# Dual Water Heaters



## robwilliams (May 6, 2011)

We had a customer call to ask for a price on dual 40 gal water heaters in place of one 75 gallon. Just curious if anyone here has much experience with this. I know, if they are both the same same age and hooked in series, the primary heater will/should fail sooner than the secondary heater since it does most of the work. I have always thought, one heater is better than two. I know this subject has many pro's and con's but what do you all think?


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## Gettinit (May 9, 2012)

Heaters in series is bad, bad and wrong.


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## BigDave (Mar 24, 2012)

robwilliams said:


> We had a customer call to ask for a price on dual 40 gal water heaters in place of one 75 gallon. Just curious if anyone here has much experience with this. I know, if they are both the same same age and hooked in series, the primary heater will/should fail sooner than the secondary heater since it does most of the work. I have always thought, one heater is better than two. I know this subject has many pro's and con's but what do you all think?


After adding up all the expense of the change out, why would anyone go with two heaters to gain 5 gals. of capacity? Plumbed in "series" is just wrong anyway you look at it...


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## rollsdownhill (Jul 17, 2012)

why do they want to do this,, did they say? is it gas or electric, commercial or res.?


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## Gettinit (May 9, 2012)

Install it equalized or reverse return. It makes a great deal of sense for two heaters. One big one is its cheaper. One more big thing is faster ability to replenish hot water.


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## TallCoolOne (Dec 19, 2010)

Gettinit said:


> Heaters in series is bad, bad and wrong.


Why do you say that. In my city most have (2) 50 gallon gas water heaters in the attic

Average house is around 3,800 sq. ft with 4 bathroom groups

Seems to be no issue here as in "bad" or "wrong"


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## GREENPLUM (Jul 27, 2008)

http://www.plumbingzone.com/f7/dual-water-heaters-3110/


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## GREENPLUM (Jul 27, 2008)

go tankless


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## Gettinit (May 9, 2012)

TallCoolOne said:


> Why do you say that. In my city most have (2) 50 gallon gas water heaters in the attic
> 
> Average house is around 3,800 sq. ft with 4 bathroom groups
> 
> Seems to be no issue here as in "bad" or "wrong"


 I am for 2 water heaters in 1 application. Piping water heaters in a series is bad practice and is wrong.


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## rollsdownhill (Jul 17, 2012)

need more info,,, why they want it, what the problem was (if any) in the first place, electric or gas (do they plan to increase the input?), commercial or res, in series or simultaneous operation? there may be a better way,,,


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## BROOKLYN\PLUMB (May 21, 2010)

Sometimes usually due to space I will install 2 40/50 gal. Water heaters twined in, one of the draw back is I'm then required to have an engineer sign off on the chimney the benefit is that with higher recovery rates of a new 50 almost if not beats an old 75 which may be oversized in the first place, so if one goes you can isolate it and not worry about paying $250 violation fee a day for not providing hot water to tennents. I have seen many buildings who simply do it to have backup systems. 

But I agree if it fits and sized right one heater is more cost and energy (cost) efficient especially in a single family residential 

Go tankless


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## High-plumbing (Jan 8, 2012)

Any one have any luck cranking up a water heater and then using a tempering valve to get more hot water out of a smaller unit? Parallel always it's the difference between being a professional and just taking the easy way out.


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## Gettinit (May 9, 2012)

High-plumbing said:


> Any one have any luck cranking up a water heater and then using a tempering valve to get more hot water out of a smaller unit? Parallel always it's the difference between being a professional and just taking the easy way out.


Yes, I have done it (tempering valve). It has to be done with many boilers. Making sure you have the proper valve and flow rate are the important things to consider.


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## Gettinit (May 9, 2012)

BROOKLYN\PLUMB said:


> Sometimes usually due to space I will install 2 40/50 gal. Water heaters twined in, one of the draw back is I'm then required to have an engineer sign off on the chimney the benefit is that with higher recovery rates of a new 50 almost if not beats an old 75 which may be oversized in the first place, so if one goes you can isolate it and not worry about paying $250 violation fee a day for not providing hot water to tennents. I have seen many buildings who simply do it to have backup systems.
> 
> But I agree if it fits and sized right one heater is more cost and energy (cost) efficient especially in a single family residential
> 
> Go tankless


Why in h3ll do you need an engineer? All the info is in the code books.


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## southernplumber (Jul 19, 2012)

There is a proper way to install this "in series " is no good the piping should be a "reverse return" method balancing out the units first unit to get cold is the last to get hot and the first to get hot is the second to get cold this will balance out both units assuring equal work load I think tankless would be a good option although as we all know you size tankless by the bedrooms not the bathroom a large family may need more than one in which case you would even more so need to install two tankless units in reverse return piping as well


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## Gettinit (May 9, 2012)

southernplumber said:


> There is a proper way to install this "in series " is no good the piping should be a "reverse return" method balancing out the units first unit to get cold is the last to get hot and the first to get hot is the second to get cold this will balance out both units assuring equal work load I think tankless would be a good option although as we all know you size tankless by the bedrooms not the bathroom a large family may need more than one in which case you would even more so need to install two tankless units in reverse return piping as well


There is no proper/good way to install tank type heaters in series. Where abouts are you from? Plumber or boiler man/woman?


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## rjbphd (Feb 5, 2010)

Gettinit said:


> There is no proper/good way to install tank type heaters in series. Where abouts are you from? Plumber or boiler man/woman?


 Yea, really... did I miss the intro???


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## southernplumber (Jul 19, 2012)

Mechanical engineering degree master plumber originally southern va since been hired as state hot water heater technical support for the dc area I hope you revise your statement we can go all night long boilers water heaters tankless i don't know it all I'm always up for more insight tell me a better way to install two existing in series units or tankless


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## Tommy plumber (Feb 19, 2010)

southernplumber said:


> Mechanical engineering degree master plumber originally southern va since been hired as state hot water heater technical support for the dc area I hope you revise your statement we can go all night long boilers water heaters tankless i don't know it all I'm always up for more insight tell me a better way to install two existing in series units or tankless


 






http://www.plumbingzone.com/f3/why-post-intro-11368/


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## Gettinit (May 9, 2012)

southernplumber said:


> Mechanical engineering degree master plumber originally southern va since been hired as state hot water heater technical support for the dc area I hope you revise your statement we can go all night long boilers water heaters tankless i don't know it all I'm always up for more insight tell me a better way to install two existing in series units or tankless


Tankless doesn't matter since the units take care of it themselves....that is wrong. There are two proper ways that I know for tanks. One is a reverse return which you should be familiar with. And the old school way of equalized piping is the other. Easiest by far is RR. There is no all night fumbling with this. Maybe you are a little misinformed on what series means. One into the other and then to the faucets. Will they work yes but you will not be giving the same amount of hot water with the same recovery like the other two options thereby making it a crap installation. If it was RR or equalized you draw from both tanks equally and recover equally. There is no comparison for recovery.


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## southernplumber (Jul 19, 2012)

Key word "reverse supply return" I clearly stated in series was not the way to go encourage you to do your research


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## Gettinit (May 9, 2012)

southernplumber said:


> There is a proper way to install this "in series " is no good the piping should be a "reverse return" method balancing out the units first unit to get cold is the last to get hot and the first to get hot is the second to get cold this will balance out both units assuring equal work load I think tankless would be a good option although as we all know you size tankless by the bedrooms not the bathroom a large family may need more than one in which case you would even more so need to install two tankless units in reverse return piping as well


Maybe I was confused by the sentence saying..."there is a proper way to install this in series." 

After rereading it again, I see that you did mean to come across that way and I missed it.


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## Redwood (Sep 8, 2008)

southernplumber said:


> Key word "reverse supply return" I clearly stated in series was not the way to go encourage you to do your research


Here is a keyword for you...

Intro!

Why don't you do one?


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## southernplumber (Jul 19, 2012)

I got this APP on my phone bored one day I guess the only way to create one I've created the profile yesturday I hvnt even seen the option for an intro guys if I can't be taken seriously until I make one lol then I guess I have only one option to fill it out


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## Gettinit (May 9, 2012)

southernplumber said:


> I got this APP on my phone bored one day I guess the only way to create one I've created the profile yesturday I hvnt even seen the option for an intro guys if I can't be taken seriously until I make one lol then I guess I have only one option to fill it out


I already take you serious now that I understand what you wrote. But an intro is required by this forum.


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## Redwood (Sep 8, 2008)

southernplumber said:


> I got this APP on my phone bored one day I guess the only way to create one I've created the profile yesturday I hvnt even seen the option for an intro guys if I can't be taken seriously until I make one lol then I guess I have only one option to fill it out


Try this link...

http://www.plumbingzone.com/newthread.php?do=newthread&f=3

Everybody will say welcome and then we'll all have a real good time... :thumbup:


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## southernplumber (Jul 19, 2012)

Will do gentlemen


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## southernplumber (Jul 19, 2012)

I hate to do this I can't help it I'll update my intro tonight but which tankless are we referring too state rinnai navian ? I challenge you to google cascade multiple unit piping diagram you will see these units need to be rr piped state(tagagi) units will alternate 12hr master slave positions but does not does not regulate flow to one unit... Tankless units do not mechanically try to oppose natural physics ...balance your units other units won't switch master slave positions but indeed need to be piped in rr if not the slave will only fire when master is at 100% btu load rather than a rr system when a slave will ask for help at 75 % btu load or even worse slave short cycles (a tail as old as time a little information can be dangerous) btw if there is a unit other than said products I've listed that modulates flow idk about them bottom line any tankless that uses mechanics over physics will loose my opion


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## Redwood (Sep 8, 2008)

southernplumber said:


> I hate to do this I can't help it I'll update my intro tonight but....


No Buts Aboudit...

Here's where we start being azzoles...


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## Tommy plumber (Feb 19, 2010)

Redwood said:


> No Buts Aboudit...
> 
> He's where we start being azzoles...


 






Speak for yourself Red. I can be a raging a$$ole.......:laughing:


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## pilot light (Apr 21, 2012)

I hate when HWT duel, because Iam forced to choose!


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## PlumberJake (Nov 15, 2010)

What do you guys do when one of the heaters piped in parallel fails after 10 years? More than likely replacing one of the two units will change the pipe lengths because the replacement heater will not be the exact same height as the older unit that is still working. Do you replace both heaters? If so, where is the benefit over installing one large wh? 

I understand piping in series is the least desirable choice, but at least I know that 2 40 gallon heaters will absolutely provide 80 gallons of hot water. And when one of them fails you have a 50/50 shot of still having hot water before replacing/repairing the failed unit.


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## BROOKLYN\PLUMB (May 21, 2010)

Gettinit said:


> Why in h3ll do you need an engineer? All the info is in the code books.


Its required whenever we do an oil to gas conversion and install 2 water heaters. I guess the engineers have a good lobby or the plumbers don't want the liability either way its the customer who pays


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