75 gal. or 50 gal. hot water heater

10 years ago

We recently bought a house and are replacing the hot water heater before we move in. The old heater was 40 gallons, but we are trying to decide what size tank do we need. We are a family of 2 adults, 1 toddler and 1 on the way (so soon to be a family of 4, 3 of whom are females). We have 2 full bathrooms with regular bathtubs, nothing fancy; and 1 powder room. We also have a dishwasher and 1 old-fashioned washing machine that uses a lot of water. I believe all of the faucets/shower heads we bought for the house are 2.5 GPM. Both of us like to take long showers, maybe 25-30 minutes, plus there is a daily bath for the toddler, etc. We also expect visiting family sometime in the future - so the need for 4 showers within 1-2 hours - would be a necessity. I would prefer not to stand by the bathroom door with a timer and/or limiting everyone's showers to 5 minutes. We are making a lot of other energy-efficient improvements to the house, but this is one area where I think we should go with 75 gallon tank.

Any thoughts? Opinions? Your personal experiences? Did you install a 50 gallons tank that you later regretted? Did you install a 75 gallons tank and later wished you went smaller?

Featured Answer

Elmer J Fudd

10 years ago

I think you need a 75 gallon model or, if your water supply isn't too hard, a tankless heater.

With a 2.5 gpm shower head mixed at 2/3rds hot and 1/3 cold, a 50 gallon tank gives you 30 minutes of showering. At that point, you have 50 gallons of (at best) lukewarm water in the tank. You'd probably need to wait 30 minutes from that point until the water in the tank is again hot. If two are showering at once and no other hot water is being used, it'll start getting cool after about 10 minutes.

If you're using a lot of hot water, there isn't going to be that much difference in operating expenses between the two sizes, you're going to be burning BTUs to heat water either way. You can easily cover the cost difference with the savings you'd have by replacing your old washer with a front loader.

Sort by:Oldest

Comments (8)

mike_home
10 years ago
Of these two choices, I recommend getting a 50 gallon hot water heater with a 50K BTU input. This will produce 88 gallons of hot water during the first hour. You want a hot water heater that has a fast recovery. The 75 gallon hot water heater only has a 55K BTU input. It more storage but it takes longer to reheat the water.

You will be amazed how little hot water you will be using with your new faucets and shower heads. Washing machines don't use that much hot water since most clothes are washed in either warm or cold water. A dishwasher also uses little hot water. I personally set the dishwasher on the 4 hour timer so it using hot water during the middle of the night.
invisible_hand
10 years ago
I recently installed a Bradford White M-2-TW-50T6FBN - 48 Gallon, 67,000 BTU (natural gas) input for my family of 3 plus a baby.

48 Gallons is more than enough to fill a standard tub, and math says that it is enough to supply 19 minutes of pure hot water without resupply, and with a first hour delivery of 108 gallons, we could run one shower all-hot for 43 minutes.

In practice, hot water heater seems to barely run after showers are complete (reflecting reality, that much less than 2.5 gallons / minute of hot water are used, and most hot water used during the shower is being replaced during the shower.)

I am more than happy with the 48 gallon tank, but think that 67k input is likely a bit overkill for our needs (we rarely take sequential showers.)

Good luck!
Related Discussions
Do I go tankless water heater or wait for 75-gal gas heater?
Q
Comments (7)
We don't have much info to go on. We don't know what your needs are, what your wants are or what your budget is. All we really know is that you want gas in the event that the electricity is out. A tankless requires a small amount of electricity to operate - it would not operate if the power was out. A generator would solve that problem and provide power for other things as well. I don't completely agree with Dan, you can size a tankless to run more than one thing at a time. I sized mine so that in the coldest part of the year I could run the shower and the bathroom faucet - in the summer I can run about twice that amount. It works fine in my house, but if I had a larger family I'd go with a larger unit. There are also 50 gal Hybrid units - They store the water but have high BTU input and very high efficiency. They can produce a certain amount of continuous hot water as well. These meet the 30% tax credit requirements and vent with PVC pipe - making them cheap to install where long vent runs are needed. I have included an example - I'm not endorsing a particular brand. Note that these would not run without a small amount of electrical power. Here is a link that might be useful: State Hybrid
...See More
Polaris 50 gal. High Recovery Water Heater vs. 2- 50 gal. tanks
Q
Comments (3)
I just googled for the polaris water heater, and it costs $3400?!? That's nuts. Put in a 60-70 for the bedrooms and a 50 for the other and save $2500. Since you're already plumbed for two WH, the installation will also be more involved if you convert to a single. Do you know and trust this plumber? Doesn't sounds like he has your best interests in mind with that suggestion.
...See More
65 or 75 gal water heater help please
Q
Comments (4)
I'd really like to have sympathy for your situation... I'm just having a really hard time mustering it. A 70 gal "Asian soaking tub", like multi-head showers, are so wasteful it falls into the gluttonous category. You do have to think it all the way through. Don't install something like that unless you can do all of it. If you can't afford what it takes to make it work, then you can't afford the tub (or multi-head shower) It's like buying a Hummer and complaining about the price of gasoline.
...See More
Using 40gal House Water Heater w/ point of use 12KW for TUB
Q
Comments (2)
My brother in a distant State had a similar problem and his contacts had no solution to offer. So he asked me. He had a point-of-use heater in the bathroom and that was the only hot supply for his 75 gallon tub. The tub was not used often. The point-of-use heater had such a low flow rate that the first water into the tub had cooled by the time the tub was filled and the entire thing was chilly. He also had only a low crawl space under the house for adding any equipment. So I did all the calculations on the basis basis of the BTU required-- ergo, the tub required X BTU for a fill of Y gallons at temperature W. His plumber determined the largest electrical water heater he could find that would fit into the crawl space. I calculated the needed temperature for that size heater to store the required X BTU. And it turned out that it would have X BTUs at temperatures just under the maximum possible setting. So the heater was installed, becoming the only hot water supply to that tub. Power to the heater is controlled by a relay which is controlled by a wall switch in the bathroom for the occasional use. Keeping the heater hot all the time is possible if desired. He turns on the heater about 1 1/2 hours before using the tub. The heater supplies the required heat of X BTU and the cold water supply to the tub makes up the remainder of the required water volume. That's the procedure. You can do your own calculations.
...See More
Bongo
Original Author
10 years ago
The 50 gallons we are thinking about has (1) 55 gal. recovery (2) 50,000 btu and (3) 88 gal. first hour rating. The 75-gal. model has (1) 60 gal. (2) 55,000 btu and (3) 131 gallons. Does that change anything? I agree with Mike_home that we need something with fast recovery...
mike_home
10 years ago
No it doesn't change anything. The 50 gallon unit will keep you in hot water. :)
invisible_hand
10 years ago
If current hot water heater isn't failing, I would suggest waiting to replace until you've lived with the (presumably) standard input 40 gallon tank and have an idea of how well it works or doesn't work for your needs.

Your experience may well inform your decision on what you need when you replace.
fsq4cw
10 years ago
We have a 60 imperial gallon 'OSO' brand stainless steel DHW heater. It heats the water to 175F and has a mixing valve that brings the temperature down to 120F at the output when there's a demand for hot water. The advantages are that being stainless steel, it's liking going to last as long as the building is still standing, far less prone to developing Legionella that's inhaled during showering as the water is atomized and the 60gal tank at 175F is the equivalent to a standard 90 imperial gallon tank in a smaller package ( but physically still pretty large). It also came with a 15 year guarantee.

SR
Elmer J Fudd
10 years ago
If I recall correctly (the last time I looked up legionella), 140 degrees F was all that was needed. At that temperature, it tended to be a continuing problem in electric heaters (because of the cool water zone below the lower element) and not a problem at all in gas devices.

What's your thinking for using such a high setting?

75 gal. or 50 gal. hot water heater

Elmer J Fudd

Comments (8)

mike_home

invisible_hand

Related Discussions

Bongo
Original Author

mike_home

invisible_hand

fsq4cw

Elmer J Fudd

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

75 gal. or 50 gal. hot water heater

Elmer J Fudd

Comments (8)

mike_home

invisible_hand

Related Discussions

BongoOriginal Author

mike_home

invisible_hand

fsq4cw

Elmer J Fudd

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Bongo
Original Author