LD1
Epic Contributor
Well in that case, its the little horizontal piece connecting the cold water from the left tank to the hot water on the right tank. and I was mistaken earlier as its the line just ABOVE the gas valve
No Hot Water Heaters over 50 gallons now at Lowes or Home Depot
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Well in that case, its the little horizontal piece connecting the cold water from the left tank to the hot water on the right tank. and I was mistaken earlier as its the line just ABOVE the gas valve
cat fever
Elite Member
What you have stated is why many choose to go in series, it's easier. In parallel the amount of piping needs to be the same going in/out of each water heater. Otherwise you would have uneven flows.
Those of us on wells have built in expansion tanks. (the pressure tank, mine is a 85 gal well X trol ) In my area, the meter for those with city water has a check valve. Hence the need for an expansion tank. Many years ago meters did not have check valves and there was no need for an expansion tank.
LD1
Epic Contributor
Had to draw out flow paths to make sense as it was hurting my head:laughing:
His current flow of water
Using only the right tank. (circled valves need opened, X'ed need closed)
Only left tank (same thing with circled and X'ed valves)
And for parallel, only one valve would need added to prevent the mixing of hot and cold between the two tanks. Closed for parallel, open for everything else
Dont know the science or reasoning behind either setup. Never researched it, But I would think parallel would preform better. Say you have 2 40gallon heaters, total hot water is 80 gallons. So no matter what, you will get 80 gallons before you run out. But then theres the first hour rating and all. Because as you use water, the incoming cold water will start to heat up, and by the time you run the tank empty, you have warmed up some of the water so you get a little more than 80 gallons.
So, on a series system, with 40 gallon tanks, you have to pretty much empty the first tank and start feeding the second tank with colder water before it will start to heat.
Whereas a parallel system, once you use a little hot water off the top, both tanks will fire and be heating. So to oversimplify, if you have a pair of 40's with a 50gal 1st hour rating.......I think the total system 1st hr rating would be more like 50+40 = 90. With parallel I think you would be closer to the full value of 100.
His current flow of water
Using only the right tank. (circled valves need opened, X'ed need closed)
Only left tank (same thing with circled and X'ed valves)
And for parallel, only one valve would need added to prevent the mixing of hot and cold between the two tanks. Closed for parallel, open for everything else
Dont know the science or reasoning behind either setup. Never researched it, But I would think parallel would preform better. Say you have 2 40gallon heaters, total hot water is 80 gallons. So no matter what, you will get 80 gallons before you run out. But then theres the first hour rating and all. Because as you use water, the incoming cold water will start to heat up, and by the time you run the tank empty, you have warmed up some of the water so you get a little more than 80 gallons.
So, on a series system, with 40 gallon tanks, you have to pretty much empty the first tank and start feeding the second tank with colder water before it will start to heat.
Whereas a parallel system, once you use a little hot water off the top, both tanks will fire and be heating. So to oversimplify, if you have a pair of 40's with a 50gal 1st hour rating.......I think the total system 1st hr rating would be more like 50+40 = 90. With parallel I think you would be closer to the full value of 100.
cat fever
Elite Member
Just read the link you provided. I remember talking about this very thing while in plumbing school. While in principle I agree, s still prefer series for the fact (theory) I should only have to deal with one going out at a time. Parallel could have both leaking within a short amount of time.
LD1
Epic Contributor
What would be different about 1 vs two leaking when comparing parallel to series. They both have the same amount of water and same temp running through them.
I would agree that in series, the heating element may fail on the first tank alot sooner than the second whereas parallel would be closer to the same timeframe, but I dont see how the same holds true for leaks/corrosion
cat fever
Elite Member
If he tried to run in parallel the tank on the right would do the lions share of the work. Water will pick the least amount of delta P.
cat fever
Elite Member
The build up of sediment will be more in the first tank and thus require more heat to achieve set point. I understand in many areas electric is what they have. I have dealt mostly with natural gas fired heaters. So, more sediment means more heat means tank leaking sooner. At least that's been my experience.
Zerk
Veteran Member
The flow of water from the well to house or pressure tank is in parrallel. Not quite same system.
Speaking from my bowels, parallel makes sense.
With series the first one may not get used as much. Cold will pump into the tank that loses releases hot water. With city water that may make that one higher pressure???? With well the full tank may have higher pressure.
I could see where in a perfect world or industry you would have Flo control of some kind with 2 tanks.
Speaking from my bowels, parallel makes sense.
With series the first one may not get used as much. Cold will pump into the tank that loses releases hot water. With city water that may make that one higher pressure???? With well the full tank may have higher pressure.
I could see where in a perfect world or industry you would have Flo control of some kind with 2 tanks.
Zerk
Veteran Member
If you are going to pipe in series, you should turn one down. It is acting as a preheater, and wasting money if not needed. If demand is low and in series one will not be running, so cheaper.
Guide to Alternative Hot Water Sources - how to choose among different ways to make domestic hot water
Where hot water volume requirements are high, in addition to installing a single larger-capacity water heater, one can install a several water heaters connected in parallel
Some buildings use water heaters installed in series to handle variations in hot water demand more economically
•When the anticipated hot water demand is low, only water heater #2 may be running.
•When the anticipated hot water demand is high, water heater #1 is turned on as well, doubling the volume of hot water available (if the heaters are of the same capacity in gallons or liters).
•Water heater controls can be adjusted so that the "upstream" water heater, (water heater #1 in our example), is left turned off or perhaps set to a very low temperature. In either of these cases, the upstream water heater or tank functions as a "booster water warmer" reducing the energy use by water heater #2 by pre-warming water entering the active heater#2.
Guide to Alternative Hot Water Sources - how to choose among different ways to make domestic hot water
Where hot water volume requirements are high, in addition to installing a single larger-capacity water heater, one can install a several water heaters connected in parallel
Some buildings use water heaters installed in series to handle variations in hot water demand more economically
•When the anticipated hot water demand is low, only water heater #2 may be running.
•When the anticipated hot water demand is high, water heater #1 is turned on as well, doubling the volume of hot water available (if the heaters are of the same capacity in gallons or liters).
•Water heater controls can be adjusted so that the "upstream" water heater, (water heater #1 in our example), is left turned off or perhaps set to a very low temperature. In either of these cases, the upstream water heater or tank functions as a "booster water warmer" reducing the energy use by water heater #2 by pre-warming water entering the active heater#2.
Zerk
Veteran Member
Do you have the back up set at a lower temp? The back up will not be used as much if, you hot water demand is not always high. Atleast that is what I got from the link I posted.
It does seem to be something that is done both ways.
