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Experiences With A Tankless Hot Water Heater

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Another Takagi onwer on December 19, 2005:

for most norht american plumbing pipe size is by i.d. (inside diameter ) not o.d. (outside diameter).This is the case for black iron pipe such as you mention for the gas supply. So the correct size reference would be 3/4". Side wall thickness changes with application so the o.d. will change for the same nominative pipe size.Typically iron pipe in gas is spec'ed as schedule 40.High pressure apps would use sced 80 , and 160 . Tubing however is specified by o.d. , so to know the equivalent capacity to pipe you have to know the wall thickness. Rigid copper pipe is i.d. copper tubing is o.d. It would help people if you correctly refered to the iron pipe in your article as 3/4" ( which I believe you will find on the table Takagi includes , and they refer to 3/4 pipe as the connection size ( i.d. implied ).3/4" o.d. would be inadequate to supply the maximum output.

Anonymous on January  6, 2006:

Thank you for your information on this. It was very helpful.

Anonymous on April 17, 2006:

thanl you for your info--godd to hear from someone not trying to sell me!!

Anonymous on June  7, 2006:

The info on low flow rate shut off is great!

I have read a lot on tankless heaters and not come across that fact.

Thanks


Collecting Information on July 29, 2006:

I've been replacing older appliances with more energy efficent ones over time. Heat/AC, Washer/Dryer, Dishwasher, Refrigerator, ect. I've been hearing a lot about Tankless Water heaters and I was curious about ones experiance on such device. I have an older home that isn't all that efficent and I've been doing what I can to help keep cost down. Adding Insulation to the attic made a huge differance in comfort and cost. Especially here in Texas. Thanks for sharing your experience on this and look forword to seeing updates in the future.

Anonymous on January 24, 2007:

Wouldn't it work better if you had a tankless cold water heater? It don't make a lot of sense to heat water that's already hot.

jep on January 31, 2007:

Jan, I have a general question.

I am researching water heaters with the idea that my elderly house has an elderly water heater which will need replacement.

I've heard tankless water heaters can deliver unevenly heated water; that is, if you are taking a shower and the washing machine (for example) starts using water, your shower temperature can drop. Then when the washing machine stops using water, your shower temperature can rise sharply. Have you had any problems with that?

Also, Lowe's currently advertises on certain models, "This product may qualify for a $300 tax credit". I don't know the details of that tax credit but it may reduce the cost of a $1000 tankless water heater to $700, which would be comparable to a standard water heater.


Jan Wolter on April 25, 2007:

All tankless hot water heaters have a limit on how much water they can heat per minute. As long as you don't exceed that limit, I think the water will be delivered at a consistent temperature. If you do exceed that limit, then something is clearly going to happen.

What happens depends on the heater. Some will simply deliver water that isn't entirely heated up to the desired temperature. Mine is a little fancier. If it hits the limit, it will continue to deliver water at 120 degrees, but it just won't allow more to flow through the meter.

Not that that'll prevent temperature changes in your shower. Since you control your shower temperature by mixing hot and cold, changes in the flow rate of the hot water are going to feel like temperature changes.

I've never had this problem though. Basically, you need to get a big enough heater for your needs.


Steinebach in Portland, OR on July 22, 2007:

Thanks for the informative article. Your comprehensive article answered
a question that I had on the low volume shut off. I use minimum flow
when I shower and was worried that the system might shut down at some
minimum flow level. You answered that question - it does. Now I need to
know if a smaller system might work better. My plumbing contractor is
trying to sell me what I think is a whole house tankless water heater
and I only need it for one bathroom. Nothing else will be drawing hot
water from it. Time for more research.


Jan Wolter on August 11, 2007:

If you're worried about this, I'd do some experimenting and try to come up with an estimate of how many gallons per minute of hot water you are actually using when you shower. Maybe you could set the shower how you like it, then measure the total water flow. (I used a gallon milk jug and a stop watch to do this.) Figuring out what percentage of that water is hot is probably trickier. Probably the best way would be measure the water temperature you shower at, the hot water temperature and the cold water temperature. This should give you a decent guess at what percentage hot water you are using.

If the total hot water usage is in the neighborhood of the hot water heater's shut off, then you may have a problem. I expect, however, that most people won't have one. The shower I had a problem with was set to use much less water than a normal low-flow shower head, and even then we only occasionally had problems.


meredith gossland on April 20, 2008:

Thanks for a great article, clearly written. I learned a lot! Just one 
thing about the electric heaters. If you have solar energy as little as 
50 watt panels you might be able to power your heater in the event of 
power failure. Even when it is extreamly cold, if you have a battery 
backup powered by solar you be ok.

Once again thanks so much for the info! 

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