Living on borrowed time

The Tank Living on borrowed time

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    Existing tanks details:

    40 gal, 34K btu, 34 gal recover, 70 gal 1st hr.

    50 gal, 40k btu, 42 gal recover, 82 gal 1st hr.

    I have 40 and 50 gallon tanks in series supplying our home (2 adults, 2 teenage daughters and one pre-teen boy). The 40 gallon tank has the cold water supply and is the oldest at 20 years. I have no problem with hot water supply during the summer months. But as the incoming water temp goes down during the winter (to 36 degrees), the two tanks really struggle to keep up. I can easily run out of hot water in our master bathroom shower alone in 10 to 12 minutes in the dead of winter. Granted, it is a high draw shower with two shower heads and 4 body jets (8 GPM). But it should last longer than that, right? Add the teenage daughters to the equation and we are out of hot water quickly some mornings.

    I have turned both thermostats up to high and it did not help.

    My goal: make it last longer (at least 20 minutes).

    Neither tank leaks, but my gut tells me that the 20 year-old tank has lasted longer than expected and I am on borrowed time. I imagine they are both very inefficient units.

    I looked at replacing them with a tankless unit, but with the incomming cold water being an amazing 36 degrees and three showers running sometimes, I dismissed that idea quickly.

    Question: If put a 65 or 75 gallon high recovery unit in place of the 20 year-old 40 gal unit, does anyone foresee a problem since it would be feeding a 50 gallon tank that is 9 years old. Will adding a larger tank in place of just the old 40 gal unit help or would a buying two new 40 and 50 gallon high recover tanks be better since they would be more efficent and have better recovery time?

    Any comments, suggestion or ideas are welcome.

    Larry Weingarten

    Hello: Your choices basically are add more hot water generating capacity or reduce usage, or some combination. Understand that you will get about 75% of the volume of the tanks as undiluted hot water. Actually I’m surprised you even get 10 to 12 minutes with six shower heads running. My quick calculation showed about eight minutes. I’d start by finding a way to use only the shower heads that are needed. Put shut off valves on the body sprays for instance and use them when there isn’t a lineup wanting to shower. A really innovative solution to your problem might be to install a GFX shower heat exchanger They can capture up to 60% of the lost heat so would essentially double available shower time.

    Once you have taken measures to use only what’s needed, you can size heaters to suit.

    Yours, Larry

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