tankless water heater

Salty

Salty

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Salty
  • Just two of us in the house usually, with a spare bedroom for 2 or 3 more on rare occasions
  • Very rarely are two showers used at once
  • large garden tub - close to 100 gallons
I don't want to buy a huge water heater, because 330 days out of the year the 50 gallon one I just installed last year is overkill already. But, once or twice a month the wife wants to use the tub, and that's the issue. The 50 gallons doesn't fill the tub enough.

I'm thinking of throwing a small tankless heater in series after the existing tank heater and set it at a bit lower temperature than the tank. Then, it will never turn on unless we drain the tank heater and it will kick in to finish filling the tub. Since it will only run one faucet, it can be a smallish one.

Good / bad idea?
 
If you are gonna do it, just yank the 50 and be done with it. The difference in cost will be minimal.
 
Salty said:
Good / bad idea?
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Gas or electric?

Had same problem. But house all electric. Price and load for tankless rather stout. Plumber buddy recommended adding conventional 30/40 gal water heater inline before 50 gal. When needed hit breaker on 1st heater and 30 min later have plenty hot water for jacuzzi tub or when have company or grandkids. Turn off when not needed. Total cost was much cheaper. Plus have backup if 50 gal fails... which it did. Went with 40 gal as it was cheaper than 30 gal. Gas tankless would have been different.
 
frfly172 said:
Have a gas tankless ,not crazy about it .
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We’ve had our gas tankless for 10 years now. Glad we put one in. Had only one problem in that time when the igniter went bad. Five of us in the house and it does just fine.

Rather than put one in line I’d also replace your existing heater and be done with it.
 
Think it wastes a good deal of water ,getting to the point of use,and if you turn it off for a few seconds ,you have to wait for it to go through all the pipes to get hot again.
 
It’s probably been 20 years ago, and technology may have improved, but I put in a gas tankless and took it out about two weeks later - notable decrease in water pressure which was intolerable to me
 
If you lose water supply in an earthquake, you still have 40 gallons or whatever in a conventional heater. Just make sure it's double-strapped!
 
I have three long haired females in my house, and two want to shower and the third wants to bathe, all in the evening. It works very well for our needs.

Ours is gas, however.
 
I’m all electric
 
frfly172 said:
Think it wastes a good deal of water ,getting to the point of use,and if you turn it off for a few seconds ,you have to wait for it to go through all the pipes to get hot again.
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How is that different from a tank heater?
 
I have one house with on-demand water heaters and one with a high efficiency boiler that provides hot water to the forced air heat system and domestic hot water. The first is in a warm climate and the second in a cold climate. Both provide endless hot water with excellent energy efficiency. I'll never have another tank type hot water heater.
 
If you decide to put a tankless in series reduce the temperature in the tank and use it as a pre-heat for the tankless unit.
 
We’ve got a propane fired tankless at one house. A 100 pound propane bottle will last about 4 months when we are there full time. Wouldn’t go back to a tank type if you paid me.
 
GRG55 said:
If you decide to put a tankless in series reduce the temperature in the tank and use it as a pre-heat for the tankless unit.
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Yeah, was thinking I’d do that as well.
 
there is six of us.....and have never had an issue running out of hot water. The newer versions regulate heat well and are well insulated. Upping the temps can extend the amount of hot water available.
 
Salty said:
I’m all electric
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For comparison to gas the electric specs on the one I looked at:
4.5 gpm
240v
120 amp load

They stated at 1-2 gpm would give a 80-90 rise in water temp; at 4-5 gpm 44 deg increase. Plus they recommended three 50 amp breakers and 8awg wire minimum. The unit was $1000+ and the elec mod would have been $600+ as i had to drop in a sub panel. Instead bought the 40 gal tank heater $300, one cable with double breaker that fit in the existing panel and did the install myself.
 
frfly172 said:
Think it wastes a good deal of water ,getting to the point of use,and if you turn it off for a few seconds ,you have to wait for it to go through all the pipes to get hot again.
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Change out your faucet to one with no flow restriction.:D
 
I installed a tankless propane water heater in our RV after many complaints from my wife about the small tanked water heater. Additional benefit of reduced weight in that setting. It works fabulously well. We can make water too hot for my wife and run it at that temp all day long which coincidentally is just a little longer than her showers. For reference, one 100 pound propane tank typically lasts us 6-8 months when full time in the RV.
As Bell206 indicated above, you will need to consider power supply and temp raise needed per gpm flow rate to size it properly.
 
GRG55 said:
If you decide to put a tankless in series reduce the temperature in the tank and use it as a pre-heat for the tankless unit.
Click to expand...

But you have to have it hot enough to prevent legionnaire disease


Sent from my iPhone using Tapatalk
 
Not sure why anyone installs tanked heaters anymore, unless they are just flipping the house.

Between the extra space you save, efficiency, not running out of hot water when you take a long shower or fire up the hot tub, just doesn’t make sense to me
 
James331 said:
Not sure why anyone installs tanked heaters anymore, unless they are just flipping the house.

Between the extra space you save, efficiency, not running out of hot water when you take a long shower or fire up the hot tub, just doesn’t make sense to me
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No natural gas piped into houses around here. Getting propane deliveries is an extra expense and service, plus you end up with ugly tanks outside the house, especially if you go with a big submarine tank. Preferences, I guess.
 
Checkout_my_Six said:
Easy, Because they’re cheaper....
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And they are more reliable.

Everyone is fascinated with high efficiency furnaces and tankless water heaters, but they have more failure modes than conventional appliances. I keep a spare igniter, spare control board and a spare step down transformer (110 to 24 v) for the high efficiency heating boiler in my house because those are the three things most likely to fail in the middle of a cold winter night.

The old pilot operated gas furnace and water heater tank in my parent's house ran for decades and only needed the burners cleaned periodically. No spare parts whatsoever.
 
Don't know where you're installing this but my only word of caution would be, if you're in an area of hard water, then you might think twice. I installed about 50 electric tankless WH'ers over about 8 years and in almost every case, when the water was hard, the WH lasted less than a year (which, unfortunately, was my warranty period).

Installed four or five different brands, didn't matter which one, none of them liked hard water.
 
timwinters said:
Don't know where you're installing this but my only word of caution would be, if you're in an area of hard water, then you might think twice. I installed about 50 electric tankless WH'ers over about 8 years and in almost every case, when the water was hard, the WH lasted less than a year (which, unfortunately, was my warranty period).

Installed four or five different brands, didn't matter which one, none of them liked hard water.
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The water is coming from a well in limestone, so yeah, it’s a “tiny” bit hard. But, I do have a softener on the front side of the heater, so that should be mostly mitigated.
 
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