# Multiple Water Heaters



## Plumbworker (Oct 23, 2008)

I'm curious what piping methods others perfer on this site for connecting multiple water heaters... parallel or reverse return? I prefer reverse return i think its simpler than stacking several tee manifolds and looks cleaner etc..


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## Plumbworker (Oct 23, 2008)

well alrighty then..


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## SlickRick (Sep 3, 2009)

If reverse return is series, I prefer a balanced parallel.


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## Plumbworker (Oct 23, 2008)

reverse return is not series.. Reverse Return is last heater in first heater out..

Heres a good article on the subject.. In my opinion this is the way to go.. The reason i'm asking is i run into alot of guys piping in parallel with stacking all these manifold tees in a pyramid and i just cant see any benefits from this arrangement vs reverse return 
http://www.plumbingengineer.com/may_12/designers.php


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## CaberTosser (Mar 7, 2013)

I like reverse return, and for Pete's sake keep the headers, valves, unions and gas lines above the tanks to allow for their eventual replacement. When I run across heaters where the piping requires me to isolate the buildings main water to remove the valves & headers I don't have kind thoughts for the original installer.


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## BC73RS (Jan 25, 2014)

CaberTosser said:


> I like reverse return, and for Pete's sake keep the headers, valves, unions and gas lines above the tanks to allow for their eventual replacement. When I run across heaters where the piping requires me to isolate the buildings main water to remove the valves & headers I don't have kind thoughts for the original installer.


You won't have to worry about my installations, this is how I fly...


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## Zionone (Jul 3, 2013)

How well does reverse return work for heaters that are not the same size or different makes or models. I have always piped them with parallel manifolds that were balanced lineally or as close too it as possible.


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## Plumbworker (Oct 23, 2008)

with different sized tanks reverse return would not work that well.. Youre on the right track with doing parallel manifold.. Doing reverse return with different sized tanks would have resistance issues for shure..


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## huskyevert (Mar 9, 2012)

That's a good article. I like Tim. I always read his article first when the magazine comes in the mail.


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## wyrickmech (Mar 16, 2013)

Reverse return should work fine on different sized tanks. You are balancing the flow resistance on the piping system the storage size will not matter. A Parnell is fine too as long as the inlets and outlets are the same size.


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## Plumbworker (Oct 23, 2008)

wyrickmech said:


> Reverse return should work fine on different sized tanks. You are balancing the flow resistance on the piping system the storage size will not matter. A Parnell is fine too as long as the inlets and outlets are the same size.


Reverse return just doesnt seem practical with different sized tanks and or tapping sizes.. in my opinion the tank will have resistance differences it may be very slight and not much of an issue but reverse return is ideal when using identical sized tanks.. Parallel manifold would be much better option for different tanks as it doesn't work on resistance..


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## plumber tim (Jul 4, 2013)

BC73RS said:


> You won't have to worry about my installations, this is how I fly...


Did that get inspected and pass ? It looks like you have a 3/4" vacuum relief on an 1 1/2" feed line. Mass code requires vacuum relief to be not less than one pipe size smaller than the drain valve or supply whichever is larger.


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## Plumbworker (Oct 23, 2008)

plumber tim said:


> Did that get inspected and pass ? It looks like you have a 3/4" vacuum relief on an 1 1/2" feed line. Mass code requires vacuum relief to be not less than one pipe size smaller than the drain valve or supply whichever is larger.


 I've never seen a vacuum relief valve for domestic water over 3/4" before..? who makes em?


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## rjbphd (Feb 5, 2010)

Plumbworker said:


> I've never seen a vacuum relief valve for domestic water over 3/4" before..? who makes em?


Never seen vb on any heaters here..


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## Plumbworker (Oct 23, 2008)

rjbphd said:


> Never seen vb on any heaters here..


I thinks it's mainly a Ma. thing. I do believe upc says somthing about bottom feed tanks needing a vacuum relief valve 6" above the top of tank. Top inlet tanks generally have dip tubes with small vacuum relief holes..


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## plumber tim (Jul 4, 2013)

Plumbworker said:


> I've never seen a vacuum relief valve for domestic water over 3/4" before..? who makes em?


You can use multiple vacuum reliefs to make the equivalent size. I think watts does make larger than 3/4" but no supply houses I know of stock them.


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## Archie (Mar 5, 2014)

BC73RS said:


> You won't have to worry about my installations, this is how I fly...


Nice work. Are the threaded rod and channel for earthquake protection. I hope that's not a stupid question but we don't have to fasten heaters down around here, gravity does the job.


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## rjbphd (Feb 5, 2010)

Archie said:


> Nice work. Are the threaded rod and channel for earthquake protection. I hope that's not a stupid question but we don't have to fasten heaters down around here, gravity does the job.


Its the gravity does the most damage!


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## 422 plumber (Jul 31, 2008)

BC73RS said:


> You won't have to worry about my installations, this is how I fly...


Can I have the contractor rewards points?


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## A Fast Plumbing (Nov 6, 2012)

*Interesting idea but may not be true.*



wyrickmech said:


> Reverse return should work fine on different sized tanks. You are balancing the flow resistance on the piping system the storage size will not matter. A Parnell is fine too as long as the inlets and outlets are the same size.


You can see the reason for and benefit of "Reverse Return" systems. 

I believe that different size tanks would make a difference however. Even with the inlets and outlets being the same size, you must consider the internal component lengths of dip tubes and other such items,


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