oversized water heater

mrspeeder

Hi, My mother has a 1 family house. A few years back my father installed a 200 or 250 gallon AO smith gas water heater. The plan was to convert the house to a 2 family. Currently there are only 3 people living in the house and the gas bill is through the roof. I lowered the temperature on the water heater but it's not that hot now. I am not sure how to make this water heater efficient it's definitely oversized for the house. The only thing I can think of is to put in a tankless water heater.

Any suggestions would be great.

Thanks!

EdTheHeaterMan

A 40 gallon water heater is sufficient for 3 people. How old is the large commercial heater?

Can you sell the AO Smith Commercial on the internet? They are not cheep so you can get a couple of hundred for a used one if it is not too old. Remember you paid retail for the tank and the installers, You are not gong to get anywhere neat what you paid for it. You will be selling at less than wholesale cost and the buyer needs to pick it up. Not like getting a new one delivered by the supply house.

ethicalpaul

The only thing I can think of is to put in a tankless water heater.

Why haven't you thought of taking the monster tank offline and installing a 40 or 50 gallon gas or heat pump water heater? Not judging, just wondering if there's some reason

Looking at how much a 250 gallon AO Smith water heater costs, you could probably sell it and pay for many years of hot water.

Intplm.

Suggestion…Replace the water heater with a properly sized water heater that will accommodate the needs of the occupants.

jesmed1

Just for reference, we have a 75 gallon gas water heater in a 4-unit condo building with 4 bathrooms and 6-8 occupants, and we've never run out of hot water.

As others have pointed out, 200 gallons for a 2-family is massive overkill.

Grallert

Simply drain it and take it of line or add it in series before a properly sized water heater. We have a BTHL-250 servicing 25 teenaged girls and two families including a full four washer laundry room. That's a pretty big water heater lol.

hot_rod

250 if a very large tank, depending on the burner size it may be an ASME tank, worth some $$$ depending on the age

How is it vented.

Larry Weingarten

Hi, A forty gallon gas or fifty gallon HP would cover the need unless there is a ten gpm showerhead 🙀 A question is what else is using gas? Has the system been checked for leaks?
Yours, Larry

ps, I've also had water leaks keep a gas heater firing up. So have a look at your water meter when no water is being used.

pecmsg

https://forum.heatinghelp.com/discussion/200906/oversized-water-heater

water heaters need to run at 140* to kill the legionella bacteria. Then a mixing valve to limit the water temp to 110-120* max.
just get a smaller heater.

mattmia2

i would be less concerned in a reasonably sized water heater but with all that water that is going to sit for days or longer it needs to be hot enough to sanitize the water.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1847873#Comment_1847873

my WH was set at factory at 120F and it warns me of scald danger if I even bump it to 130F so I think the lawyers at Rheem at least think 140 isn’t necessary

pecmsg

https://forum.heatinghelp.com/discussion/comment/1847890#Comment_1847890

Legionella Temperature Chart Explained: 4 Crucial Temperatures to Prevent Risk - Prevent Legionnaires

hot_rod

it is a tough call, legionella, or scald litigation.

Elevating the tank temperature and mixing down is one option, or a chemical romance.

It comes down to your risk aversion, in some places cold water lines can harbor legionella. Piping run through attics in hot locations, for example. Now what?
That is one argument for a chemical solution.

Larry Weingarten

Hi, To complicate things, the age and condition of the occupants and potential visitors needs to be factored in. For a nursing home, absolutely heat to 140F and mix it down. For healthy adults, I like 130F as something they can deal with. I always ask about and try to get people to pay attention to the water temperature and things like fluctuating temps in the shower. Part of our job is to educate.
Yours, Larry

mattmia2

https://forum.heatinghelp.com/discussion/comment/1847911#Comment_1847911

In a 40 or 50 gallon tank where the municipal water with residual disinfectant gets replaced daily is much less of a concern than a 200 gallon tank where maybe 1/4 of it gets replaced daily so the disinfectant concentration will be much less as it sits and degrades. Of course if the occupants don't bathe daily or are out of town a lot then the same concerns exist with the smaller tanks.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1847893#Comment_1847893

Tell Rheem, not me 😅

But seriously, that document skips over the 122 range where it does kill it, it just takes longer.

I will also say that every year about 8,000 - 18,000 people in the US are hospitalized from Legionnaires from household plumbing (these are estimates because it's difficult to say exactly the source).

33,000 people in the US are hospitalized due to bathroom slip and fall accidents every year so I hope we can all chill a little bit with the heavy legionnaires concern in the home.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1847943#Comment_1847943

Legionella protection makes sense in cases of hospitals, retirement homes, places where people are ill opr have compromised immune systems.

Every home in America??? I suppose it like buying insurance, what type of policy, how much coverage, etc, etc.

The mixing valve is a simple inexpensive solution, and it extends your WH output.

I think tank life is shortened with higher operating condition, more mineral precipitation.

Pros and cons

mattmia2

The reaction that corrodes the tank happens faster at higher temps too.

There are pretty definitive ways to kill legionella. There are thousands or more sources of falling.

Hot_water_fan

you could replace it with a smaller tank. That said, it’s winter. The high gas bills are probably unrelated to the water heater. What was the gas bill in August? I suspect replacing the heater would be a net cost and a bad use of their time and money.

hot_rod

Of course if it is a condensing A O Smith Cyclone, it could be pretty efficient :) And worth more than my truck!