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Bock Indirect Trouble

Plumdog_2 Member Posts: 873
Put in an 80 gal. Bock Indirect about 3-4 years ago, and it seems clogged up; like something is blocking the flow of water thru it. I'm talking about the storage tank itself, not the coil. The water gets hot but barely flows out the hot port (and it's a big inch and a halfer). No obtructions in the cold inlet or hot outlet. Anybody ever experience this? Going to look in there with a scope in day or so...customer getting angry. Could the coil get so scaled it would block flow thru the tank? 


  • hot_rod
    hot_rod Member Posts: 22,254
    It would take a bunch

    of sediment to plug up all of those coils. They are smooth coils, no finds and there is a lot of space between the coils. And the coils are fairly tall in the tank.

    I believe the coils are not removable but welded into the tank.

    Are you sure the blockage isn't upstream somewhere before the tank, a partially opened ball valve or something?

    Maybe disconnect the cold line and flow it into a bucket for a flow rate check.

    If it is plugged that bad better look into some water treatment.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    I thought the coil had fins.

    One of our people put a direct bypass around the heater and with that, the flow is equal hot and cold. Almost acts like something floats up into the outlet and partly plugs it, the flow is there for 5 seconds or so. I took the mix valve out of line. Nothing to stop the flow but the tank itself.
  • icesailor
    icesailor Member Posts: 7,265
    Bock Indirect:

    I'm not familiar with that tank but are you saying that the boiler side of the coil is in the tank which is filled with boiler water, and the domestic hot water comes out of the coil? That's strange. The only water heaters I ever saw were high output units that were actually hot water boilers with a big tankless on the side. All the domestic hot water went through the coil and the burner heated the water in the tank.

    If your tank isn't like so, and the cold goes in one side of the top and the hot goes out the top also, the tank is the tank. If this is so, the dip tube is failing or is plugged. There are usually dialectic nipples that go in the tank. They are plastic lined and rust will get between the plastic and metal of the nipple causing it to swell and causing the obstruction. Is the nipple sticking out the top of the tank, galvanized? Is there a fitting adapter screwed to this nipple and the next fitting was soldered on and there is no way it was installed without soldering next to the nipple? They tell you for a reason, not to solder next to that fitting. You probably didn't do it but I've seen it done. Lots.
  • icesailor
    icesailor Member Posts: 7,265


    If the Bock indirect is the one listed here:


    and the domestic hot water is connected to the side outlets i is connected WRONG. See those white parts inside the nipples, if you heat the adapter while soldering in the coppr nipple, you will wreck it. the connections for the boiler.

    If it isn't so and boiler water goes in the coil, and the domestic water goes in the top of the heater, the dip tube is failing. Or the plastic in the cold and hot nipple is swollen.

    has anyone seen any small bits of white plastic in the faucet strainers or failed solenoid valves? That's a sure sign of a failing Bock water heater. The tank will be next.
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