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DE-Lime water heater

krobe_2 Member Posts: 4
How successful is de-liming a commercial water heater?  This is an A O Smith 69 gallon tank 360MBTU instantaneous nat gas water heater supplying motel rooms.

The rumbling just started this season (motel shuts down for the Winter).

Is disturbing the adjacent rooms.  Need to get through the end of October.

Have tried 2- 45 minute applications of flow-aide which did not help.

Am trying to locate some Un-lime from AO Smith.

Thanks, Mark K


  • Larry Weingarten
    Larry Weingarten Member Posts: 2,293
    Do you have...

    ... access to the clean out hatch, or is it right up against a wall?!

    Yours,  Larry
  • krobe_2
    krobe_2 Member Posts: 4
    Cleanout not an option

    Clean out cover is accessible but substantial rust on plate and bolts.  Not an option to remove it at this time. 

       We did another treatment of flow-aide.  3 gallons for 1 3/4 hours, flush out; same process a 2nd time.  Some brown sand-like residue was flushed out.  Also lowered the temp down to 120.  The rumbling and popping still occurs the longer the burner fires, but not as loud as before.  Has anyone had any success de-liming a water heater?
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,293

    Hello:  I'd look into getting a new plate, bolts and gasket as that access will give you the best chance at a quiet heater.  One thing you can do in the meantime is to derate the main burner a touch.  This will quiet things down, but you can only turn it down to the point just before guest complaints start to come in. 

    A wet/dry shop vac hooked up to a 1" copper pipe can pull out a lot of sediment once the hatch is available.  If anyone in your area has a Muck-Vac, it is a tool I used to make that can clean out sediment from the top ports on the heater.

    Yours,  Larry
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669

    Are you sure that it is not just sand built up in the bottom ot the tank.

    Pull the clean out and empty the junk out.
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