# Series or parallel



## plummer98 (Feb 5, 2010)

I have a customer who has 1 -40 gallon electric in their house they want to add a 60 gallon gas moved from another house keeping the first one. I was always taught to pipe in parallel but seeing the I have 2 different ones and will end up being about 15' apart I wanted to see what the consensus opinion is....... Later TY


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## Miguel (Aug 10, 2009)

Depends on a lot of things whether it should be piped in series or balanced manifold.

I'm wondering why you've "always been taught" that they should be piped one way only. :huh:


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## 3KP (Jun 19, 2008)

*Introduction*

Hello young poster. you need to go to section indtroduction and tell us about your self and plumbing skills you have.

then you will get more response


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## Redwood (Sep 8, 2008)

yep make that intro then we'll talk...:whistling2:


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## Leakinator (Dec 2, 2008)

5 valves and you can have both with isolation on either WH


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## Redwood (Sep 8, 2008)

Thanks for making the intro and welcome to the zone...:thumbup:

Proper operation of a parallel installation depends on all components of the system being equal and in complete balance. The size and age of the water heaters included, along with the friction losses in the piping..

In a parallel installation you want a set up where both water heaters will draw equally until depletion. If the water heaters are not matched in size or, age where on outlet may be partially occluded the system will not work.

In your situation if the customer is not willing to pony up for 2 matching water heaters I would go with a series installation.


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## SewerRatz (Apr 25, 2009)

I always learned its best to pipe them in series if they vary in size and or btu rating.

As for piping them in parallel, I always like the first in last out method myself.


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## futz (Sep 17, 2009)

Yes, almost always series. 

So many things have to be exactly right to make parallel work properly. In the real world one tank is going to end up getting more than the other and doing more work. 

In series, one tank does most of the work, so it probably wears out first. The other is mostly a storage tank.

I once piped a pair of tanks in a new house so they could be valved to work either parallel *or* series. Left a neat computer printed set of notes and diagrams on the wall so the owner could try it both ways for a few months each. He was supposed to get back to me and tell me which he liked better, and which was better for the gas bills. Never heard from him. They probably just left it on series.



SewerRatz said:


> As for piping them in parallel, I always like the first in last out method myself.


I like that! I've never done parallel that way. Should work well.

I always did it the center-feed way, with equal length feeds/supplies.


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## TheMaster (Jun 12, 2009)

Couldn't you use a pressure balancing valve and pipe each one of the heaters into it? Wouldn't that make the draw equal from both tanks?


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## Redwood (Sep 8, 2008)

TheMaster said:


> Couldn't you use a pressure balancing valve and pipe each one of the heaters into it? Wouldn't that make the draw equal from both tanks?


I suppose that would probably work...
With some added cost...
Prolly make bypassing one tank a nightmare...

But, the OP is still faced with the unequal tank size...

With the balanced system in parallel you do gain a substantial increase in delivery and recovery rates...


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## TheMaster (Jun 12, 2009)

Redwood said:


> I suppose that would probably work...
> With some added cost...
> Prolly make bypassing one tank a nightmare...
> 
> ...


Yeah the unequal tank size is an issue,the smaller will work harder for sure. To correct that install a throttling valve on the smaller tank and limit its flow but not pressure and then regulate the throttling valve until both tanks empty at the same time.:laughing: before we are through we are going to have a room full of valves :laughing: if that doesn't work then install pressure regulators so you can tweak the pressure on each inlet.:laughing: Watts would love me wouldn't they.....maybe they will hire me to draw their pipe diagrams:jester:


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## Redwood (Sep 8, 2008)

TheMaster said:


> Yeah the unequal tank size is an issue,the smaller will work harder for sure. To correct that install a throttling valve on the smaller tank and limit its flow but not pressure and then regulate the throttling valve until both tanks empty at the same time.:laughing: before we are through we are going to have a room full of valves :laughing: if that doesn't work then install pressure regulators so you can tweak the pressure on each inlet.:laughing: Watts would love me wouldn't they.....maybe they will hire me to draw their pipe diagrams:jester:


Hey us plumbers can make almost anything happen...
It's often just a question of the cubic dollars...:laughing:


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## TheMaster (Jun 12, 2009)

For the typical homeowner the simplest system is usually the best system IMO. The more things added to the the system the more likely its going to breakdown. In 2010 before i bought two tank heaters I'd go with a tankless if at all possible.


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## Don The Plumber (Feb 14, 2010)

I like to put on an inexpensive thermometer on the hot outlet from each heater, especially if they are different manufacturers, or size. This way atleast you can see that you have the same water temp on both to start with. Mostly all those water heater controls are impossible to figure out temp setting, by Warm, Hot, & Very Hot as a temp setting, which will vary on each heater.
I can't believe Sewer Ratz response wasn't to say, "forget it, put in a tankless" LOL


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## smellslike$tome (Jun 16, 2008)

Forget it, put in a tankless.


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