# Recirc with tankless is like paying taxes . . .



## klempner (Mar 4, 2011)

The conventional wisdom of course is that recirc with tankless is bad because tankless will run continually, which defeats the purpose, and will increase gas usage, not decrease it. And the corollary, therefore, is that you need tank if going to recirc. But I got to thinking, the loop will be the same heat sink either way, which means it should require the exact same BTUs (amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit) to recirc whether it’s tank or tankless. The exact same. Which is to say, even though the burner would on the tankless might be on continuously, and even though the burner on the tank would cycle on and off, wouldn’t it still be the exact same BTUs? And wouldn’t it actually be less BTUs on the tankless because we would be going from .68 to .82 efficiency, or better? Which is to say, is the moral of the story—and perhaps I’m totally wrong and missing something obvious—but isn’t the moral of the story that recirc with tankless just shows much more dramatically how much energy recirculation uses? Same “taxes”; it’s just that the tankless makes you pay with cash, and so the tank makes it a lot more palatable.

Heck, maybe I’m totally wrong. I'll keep thinking.


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## rjbphd (Feb 5, 2010)

Thought you claimed to be a master plumber

Sent from my SM-G386T using Tapatalk


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## hanzkunzel (Feb 24, 2017)

You should look into Circ Logic with Rinnai. It's built in to the unit and you wire the pump to the unit.

https://www.rinnai.us/documentation/downloads/Rinnai_Circ-Logic.pdf

The bills on the circ is all about the timing on the pump, the insulation on the whole piping system, and Temp setting on the unit.

If you have a house with no insulation on the pipes and a pump running 24/7 you might as well unplug that pump and go to a strip club. You'll get more fun for the money.


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## dhal22 (Jul 30, 2010)

Put a motion sensored high speed pump in your master bath area and just draw the hot water when you need it. No need to worry about your tankless running all the time.


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## panther (Oct 27, 2010)

I use the Naviens with circ pumps in them. They seem to work very well. Slight difference in gas usage. I did use a small 2 gallon electric water heater and a Grundfos on a dedicated return line for a tankless once and that also worked very well.


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## wyrickmech (Mar 16, 2013)

Intellahot has a build in circulator that learns flow rates over a 7 day period then turns on and off as the need has been recorded. As it changes so does the on and off times. Some Majorly cool stuff coming out on the markets.


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## chonkie (Jul 31, 2014)

klempner said:


> The conventional wisdom of course is that recirc with tankless is bad because tankless will run continually, which defeats the purpose, and will increase gas usage, not decrease it.



Tankless was not designed to save gas, it was designed to provide endless hot water.


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## sparky (Jan 8, 2014)

Tankless is nothing but pure junk,if not maintained on regular basis warranty no good,to much maintence and cost,heck you can buy 3-4 tank units,put a pump on them,add a aquastat and you are good to go


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## hanzkunzel (Feb 24, 2017)

sparky said:


> Tankless is nothing but pure junk,if not maintained on regular basis warranty no good,to much maintence and cost,heck you can buy 3-4 tank units,put a pump on them,add a aquastat and you are good to go


I will have to disagree with this. The initial tankless install is indeed triple the price, but it does pay for the difference in the lifetime of the unit with energy savings which is nearly double that of a tank. Plus, if installed correctly with a flush kit the homeowner can flush the unit themselves for the initial cost of the kit and cost of one quart of cleaner every flush after that. Also you can get away flushing the unit every two years and be alright when not being used in a commercial setting or very large family. I will also put that tanks tend to fail by leaking and on occasion can cause a tremendous amount of damage when they do. Tankless units are all copper, brass, and o rings with no tank to go bad. The chance is still there for a flood, but the chance goes down significantly which to me is worth the cost.

EDIT - I'm referring primarily to Rinnai which I believe is the best on the market. There are many other brands now that have them and in my opinion if you have an Eternal or a Bosch you are dealing with a fairly trash unit and you shouldn't judge the "tankless group" with one of those.


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## Debo22 (Feb 15, 2015)

Just changed a Rinnai heat exchanger that was leaking. It was three years old and under warranty. Tedious work, about 500 screws. Good thing is they have a sensor in the bottom that shuts off water if it senses a leak.


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## sparky (Jan 8, 2014)

Debo22 said:


> Just changed a Rinnai heat exchanger that was leaking. It was three years old and under warranty. Tedious work, about 500 screws. Good thing is they have a sensor in the bottom that shuts off water if it senses a leak.


Thank you for making my point,I stand by my previous statement,tankless heaters are nothin but pure junk:yes:and the ones I have worked on all call for monthly maintence,which is a true pain in the ass and we all know a homeowner is not gonna do


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## Toli (Nov 7, 2015)

hanzkunzel said:


> .....but it does pay for the difference in the lifetime of the unit with energy savings which is nearly double that of a tank.




Show me your math, please


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## sparky (Jan 8, 2014)

Toli said:


> Show me your math, please


AGREE,I also would like to see this "fuzzy math" as George w bush called it :laughing::laughing::laughing::laughing::laughing:


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## dhal22 (Jul 30, 2010)

sparky said:


> Tankless is nothing but pure junk,if not maintained on regular basis warranty no good,to much maintence and cost,heck you can buy 3-4 tank units,put a pump on them,add a aquastat and you are good to go


Good god, we install 4 -5 tankless heaters a month, what maintenance? We charge a premium to install them and the customers are ecstatic with their purchase. So you have endless hot water, good money in your bank account and customers calling and emailing to voice their happiness.

You could, i suppose, descale the heater every year or 2 if you installed a brand that uses copper heat exchangers but roll that into a maintenance program and seriously start providing good service to your customer.

What maintenance may I ask? Dozens and dozens of my long time customers still have the tankless I installed years ago. Some opt for descaling, some don't but the units are still there doing their job.


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## hanzkunzel (Feb 24, 2017)

Debo22 said:


> Just changed a Rinnai heat exchanger that was leaking. It was three years old and under warranty. Tedious work, about 500 screws. Good thing is they have a sensor in the bottom that shuts off water if it senses a leak.


That to me looks like an incorrect install venting wise. Did it have a condensate drain? Was the vent angled correctly? I've seen that look inside heat exchangers of Rinnai all the time with incorrect installs. After a number of years it'll look just like that and potentially leak as it did with your unit you worked on.


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## hanzkunzel (Feb 24, 2017)

And as for math here we go

Cost of Tankless Install 3000 (Good simple average)
Cost of Tank Install 1000 (Also Good Simple Average)

Difference is 2000 bucks.

Tank will last on average 12 years

A tankless if maintained will last on average 20 years

I know by fact and having a rinnai tankless in all 4 houses in my family the gas bill was nearly half that of regular tank. (1200-1400 square foot houses with 2 full bath and circ'd)

Average gas bill since change out has been the bare minimum of 20 dollars a month. Average gas bill before the change was 35 dollars.

So, in the lifetime of a tankless you have 3,600 bucks in savings on gas alone PLUS another 1000 if you choose to add in that you didn't change the tank again in that 20 year span. 

But let's wait here. It's not over. We got to add this maintenance that is so expensive. Let's say you charge a plumber to come out and do it every 2 years. That service call will on average be 145 bucks for a flush and cleaning/inspection. That's a total of 1,450 bucks in the lifetime. So where does that leave us now?

Total cost of savings on tankless with 2 year maintenance in 20 years - $2,150 in gas and if you include the possibility of another tank install after 12 years $3,150. 

Difference is paid.....done

And to note, on tankless there is no T&P, it's just a P. So a lot less chance of changing out T&P's in the lifetime as well. All other maintenance on the water system is the same.


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## Debo22 (Feb 15, 2015)

hanzkunzel said:


> That to me looks like an incorrect install venting wise. Did it have a condensate drain? Was the vent angled correctly? I've seen that look inside heat exchangers of Rinnai all the time with incorrect installs. After a number of years it'll look just like that and potentially leak as it did with your unit you worked on.


Vent was straight up through garage roof and had a condensate drain. I didn't install the unit originally and the homeowner said it has been serviced every year. Most likely was never serviced but they probably heard that the manufacturer can void warranties if it's not. The part was free for him but not the labor.


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## hanzkunzel (Feb 24, 2017)

Debo22 said:


> Vent was straight up through garage roof and had a condensate drain. I didn't install the unit originally and the homeowner said it has been serviced every year. Most likely was never serviced but they probably heard that the manufacturer can void warranties if it's not. The part was free for him but not the labor.


Well then. Bad eggs do happen. I do agree with you though, a **** ton of screws. Haha. But one good thing to put out there though, the unit does indeed shut the water off to itself in that instance and so saved a potential flood that could've happened with a tank if it failed in same situation.


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## sparky (Jan 8, 2014)

dhal22 said:


> Good god, we install 4 -5 tankless heaters a month, what maintenance? We charge a premium to install them and the customers are ecstatic with their purchase. So you have endless hot water, good money in your bank account and customers calling and emailing to voice their happiness.
> 
> You could, i suppose, descale the heater every year or 2 if you installed a brand that uses copper heat exchangers but roll that into a maintenance program and seriously start providing good service to your customer.
> 
> What maintenance may I ask? Dozens and dozens of my long time customers still have the tankless I installed years ago. Some opt for descaling, some don't but the units are still there doing their job.


In my area we have limestone in the ground which makes the water hard,if you don't run a solution through these tankless water heaters once a month they last about three yrs,you can buy 3-4 tank type heaters vs one tankless,what's that about 25 yrs worth of hot water???the ones I have installed called for a solution to be ran through them on a monthly basis,it also said if certain maintence procedures are not done then it would void the warranty.


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## sparky (Jan 8, 2014)

hanzkunzel said:


> And as for math here we go
> 
> Cost of Tankless Install 3000 (Good simple average)
> Cost of Tank Install 1000 (Also Good Simple Average)
> ...


We have limestone in the ground here in ky,these heaters will not last 20yrs here,water is just to hard for them,clogs everything up after just a few yrs


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## sparky (Jan 8, 2014)

hanzkunzel said:


> And as for math here we go
> 
> Cost of Tankless Install 3000 (Good simple average)
> Cost of Tank Install 1000 (Also Good Simple Average)
> ...


Also in my area if you tell someone it's gonna cost them 4000.00 for a water heater they will run you off the property,no one is gonna pay that kind of money to save 15 bucks on a gas bill that the government is already helping them pay,people just will not cough up that kind of money for a water heater


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## HowlingMad (Jun 14, 2011)

sparky said:


> Also in my area if you tell someone it's gonna cost them 4000.00 for a water heater they will run you off the property,no one is gonna pay that kind of money to save 15 bucks on a gas bill that the government is already helping them pay,people just will not cough up that kind of money for a water heater



You're right, my heating and warm water stuff is now exactly working sine 1982, Wood fired heating with Warmwater tank and buffer, it costs abaut 150 € of petrol for the chainsaw every year, about 100 € diesel (gasoline), and 1 week of manned labour by my self, it works, it is a cheap solution and a not so good one ( work everyday) and for 140 squaremeters of home, not insulated, with winters on the edge of -25 degrees celsius it is affordable and efficiant for me and many other ( we need warm water for 4 kids and us 2  ) we need about 30 kubic metres of wood every year. (of couse i am a plumber, but we help together neighbours and stuff) domestic gasses or other minerl stuff ( excebt for my nissan Terrano) is not going to enter my house (and no, I am no hillbilly).


sry for bad spelling, i am not a native english speaker.


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## sparky (Jan 8, 2014)

HowlingMad said:


> You're right, my heating and warm water stuff is now exactly working sine 1982, Wood fired heating with Warmwater tank and buffer, it costs abaut 150 € of petrol for the chainsaw every year, about 100 € diesel (gasoline), and 1 week of manned labour by my self, it works, it is a cheap solution and a not so good one ( work everyday) and for 140 squaremeters of home, not insulated, with winters on the edge of -25 degrees celsius it is affordable and efficiant for me and many other ( we need warm water for 4 kids and us 2  ) we need about 30 kubic metres of wood every year. (of couse i am a plumber, but we help together neighbours and stuff) domestic gasses or other minerl stuff ( excebt for my nissan Terrano) is not going to enter my house (and no, I am no hillbilly).
> 
> 
> sry for bad spelling, i am not a native english speaker.


Man,I have not a clue as to what you just wrote,not a clue.but I think you have an outdoor furnace that heats the water,but I'm not betting on it lolololo


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## klempner (Mar 4, 2011)

thanks for the replies.

“If you have a house with no insulation on the pipes and a pump running 24/7 you might as well unplug that pump and go to a strip club. You'll get more fun for the money.”

I agree that 24/7 recirc with no insulation is a very bad idea. Even with insulation, a very bad idea. But I believe the cost of doing so would be cheaper with a tankless, not more. It’s the same amount of water. Therefore, it’s the same amount of BTUs. Except that it’s less BTUs because tankless more efficient. All of which is to say, I’m assuming my customers with 24/7 recirc on their tanks are paying a small fortune. However bad it is on a tankless, it seems like it would be worse on a tank.

My philosophy would be live in a smaller house, with a centrally located water heater with parallel hot water distribution, above ground, with very good insulation, no recirc other than on demand (or a really smart timer), and perhaps a code change to go along with it all to allow slightly undersized hot water lines (undersized: not have to allow for everything going at once.)

“I use the Naviens with circ pumps in them. They seem to work very well. Slight difference in gas usage. I did use a small 2 gallon electric water heater and a Grundfos on a dedicated return line for a tankless once and that also worked very well.”

I’ve thought about the 2 gallon tank idea. But would have to keep tank at 125 or so (legionella), so might end up with variable temp, since 125 is often way too high for a tankless to meet minimum flow rate to activate. No anode rod, either, in 2 gallon tank, which is probably not a huge problem. But there’s maybe another $50 or $100 a year in electricity. Plus having to factor in a tank probably limits where the tankless would go.

There was a govt study (Minnesota, 2010, “Actual Savings and Performance of Natural Gas Tankless Water Heaters”; pdf on line) that had a very bad verdict on the Navian with buffer tank. Much less efficient than units without buffer. Mentions that the Navian with buffer tank standby losses are 20x higher than without.

“Just changed a Rinnai heat exchanger that was leaking. It was three years old and under warranty. Tedious work, about 500 screws. Good thing is they have a sensor in the bottom that shuts off water if it senses a leak.”

Wow. Is that true? I would think it would take 4 or 5 hours to remove and reinstall 500 screws. My customers would be very upset. Hopefully, it was really only 60 or 70 screws??? How long did it take?

I’ve picked up from this forum that a number of Rinnai heat exchangers have leaked. So I called Rinnai and asked why they still use copper instead of stainless steel. Noritz and Navian, if I’m not mistaken, now use stainless for the primary and secondary. Rinnai only for the secondary. Rinnai person, who was very pleasant to talk to by the way, said the copper is MUCH better at exchanging heat. The Rinnai person did not say this is the reason Rinnai has a lower minimum flow rate than everybody else (.4 gpm to activate, .26 gpm to keep activated), but I am wondering if that’s related. Have no idea. The minimum flow rate problem is my primary hesitation with tankless. Which makes Rinnai, for me, far and away the most tempting brand to use.

I did not know they had an automatic shutoff device. If reliable, that might steer me toward placing the unit more in the middle of things.


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## hanzkunzel (Feb 24, 2017)

klempner said:


> “Just changed a Rinnai heat exchanger that was leaking. It was three years old and under warranty. Tedious work, about 500 screws. Good thing is they have a sensor in the bottom that shuts off water if it senses a leak.”
> 
> Wow. Is that true? I would think it would take 4 or 5 hours to remove and reinstall 500 screws. My customers would be very upset. Hopefully, it was really only 60 or 70 screws??? How long did it take?


You are indeed right, the screw count is between 30 and 40. Takes me on average 3 hours to replace a heat exchanger and all gaskets and orings.


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## Debo22 (Feb 15, 2015)

hanzkunzel said:


> You are indeed right, the screw count is between 30 and 40. Takes me on average 3 hours to replace a heat exchanger and all gaskets and orings.


Seemed like more than 30-40, but at least they each come sealed in their own individual plastic bag for your convenience. :whistling2:


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