain under the cabinet (easily drained to a sump pump under that part of the house), but was told that another heating element failure was unlikely, so not worth the trouble. I hope he was right!

    Thank you, randy427 and pprioroh, for your responses and advice.

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