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Illinois Licensed Plumber
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Ron,

Don't the tees have to be equally spaced between the WH's to draw equally?
When you do the first in last out method, the tees pretty much automatically space them selves out equally. The idea is the first tee on the cold supply is by the first heater so it gets the cold water first, and the second heater has the other tee on the hot side, the distance between the tee's and the other heater will be the same, and the second heater is the first one out which makes the one getting the water in first to be last out.

Do not ask me the physics behind it, I am not that good at explaining it. All I can tell you is it works.

Here is another diagram from ao smith with three heaters, and you can do this all day with as many as you want.
 

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So what happens when the hot outlet clogs with scale, rust, or some crap? The other heater will then take all the demand and won't be able to keep up. Customer complains of running out of hot water, but the elements and Tstats check out good. This is the reason I do it in series. Parallel seems like there is room for trouble maintaining steady temp.
 

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Professional Bullshioter
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Parallel seems like there is room for trouble maintaining steady temp.
Not really. I use a manufacturer recommended and code required temperature mixing valve on the combined outlet.........

It is the only way multiple tanks get piped from my shop. My way is always the right way. Just ask me..:)
 

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Illinois Licensed Plumber
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If plumbed in series, wouldn't it make sense to set the first heater to 90 degrees, and the second heater to the 120 degrees? This way both heaters will only have to do a 40 degree temp rise each and both get equal use then. Our average inlet water temp here is 50 degrees so my math works for us.

I still agree 100% with ILPlumber first in last out is the best and only way to plumb in more than one water heater.
 

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Watcha Got
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When you do the first in last out method, the tees pretty much automatically space them selves out equally. The idea is the first tee on the cold supply is by the first heater so it gets the cold water first, and the second heater has the other tee on the hot side, the distance between the tee's and the other heater will be the same, and the second heater is the first one out which makes the one getting the water in first to be last out.

Do not ask me the physics behind it, I am not that good at explaining it. All I can tell you is it works.

Here is another diagram from ao smith with three heaters, and you can do this all day with as many as you want.
This his called reverse return.

It is the easiest and fastest way to equalize the piping. If you put it in. Series you will not be utilizing both heaters 100% like RR or the older equalization method.
 

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philosopher and statesmen
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series is the best method

:thumbup:SERIES IS THE BEST :thumbup:

Parallell never draws equally in the first place... most units installed in parallell never draw equally anyway from day one......one heater always does more of the work than the other one...... Unless you install gate valves and flow meters on the units to guage them properly...... which is a joke in the real world...

dont forget that over time those dialectric unions
start to corrode on top of those Parallell heaters and eventually the two units are totally out of sync.....

dont forget that lets say 5 years from now one of those parallell heaters starts to leak,,,
the new unit you install ,, under warranty, probably wont be a perfect exact match, so they wont draw equally once you butcher up the plumbing to get the new unit installed in PARALLELL....

We run into this issue all the time....:blink::blink:


if you install them in SERIES you never have an issue with even or restricted flow....

and you certainly get a full 80 or 100 gallons of hot water versus only maybe 60 gallons off a parallell restricted clogged up unit..



 

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Illinois Licensed Plumber
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:thumbup:SERIES IS THE BEST :thumbup:

Parallell never draws equally in the first place... most units installed in parallell never draw equally anyway from day one.........

....dont forget that over time those dialectric unions
start to corrode on top of those Parallell heaters and eventually the two units are totally out of sync.....

dont forget that lets say 5 years from now one of those parallell heaters starts to leak,,,
the new unit you install ,, under warranty, probably wont be a perfect exact match, so they wont draw equally once you butcher up the plumbing to get the new unit installed in PARALLELL....

We run into this issue all the time....:blink::blink:


~snip~
If you plumb it in first in last out like the pictures I posted, they will always draw equally. As for dielectric unions, I use brass unions which is allowed per our code. Watts also makes a brass dielectric union.
 

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philosopher and statesmen
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If you plumb it in first in last out like the pictures I posted, they will always draw equally. As for dielectric unions, I use brass unions which is allowed per our code. Watts also makes a brass dielectric union.

it appears that your sketches are for more of a commercial application....brass dialectric unions probably cost 5 times more than the average residential parts we deal with every day....

no one ever goes through that kind of trouble and expence here in the boondocks of Indianapolis.....

I am thinking about the common home plumbing systems we run into every day....which are usually not installed with anything but the cheapest stuff you can install....

still like in your skecth,
that when one of those goes bad, and has to be replaced with something not exactly similar....
it pretty much messes up the mojo and flow for all
three of them...


so what have you been up to this year so far??.
 

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Illinois Licensed Plumber
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~~~~~~~~~~~~~~~

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so what have you been up to this year so far??.
Trying to stay alive, health wise and work wise. I am going to start going to commercial places and hotels, and introduce myself and give them some info about our company.
 

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Watcha Got
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it appears that your sketches are for more of a commercial application....brass dialectric unions probably cost 5 times more than the average residential parts we deal with every day....

no one ever goes through that kind of trouble and expence here in the boondocks of Indianapolis.....

I am thinking about the common home plumbing systems we run into every day....which are usually not installed with anything but the cheapest stuff you can install....

still like in your skecth,
that when one of those goes bad, and has to be replaced with something not exactly similar....
it pretty much messes up the mojo and flow for all
three of them...


so what have you been up to this year so far??.
You have to use dielectric unions here for water heater. If you have more than one tank type heater. It really is a piece of cake. If there is room it is more cost effective and better to have two 40's than one 75 gallon electric heater.
 

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Tipsforplumber said:
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