Marathon Storage Tanks

Discussion in 'Geothermal Heat Pump Applications' started by signal13, Sep 28, 2012.

  1. signal13

    signal13 New Member

    We are in the process of building a house and we're having two four ton Waterfurnace Geothermal units installed. The unit in the basement will be equipped with desuperheater. I am going to have a storage/buffer tank installed in series with a regular Rheem Marathon electric household water heater. What is the consensus on Marathon storage tanks assuming I can afford it? More importantly, does it make sense to buy the model that will not be energized or spend a few bucks more on the model that has backup electric element? Not sure about pros and cons. Also I noticed that the Marathon tanks come in 2 and 3 port models. How many ports would I need for my setup? Thanks in advance.
  2. geome

    geome Member Forum Leader

    The consensus is that the Marathon may not be worth the cost from strictly a water heating standpoint.

    That said, I will never buy anything else. No tank to rust, lifetime tank warranty, great insulation. I plan to live in our current house a LONG time.

    If I had a buffer tank, and I could only buy one Marathon, I'd use the Marathon as the finishing tank (not the buffer tank.) Let the 120-130°F water temperature be maintained by the better insulated tank.

    Our Marathon is the standard water heater version with no additional ports. We have two desuperheaters running to it via a plumbing "T". We don't need the additional ports.
  3. jrh

    jrh Member

    Last time I priced them the storage tanks were more $, not less.
  4. signal13

    signal13 New Member

    I priced the water heaters and the storage tanks:

    85 gallon marathon water heater: $999

    85 gallon marathon storage tank $1115

    I think I may just bite the bullet and buy them both but I'm still not sure on how many ports to get. Will I be ok if I just buy the two port storage tank? I am purchasing the tank out of pocket and my builder is going to install. I am a newbie to all of this and I just don't want to buy the wrong one and regret not having the extra port (If I even need it) Thanks for the feedback so far.
  5. jrh

    jrh Member

    You don't need any extra ports. You only need the standard hot and cold ports that come with every water heater.
  6. geome

    geome Member Forum Leader

    I agree. There is a good diagram of the piping that Bergy has posted here many times.
  7. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    A "storage tank" can be an orange or blue store electric water heater that is not wired. ~$350.00
  8. other thoughts


    the "best" vs best value.

    A "cheap" ordinary water heater has fair insulation. Most people agree that standard water heaters lose 1 - 1 1/2 degrees F per hour of heat just sitting there, especially in colder weather. If that water heater, whether used as a primary (#1) or secondary (#2) tank, is located indoors in what is called a conditioned space, you can also add an extra blanket of insulation and reduce heat loss further. To me that seems a lot less than $900.00.

    This is specifically NOT RECOMMENDED on traditional water heaters that are located outdoors. (outdoors the extra blanket insulation causes mosture to collect on the inside cheap steel outer housing and rust through)

    I originally set up my #1 preheater tank directly on bricks over concrete. (Sometimes that is useful because otherwise the drain valve can be so low as to be almost unusable)

    I then realised that heat was transferring off of the bottom of that hot water tank so I foamed in as much foam as I could to reduce (bottom) heater to concrete floor loss.
    (Think of what the loss is if the heater is sitting directly on concrete)

    I haven't tried this, but I have thought about making a foam ring 3" high (or possibly using an aluminum overflow pan). You would have a round circle about the same diameter as the water heater. You would foam it, let it cure for 3 or 4 days until it becomes hard and then set the water heater on it. Part of the water heater would sink a bit when the heater is filled up with water, but it would only sink so far. You might then pipe it allowing for another 3/8" for long term settling. I'm thinking it probably would work fairly well.

    Now you could also use any highly foamed steel tank to accomplish the same thing, but standard water heaters are fairly cheap. The ideal would be a steel tank completely covered with 3 or 4" of foamed insulation containing all the standard pipe fittings of a standard water heater. THAT could be used with anything including solar.
  9. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    My 80 gal conventional 12 year water heater loses about 1 degree every 4 hours. That's 115*F water in a 70-75*F room

    Both my finish and preheat tanks (identical 80 gal GE 12 year models) now sit on 1" blueboard, an addition I made 2 years ago upon realizing tank bottom insulation isn't much since conventional electric tank elements don't heat the bottom few inches. Both my tanks are heated externally with hot water returned via drain fitting, so tank bottom insulation is relevant.

    While I wish I'd gone with dual Marathon 105s for my setup, the delta $ wouldn't be half recovered even if both the tanks and I live to be 100.

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