Running out ot hot water w Marathon WH

bowyer123March 23, 2013

I just moved to a new home. We installed one 105 gallon Marathon water heater. Twice now we have run out of hot water. Today it was on the 4th consecutive shower and after a light load of laundry. I know that is a lot of usage, but they were all short showers 5-8 minutes if I had to guess.

Our previous home hat 2, 50 gallon gas water heaters and I don't ever recall running out of water. Our shower heads are Delta, and Brizo, not sure of the gpm flow, but they are standard sizes.

Originally our WH was producing very HOT water, so we turned the temp down to 125' from 140'.

I have a large family of 5 girls/women plus me, so hot water issues are not good when everyone wants to get ready at the same time. I heard some not-so-nice words from my wife in the shower when the hot water ran out while there was conditioner in her hair.

Any suggestions, or are we just going to have this issue forever? If necessary and feasible, I may have to add another HWH, but I really can't imagine needing so many gallons, especially considering we have had 2 50's for the last 10 years without issues.

Thanks for any insight you may have.

This post was edited by bowyer123 on Sat, Mar 23, 13 at 18:27

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Water consumption increase as younger females age into the teen years.

    Bookmark   March 24, 2013 at 10:50AM
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I have a large house, a large family and two gas heaters (slightly smaller in total than your 105). The reality is that there isn't enough hot water for everyone to take showers one after the other or all at the same time. I'm not changing anything, it's easy enough to deal with.

First thing for you to do is to turn back up the temp (135 is safer than 140). If you can't get showers staggered a bit, you need another tank. There are few homes with enough hot water capacity to serve so many showers or baths in a short period of time. And, frankly, having that much capacity for just an occasional need seems wasteful to me.

    Bookmark   March 24, 2013 at 12:46PM
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I had a few more thoughts if this is an electric heater. If not, please ignore the remainder of this post.

I read somewhere in the recent past, maybe this forum, that the "bottom" heating coil in an electric water heater is not at the bottom but is maybe 10-15 percent of the tank's height up from the bottom. If so, you're starting out with perhaps 90 gal hot and 15 gal cold in a 105 gal tank.

Also, water heaters have a spec called "recovery rate". It's how many more gallons of hot water can be produced each hour from cold water. A gas water heater typically can recover about 1 gal per hour per thousand btus. So, a 40000 btu 50 gal tank would recover perhaps 40 gal per hour, and so could supply 50 + 40 = 90 in the first hour.

Electric water heaters have very slow recovery, what's listed for the Marathon electric is 17-20 gal per hour and total supply of 104 gallons for the first hour. Compare this 104 to 90 x 2= 180 (from two gas 50 gal tanks) and you'll see that yes, you have much less hot water now than before.

    Bookmark   March 24, 2013 at 8:11PM
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