Series water heater questions

[Shobuddy]

We moved into a new construction home a few months ago and have two electric water heaters setup as a series in the basement. Since its just me and my wife, we don't' use need both the heaters so I turned off the upstream heater and the downstream heater has been satisfying our demand just fine. I have a few questions regarding this setup.

1. Is there a downside to leaving the upstream heater off as far as damage to the heater or any other issues?
2. I want to setup a fail safe so is there a way to set the system where if the downstream heater fails, I can simply switch to the upstream? I want to do this w/out switching to the parallel configuration. What would the approximate costs be?

Picture of the heaters is attached.

 

[Smooky]

You would need 6 shut off valves. One on each tank inlet and outlet. You would need to pipe accross the top of the heater and put a shut off between the hot and cold of each tank. That way you could go through them both or only one or none.

 

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[Reach4]

1. Is there a downside to leaving the upstream heater off as far as damage to the heater or any other issues?
2. I want to setup a fail safe so is there a way to set the system where if the downstream heater fails, I can simply switch to the upstream? I want to do this w/out switching to the parallel configuration. What would the approximate costs be?

I am not a plumber. With chlorinated city water, I don't see a problem with just turning off the breaker on the first WH. Even with non chlorinated water, it would probably fine too. I was thinking (over-thinking) that the heat can inhibit most pathogenic bacteria. But if you sanitize, there should not be any to grow anyway.

 

[Shobuddy]

You would need 6 shut off valves. One on each tank inlet and outlet. You would need to pipe accross the top of the heater and put a shut off between the hot and cold of each tank. That way you could go through them both or only one or none. View attachment 36769

By my count that comes to 4 valves for two heaters, am I missing something? Also, I guess what you're describing is pretty much a parallel system, right? Do you know approximately how much a plumber would charge to do this?

 

[Shobuddy]

I am not a plumber. With chlorinated city water, I don't see a problem with just turning off the breaker on the first WH. Even with non chlorinated water, it would probably fine too. I was thinking (over-thinking) that the heat can inhibit most pathogenic bacteria. But if you sanitize, there should not be any to grow anyway.

Thanks for the response, I'm on public water so definitely have Chlorine. What do you mean by "sanitize"?

 

[Reach4]

Thanks for the response, I'm on public water so definitely have Chlorine. What do you mean by "sanitize"?

That is something that people with wells do. It is a shock chlorination. I figure to do it about every 2 years or so, but I do an intense sanitizing, and I have a deep well with full casing. Conditions vary.

With chlorinated water, the chlorine levels are lower, but the chlorine is there all of the time.

So no extra valves, needed IMO. The breakers are already there. Extra cost zero.

 

[Smooky]

By my count that comes to 4 valves for two heaters, am I missing something? Also, I guess what you're describing is pretty much a parallel system, right? Do you know approximately how much a plumber would charge to do this?

If you look at that diagram I provided you will see 3 shut off valves for each tank. So there would be 6 not 4 valves for your two tanks. For a parallel system it would need to be plumbed completely different. The diagram that I provided is for tanks in series. The valves allow either of the tanks to be bypassed if you choose.

 

[Master Plumber Mark]

The cpvc on top of the heater looks pretty crappy in my opinion but
suppose it works ok...

I think that you are worrying about it too much....
I dont see a thermal expansion tank on the units and I dont know if
the units are installed in pans or not.... I would be more worried about
one of them flooding the hell out of the basement some day..... I assume that the t+p
lines are piped to a nearby drain??.

If it were mine I would probably throw some blankets on both of the heaters
to conserve a shitload of energy

If it were mine I would just turn down the first incomming heater down to 110
and use the second heater to really heat the water......

if you completely turn off the first heater it will start to do like an aquarium and get
very nasty on the bottom over time....

I would leave them alone and only worry about it if and when one of them goes bad
which could be more than a decade from now..
(you might already be dead by then so dont fret over this)

all you really need to do is divert one or the other would be a couple of shark bite male
adapters that would go on the inlet and the outlet lines and a few 24 inch flex connectors
to tie back into the good working heater......

If you were to install all that bypass cpvc system on top of that
heater it will look like hell. The SS flex lines can be seen on the rheem water heater in the picture......

....