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Periodic Maintenance on a 16 year old HTP DWH - Y or N?

jdbs3 Member Posts: 32
Recently purchased a new home that has a Bosch Greenstar residential gas condensing boiler, and an HTP DWH Model SSU-45 (indirect fired). Planning to have a local HVAC company service the one year old Bosch gas boiler soon.

However, the HTP DWH is 16 years old and was (probably) never serviced. The installation manual list the yearly maintenance that should have been done, including:

. Checking the relief valve by lifting and releasing the valve to assure it is working properly.
. Checking the drain valve by opening the drain and draining some water.
. Testing all functions of the system.

In conversation with HTP, they also recommend that every 5 years, the technician perform a ‘shock coil treatment’ to brake loose any mineral build-up on the exterior of the indirect heating coils. And since the DWH has never been serviced, this also be done.

BUT the system is 16 years old, and never serviced. What are folks thoughts on whether this yearly maintenance should now be started? A visual inspection makes sense, but I am concerned that doing anything more might just open up a ‘can of worms’, and possibly result in needing to replace components, or even replace the entire DWH.

All thoughts are appreciated.


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,331
    Hi, Your tank is 316-l stainless, which holds up nicely in decent water. I suppose a question to ask is if it leaked, would that damage things? Most tanks start with a slow leak, which would give you time to find a replacement.
    The conditions the tank lives with, like water pressure, water quality, amount of hot water use, and how hot it's kept have a lot to do with how long the tank lasts. So, if those things are not too far out there, I'd just keep using this tank. I suppose you could find a replacement and keep it on hand, but not install it till the current one fails.
    Just for a different perspective, if it were a glass lined tank, you could keep it going a very long time with regular anode replacement. I've gotten over fifty years from glass lined tanks.

    Yours, Larry
  • tim smith
    tim smith Member Posts: 2,765
    Turn boiler off and cool down the tank to cold water temp, run hot tap till cold. Then turn boiler back on and measure inlet and outlet temps to heat x of tank after appx 20 min running with good strap on differential thermometer. With diff of temp on coil we should have pretty good idea of if heat x is fouled once boiler and indirect size are known. Unknown will be flow rate but should be able to get close enough.
  • HomerJSmith
    HomerJSmith Member Posts: 2,467
    It all depends upon the quality of water. That's why boiler water should be quality water in the sys and, also, the quality of the domestic water supply is important.

    Mineralization on the heat exchanger ocurrs because the minerals comes out of solution on hot surfaces. 1mm of mineralization on a heat exchanger reduces the heat transfer 12%.