Replacing 75 gallon water heater

The Tank Replacing 75 gallon water heater

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    Thank you for all the incredible information on the site!

    I am needing to replace my 24 year old 75 gallon natural gas Rheem water heater (model number 21V75), which for at least the last twelve years, received no maintenance at all. Had an issue with the pilot not staying lit. Did all I could do to trouble shoot then called plumber who confirmed that the controller is bad and needs replacing. Said cost would be close to half of what a new heater would be and suggested replacing as there is some areas of rust showing up. This water heater supplies 4 shower heads, a soaking tub and 4 sinks.

    Plumber quoted AO Smith replacement heaters (doesn’t carry Rheem) and suggested either a 50 gallon (model GCF-50) or 75 gallon (FCG-75) as replacements. FCG-75 has 81 gph recovery and GCF-50 has 42 gph recovery, but has a first hour rating of 81 gallons.
    Looks like they both have brass drain valves. Both have “Coregard” anode rods that have stainless steel core that apparently extends life of the rod. They are magnesium anodes I believe, but the FCG-75 has 1 inch water connections so I am not sure I can put another anode in the hot water line. I am not able to determine where the anode is located on the FCG-75 diagram. Doesn’t show it as being on the top of the tank. Both have 6 year warranties. They both have a “Dynaclean Diffuser Dip Tube” made from pex. Would that need to be replaced with your curved tube?

    The plumber sent out on the service call was not familiar with FVIR. I was wanting to avoid Rheem since if it trips, it can’t be reset as I understand it.

    My plan was to get a basic water heater and purchase the anode and dip tube kit, but am not sure if this will work for my needs. Any suggestions as to what to go with or other manufacturers that might facilitate using two anode rods more easily?

    I guess I am in need of advice for replacing a 75 gallon heater since they don’t seem to lend themselves to best maintenance practices as described here (2nd anode, etc) as easily.

    Thanks much!

    Randy Schuyler

    My first thoughts are: do you really need a 75-gallon water heater? For that, go to, scroll to the bottom, click on Resources, and find the links to two water heater maker sizing programs, which will tell you how much you need.

    I agree that Rheem’s FVIR system is more of a problem than some of the others. It may never trip, but if it does, it will be a nuisance to get it fixed. Other possibilities for water heaters include some of A.O. Smith’s sub-brands, such as State/Kenmore and American/Whirlpool/Maytag. Those may give you some more models to choose from. With some, you might have to replace the factory aluminum anode with a magnesium one, but that’s all.

    All the makers offer self-flushing dip tubes, but we don’t think they do anything. They stir up sediment, while a dip tube actually expels it. It’s never been clear to me how a stainless steel core wire is superior. The core wire ensures electrical continuity with the tank that makes a rod of metal an anode. The anodic metal corrodes first and the core wire last. What advantage does stainless offer there? I think of self-flushing dip tubes and stainless steel core wire as features that the makers offer to make their product seem better than others’, yet which don’t cost them much, if anything, and really don’t do anything.

    Randy Schuyler

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