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Join Date: Jan 2011
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Hot Water Tank-Electrolysis

11/30/2012 2:53 PM

thanks for all the good advice on selecting a hot water system. i decided to go with a 30 gallon electric unit. i have acidic water. other than replacing the anodes every few years, will grounding the tank prevent electrolysis? i have rubber plumbing and only an electrical ground attached to the outer steel shell .

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#1

Re: Hot Water Tank-Electrolysis

11/30/2012 3:31 PM

What other grounding would you do?

Anodes?

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#2
In reply to #1

Re: Hot Water Tank-Electrolysis

11/30/2012 3:48 PM

i'm thinking about grounding the tank. the tank shell [grounded] is insulated from the tank and the plumbing.

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#3
In reply to #2

Re: Hot Water Tank-Electrolysis

11/30/2012 3:52 PM

And the tank is isolated?

What do you suppose the manufacturer was thinking? What possible reason could the manufacturer, after reviewing with his legal team regarding culpability of omission, have for not grounding the tank?

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#4
In reply to #3

Re: Hot Water Tank-Electrolysis

11/30/2012 3:58 PM

the tank would would be grounded if i ran copper plumbing. currently the plumbing is rubber. i haven't spoke to there legal team.

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#5
In reply to #4

Re: Hot Water Tank-Electrolysis

11/30/2012 5:14 PM

It would be pretty weird for the manufacturer to go through the trouble of elecrically isolating the shell from the tank,just to have these grounded separately.

Do you believe the heating elements, power and control components are isolated from the tank, or from the shell?

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#7
In reply to #5

Re: Hot Water Tank-Electrolysis

11/30/2012 5:43 PM

the tank shell is completely isolated from the other electrical components. the ground going to the tank shell will prevent an electrical shock by kicking the breaker. the tank, on the other-hand might be grounded through the water. the heating elements are both 220v that screw into the tank top and bottom. all grond wires are connected to the tank shell.

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#9
In reply to #7

Re: Hot Water Tank-Electrolysis

11/30/2012 8:23 PM

I'm confused....you wrote 'tank shell', twice.

Are you refering to the metal which forms the tank? ...Or are you refering to the outermost metal which protects the insulation?

.

I would gamble that the metal on your water heater has good electrical contact. A couple related ideas give me confidence in this.

1. Leaving an ungrounded isolated chunk of metal on a piece of electrical equipment creates a situation where charge could accumulate. This can lead to a whole range of problems, up to human injury, since ungrounded isolated machinery makes situation possible where a person is shocked but no ground fault is seen.

2. If there were some benefit to electrically isolating some chunk of the water heater, it wouldn't be something the manufacturer could depend on remaining long, with the dust, moisture and close proximity of the grounded and (theoretically) ungrounded metal.

3. The screws that hold the metal cover in place are probably steel sheet metal screws... woudn't the sheet metal they attach to be grounded to the tank?

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#12
In reply to #9

Re: Hot Water Tank-Electrolysis

12/02/2012 3:58 PM

yes and no.the 220v leads connect to the heating elements via two thermostats that are not grounded to the inner tank. the ground is attached to a screw on the outer most shell. the inner tank [water tank] is electrically isolatated from the outer tank shell by styrofoam insulation.

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#6

Re: Hot Water Tank-Electrolysis

11/30/2012 5:32 PM

Isn't there a green ground terminal for the incoming power safety ground (the bare copper wire)? AFIK that should ground all exposed metal surfaces.

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#8
In reply to #6

Re: Hot Water Tank-Electrolysis

11/30/2012 6:59 PM

yes there is. it was connected to the tank shell

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#10

Re: Hot Water Tank-Electrolysis

12/01/2012 3:17 AM

Electrolysis is good; it keeps hair from growing in your tank.

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#11

Re: Hot Water Tank-Electrolysis

12/01/2012 12:23 PM

You mention acidic water...if the acidity is due to carbon dioxide in the water, you could treat this simply with contact through a limestone (pebble) bed....and even if the water has free mineral acidity (typical not safe for human consumption)...the same contraption will take care of much of this. There are a number of water treating companies that sell the equipment needed. I take it you are not on a public utility water supply.

There is nothing wrong with the use of a zinc or magnesium anode inside a water heater tank, but with acidic water, the anode will last a much shorter period of time, and may in fact release hydrogen into the water.

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#13
In reply to #11

Re: Hot Water Tank-Electrolysis

12/02/2012 7:14 PM

you've made a few good points. i'm concerned with electrolysis as it applies to grounding the storage tank. there is no ground wire connected to the tank, only the outer shell [the outer enclosure]. it is insulated from the storage tank.

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#14
In reply to #11

Re: Hot Water Tank-Electrolysis

12/03/2012 3:36 AM

As for sacrificial anodes, Magnesium is preferable to zinc.

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#15
In reply to #14

Re: Hot Water Tank-Electrolysis

12/03/2012 9:18 AM

Except you didn't mention why...magnesium is certainly a higher tox threshold. Zinc is less active (however neither of them will last any time in acidic water).

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#17
In reply to #14

Re: Hot Water Tank-Electrolysis

12/03/2012 10:54 AM

Just to keep the record straight , the reason that magnesium anodes are preferable in hot water tanks has MORE to do with the reversal of polarity between iron (steel) and zinc at elevated temperatures.

This was discovered following the introduction of the automatic dishwasher.

Temperatures on water-heaters were typically turned-up a bit to the high-side when a dishwasher was added to the kitchen ... and, when tanks started failing prematurely, it was learned that at those elevated temps, steel would become anodic with respect to the zinc, and the tanks corroded.

In the marine/water environments, zinc anodes (more often than not alloyed with aluminum and indium nowadays) are preferable in salt-water environments, while magnesium, with its higher potential (being more electronegative), is used in fresh-water environments, in order to deliver sufficient cathodic current to the structure.

And [edit here] --- "No", grounding the tank will not in any way-shape-or-form either increase or decrease the potential for local cell corrosion to occur on the tank itself, OR for galvanic corrosion to occur between the tank and any plumbing (whether it were copper or steel piping, or rubber/plastic, as mentioned).

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#16

Re: Hot Water Tank-Electrolysis

12/03/2012 9:21 AM

I think the grounding you are referring to is electrical ground (1) to prevent any short from leaving a high potential on the outer sheath of the tank and electrocuting someone in the event of electrical heater failure/tank failure, or (2) to prevent sparks from causing inadvertent gas ignition in the case of a gas leak nearby (especially for water heaters placed in enclosure with gas furnace).

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