So I had a Tankless but..

[Brent Dacus]

Ok some simple stuff.
I live in Tennessee so in general it maybe gets to 20 on rare occasion.
I like constant and consistent hot water.
I don't mind the start up phase cold then hot. (dont need Instant heat)
We have 2 people and we shower everyday. 20 plus min per person.

I seems to feel like by reading some post here. Yall think Tankless is not the way to go in general. Can you all educate me on why it not a good idea. Seems like everyone wants it to be the wave of the future..

 

[Terry]

A tankless may need de-liming with vinegar if you hard water on a regular basis if the water is hard.
I have a tankless at the moment. The plus is that I don't worry who is using showers before me. It's not going to run out.
If the power is out, I'm also out of hot water. The gas tank gave me hot water all the time.
I could pick up a battery backup power supply for it though. It did reduce my gas bill.

 

[Sponsor]

 

[Reach4]

I seems to feel like by reading some post here. Yall think Tankless is not the way to go in general. Can you all educate me on why it not a good idea.

Lots of parts. Needs fairly soft water to even be covered by warranty. People say they last longer, but I suspect that is because they are so expensive that they get repaired. A tank water heater is seldom repaired, but is usually considered to be a replaceable unit. There are plumbers who will actually replace parts on a tank WH, but I think they are in the minority. I am not a plumber. I also expect 20 years or more out of a tank type natural gas WH, but others have much lower expectations.

Is there a problem with your current WH? Or are you motivated by some other factors?

Tankless is a good idea in some cases. They are much more popular in Europe where power costs maybe 3x what it does in TN.

 

[Brent Dacus]

Reach No problems just research
I am building a home soon.. So in my last house I had a tankless on Natural Gas. I loved it. Mostly for the continuous hot water. I also heard they were more efficient. We also had 50 gallons of water over our heads in the attic. Which we didn't like..

Any respected brands yall do like? I had a Rinnai it was fine. I am open to suggestions. No hard water problem and will be on Natural Gas.

 

[Brent Dacus]

The plus is that I don't worry who is using showers before me. It's not going to run out.

Yep..

No hard water here all softened. Is the battery backup for the igniter?

 

[Terry]

Navien makes a model with built-in recirc. That helps with the hot water delay.

http://us.navien.com/Product/Category-NPE-A series/

 

[Brent Dacus]

Navien makes a model with built-in recirc.

Thanks

 

[Dana]

Rinnai is the world's largest manufacturer of gas-fired appliances. If you were happy with your other Rinnai, you'd be happy with another one. You'd probably be more than happy with a Noritz too. Whatever the brand, local support (particularly installer training) is an important factor. The most common problems with them is usually due to installer error.

In Europe & Asia tankless solutions are popular primarily for the space savings due to smaller home sizes, not higher efficiency.

If you're interested in showering-efficiency a drainwater heat exchanger and a standard 40-50 gallon gas burner would give you pretty the same "endless shower" experience with less maintenance, provided you have at least 5' of vertical drain downstream of the shower. This is not a solution for one story slab on grade houses. With a 2 story house with the shower upstairs, or a one story with a sufficiently deep crawlspace or basement foundation it works great.

For the average home in TN it's probably not cost effective, but if you're really running the shower 40 minutes + per day it will have a pretty decent return on investment- much better than the difference between a tank and a tankless. They're effectively zero maintenance, and have a 35-40 year + lifecycle before performance drops to 75% of the day-1 return efficiency. The biggest and fattest one that fits is the "right" one, since the additional cost of goods is outweighed by the higher return efficiency.

It takes a 3" x 60" or longer, or a 4" x 48" or longer to reach a 50%+ energy return efficiency required to make a standard tank into an endless-shower experience. Don't expect to find them on the shelf at the local plumbing supply or box store, but they can be ordered direct from the manufacturers (most of which are Canadian, with at least one exception) , or through Home Depot.

A basic gas-fired hot water tank runs at about 80% thermal efficiency, but if you're recovering 50%+ of the heat that would otherwise be going down the drain in 20 minute showers it's better than 120% as-used net efficiency, something a tankless on it's own would not be able to achieve. Of course, you could install one of those with a condensing tankless too, where you'd be pushing 150% net efficiency.

 

[Brent Dacus]

Dana. Thanks your detailed replies are wonderful. Looked at Noritz. Seems good. What make you say I would like them better. I have a local install / service company. I wont have a basement so the hot recovery thing I suppose is a no go.

 

[Dana]

"...more than happy with..." isn't to be construed as "will like it better". "Will like it as much as..." would be closer to my intent. Noritz is a high quality high reliability manufacturer. I haven't compared recent models apples-to-apples on specs, but traditionally Noritz models often had better temperature control at low/very-low flow.

A 2-story slab on grade with the shower upstairs can be a good candidate for drainwater heat recovery, but never a 1-story ranch with slab-on-grade foundations. I threw the concept out there based on your reported high daily shower times, figuring that in new construction there is some flexibility and it make a difference in where you put the main shower. You don't need a basement, only a reasonably tall vertical section of drain, which is usually available in most 2-story houses with an upstairs bathroom/master-bath.

 

[Brent Dacus]

"...more than happy with..." isn't to be construed as "will like it better". "Will like it as much as..." would be closer to my intent. Noritz is a high quality high reliability manufacturer. I haven't compared recent models apples-to-apples on specs, but traditionally Noritz models often had better temperature control at low/very-low flow.

A 2-story slab on grade with the shower upstairs can be a good candidate for drainwater heat recovery, but never a 1-story ranch with slab-on-grade foundations. I threw the concept out there based on your reported high daily shower times, figuring that in new construction there is some flexibility and it make a difference in where you put the main shower. You don't need a basement, only a reasonably tall vertical section of drain, which is usually available in most 2-story houses with an upstairs bathroom/master-bath.

Dana thanks. I will check noritz out. So the recover thing will that work with a tankless I think you said yes? The main shower will be on the 1st floor with a 2' crawl space. Has to be vertical right? Works with pvc dwv and pex or copper?

 

[Dana]

It has to be vertical, and can work with any type drain. It basically replaces a section of drain pipe with a section of copper drain that has been pre-fabricated with a potable water pipe slinky tightly wrapped around it. If you have only 2' of clear vertical run to work with the return efficiency isn't going to be more than about 30% even with a 4 incher. Most manufacturers don't build them shorter than 2.5' (30"). A 4" x 30" delivers about 35% return efficiency at 2.5 gpm, but almost anybody's 4" x 48" delivers about 50%, give or take. Whether it's worth digging a sump pit in the crawlspace deep enough to accommodate a 4-footer, and burying the main drain to the house that deep isn't something that I can tell you.

Retherm claims 48% efficiency for their 4" x 30", but I'm skeptical of that claim, since it is not independently tested and listed with Natural Resources Canada, as most other manufacturers' models are. The NRCan-maintained apples-to-apples list of third party tested models in spreadsheet format lives here.

The potable connections are all sweat-copper, but any plumbing supply would have adaptors to PEX or PVC. A Fernco type drain coupling works for mating them to other types of drain pipe. Add at least 8" to the vertical height requirement to accommodate the couplings.

There is one model out there that can operate horizontally, but it's not an NRCan tested product, so the apples-to-apples efficiency is unknown. It should deliver return efficiencies in the mid-to-high 30s if mounted at a 30 degree angle, if their marketing isn't complete BS. It was reviewed in this bit o' bloggery back in December 2014. The EcoDrain A1000 is their third or fourth generation model. The current one is 56" long and designed to hook up with 2" drains. It's efficiency increases with the steepness of the installed angle (up to a max of 75 degrees). With 24" of headroom you'd be able to install it at something like 30 degrees, so you'd be in the mid-range of their 30-45% return efficiency estimates.