# DIY Powered Anode Rod



## sidejobjoe (May 30, 2014)

So having a problem with my hot water smelling like rotten eggs. I replaced the anode rod about a year ago with a pure magnesium one.... add to the fact I have a water softener, you can see the problem

At any rate, looking to replace the magnesium rod with a powered rod. From the looks of the powered rods I've seen, they appear to be very simple devices.  A 3/4" plug with a titanium rod that had a wall wort with 24VDC going from the rod and the ground screwing down to the tank. 

Is that all that is going on here? They cost like $250 (I have an 80 gallon tank). Seems like alot for a simple device and I figure I could make one myself for significantly less. 


Any insight appreciated!


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## sidejobjoe (May 30, 2014)

Oh, I should add... I'm sure there is a resistor in there somewhere to limit the current to a few milliamps. 

As I understand the process, electrons flowing thru the water -> tank -> ground is what is helping prevent the steel from oxidizing. Traditional rods supply electron flow via dis-similar metals (oxidation of the rod), powered ones just run current thru the tank.


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## joecaption (Nov 30, 2011)

Considered having the water tested to see what the real issue is to know how it should be treated?


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## AllanJ (Nov 24, 2007)

You need a screw in plastic plug that fits in the hole that the original anode rod went in and with a smaller hole in the middle that the new anode will go into.

The whole assembly must be replaceable.

At this time I am not sure what voltage is needed but if the kit comes with a 24 volt source, you would not go wrong with that. Most important, the positive terminal goes to the anode, the negative to some metal part making good electrical contact with the tank. I would say that the relief valve is a good location. Ordinarily one of the pipe nipples on top is an ideal place to connect the negative terminal but that will not work with dielectric nipples.

The actual current flow will depend on the purity of the water. While a large current flow is not expected, a resistor is suggested to protect the power supply. A 2500 ohm resistor will limit a 24 volt source to about ten milliamperes.


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## sidejobjoe (May 30, 2014)

AllanJ said:


> You need a screw in plastic plug that fits in the hole that the original anode rod went in and with a smaller hole in the middle that the new anode will go into.


I thought about that... question/concern here is, is it OK to put a plastic(PVC) plug in a hot water tank.... i.e. is it safe? Steel would be work but presents another problem, keeping the rod insulated from the plug (i.e. so it doesn't short to the tank). 

The other issue/problem is making the hole in the plug and the anode rod water tight (under pressure).


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## sidejobjoe (May 30, 2014)

joecaption said:


> Considered having the water tested to see what the real issue is to know how it should be treated?


I am 99% certain the anode rod is the problem. Simply because I replaced it less than a year ago. The "rod" I removed was completely dissolved, just a little wire nub left on the end of the plug/screw (previous owners never replaced it). 

I replaced it with a pure magnesium rod.... and given I have softened water, it didn't smell before and only the hot water smells (it is city water, BTW) -strongly looks like the anode rod is causing the problem. 



Just for the hell of it, I'll build one. Plan is to get a 3/4" PVC plug (CPVC would be better, if I can find it) drill a .125" hole in it and put a .125" titanium rod in it. Then fill the "inside" of the plug with epoxy around the rod. I *think* this will give me a long term water tight seal. 

Since I have D/C transformers laying around the house, it will be a $20 experiment. 

My original question was, are the ones you can buy doing anything special? Trying to figure out why something like this would cost $250.


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## bob22 (May 28, 2008)

How does the transformer remove the "smelly" ions?


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## sidejobjoe (May 30, 2014)

Probably the simpliest explaination is here: http://www.waterheaterrescue.com/Troubleshooting/stinky-water-in-hot-water-heaters.html

But otherwise there are longer ones if you look up impressed current anodes. 

I should also note that I will be pouring H2O2 in the tank while I got the rod out.


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## supers05 (May 23, 2015)

sidejobjoe said:


> Probably the simpliest explaination is here: http://www.waterheaterrescue.com/Troubleshooting/stinky-water-in-hot-water-heaters.html
> 
> But otherwise there are longer ones if you look up impressed current anodes.
> 
> I should also note that I will be pouring H2O2 in the tank while I got the rod out.


Did you try h2o2 first? Apparently that's supposed to work quite well long term until it sits stale. (for verification before you go through all the trouble of this project) 

It's been a long time since I've done chem calcs so I'm quite rusty. I probably be of much help with the power consumption. But you're essentially replacing the naturally occurring electrolytic effect between the annode rod and steel tank. It's better the deposit onto steel then to rip mass from it, an electron at a time. Polarity matters!

For some additional safety, use the power supply on an gcfi plug. That way if something goes weary, then you have something to protect you. Consider bonding the piping, if the code allows, as this will add to that protection. (protect from a fault, then assume a fault will occur) 

Don't forget that electrolysis in water and brine solutions can cause significant issues in stale tanks. I don't know what the commercial solutions do for that problem, if anything at all. 

Cheers!


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## sidejobjoe (May 30, 2014)

So after doing some research, it appears the models you can buy do have some "fancy" electronics in them. Basically they use a potentiostatic current to measure the resistance of the anode -> tank and dynamically adjust the current flow. 

As I understand it, the advantage of this is the tank is not "over protected" which leads to excessive current flow, which creates more H2 gas which in turn reacts with the bacteria to create more H2S gas (and the smell). The reason why magnesium rods more produce this smell more readily in softened water is they more readily give up electrons and the resistance of the softened water is lower, thus more current flow, thus anode rod is consumed more quickly - thus the tank is "over protected". 

The circuit also guarantees the tank is not "under protected". 


Never the less, I am not sure how necessary this circuit is as I wouldn't think the current flow (resistance) would change that much very often once set. I see the need for it for selling a manufactured unit as you have no idea what kind of environment (tank) it will be installed in. So electronically adjusting the current flow is critical. 

My plan is to measure the actual current flow and manually adjust resistance with resistors/potentiometer.... @ 24V you want something around 15mA (so I've read)..... and just keep an eye on it. If it changes often, I'll either fork out the bucks for the professional model or (more likely) try the aluminum/zinc rod. 

The tank I have is somewhat old (over 10 years) so if it fails I won't be too heart broken. But as it is, it seems to be doing well. When I do the yearly draining of the sediment, there is very little. 

I'll post some pics when I get this rig put together......


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## SG44444 (Nov 16, 2016)

Interesting that you are talking about this today, when I was doing a google search for the same information! 
I wanted to say that, if you need a steady current and the supply is DC, it is fairly trivial to build a constant current source or sink out of 2 transistors and a few resistors, or with an LED and a transistor and resistor. This type of circuit will adjust the voltage output to meet the current set point, up to the point where the resistance is too large to overcome with the voltage used (which is called "going out of compliance"). 
Did anyone determine what the polarity and current should be?


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## SHR Plumber (Aug 20, 2013)

Start by setting aside the powered rod idea. You need an ALUMINUM anode rod. Relatively cheap, readily available and almost always cures your smell problem.


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## sidejobjoe (May 30, 2014)

SG44444 said:


> Interesting that you are talking about this today, when I was doing a google search for the same information!
> I wanted to say that, if you need a steady current and the supply is DC, it is fairly trivial to build a constant current source or sink out of 2 transistors and a few resistors, or with an LED and a transistor and resistor. This type of circuit will adjust the voltage output to meet the current set point, up to the point where the resistance is too large to overcome with the voltage used (which is called "going out of compliance").
> Did anyone determine what the polarity and current should be?


Positive on the rod and negative on the tank.... current something like 15 mA


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## sidejobjoe (May 30, 2014)

Ya know... That's what I've read but now I am questioning it. Given this is an *anode* rod seems the current should flow from the rod to the tank and thus negative would be on the rod and positive on the tank. 

Going to have to do some more digging now


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## sidejobjoe (May 30, 2014)

This diagram suggests positive at the anode and negative at the tank..... 

http://www.mtgree.com/product/html/?13.html

This also jives with a couple of other diagrams I've seen on the topic. 

It also makes sense from the perspective we are trying to add electrons to what we want to protect, the tank. 

I've also read in some various book snippets that a current as low as 5mA is sufficient. More current is not better as it will cause the lining of the tank (the glass/porcelain) to separate from the steel (see: cathodic disbonding). So between 5mA and 10mA is probably about right. 

No matter what, having a regulated current will be superior than a sacrificial anode. The reason you get the rotten egg smell is because too much current is flowing and creating H2 gas. This is why an aluminum rod is less susceptible to the problem because it is less reactive than magnesium and thus less current flow. However, the problem I have is I have softened water so it is less resistive thus more current flows and more H2 gas. 

So this is how I understand the problem. There certainly is alot to cathodic protection systems and I am an extreme amateur at best . 

I am pretty sure I'm right on the polarity, if not I hope someone will correct me.... cause pretty sure having it backwards will speed up corrosion .


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## sidejobjoe (May 30, 2014)

So I got my powered anode installed last night and I sanitized the water heater with some H2O2 (a cup of 35% seemed to do the trick). 

I built a pretty simple circuit using an LM317 as a constant current source. You can read all of the details about that here: http://www.bristolwatch.com/ccs/LM317.htm

There are many ways to do it but I used the LM317 simply because I had one laying around. 

In addition, there is a 300 ohm ish resistor on the output to limit the current and more importantly drop the voltage so the LM317 doesn't have to do all the work. 


I get a steady 12mA measured between the tank (cathode) and the anode. I'm still confused by the polarity thing but seems all the ones you can buy are positive at the anode. I suspect the confusion I've seen has to do with the old thing with the mistaken belief that DC current flows from positive to negative. This goes back quite a while and is everywhere... e.g. your car. 


I decided on 10-15mA because I have an older and larger 80 gallon tank. 


The good news is the smell is gone (thanks to the H2O2) time will tell if it comes back with the powered anode. 


(I would post a picture but doesn't look like you can do attachments on this site).


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## Corro-Protec (Nov 25, 2019)

sidejobjoe said:


> I am 99% certain the anode rod is the problem. Simply because I replaced it less than a year ago. The "rod" I removed was completely dissolved, just a little wire nub left on the end of the plug/screw (previous owners never replaced it).
> 
> I replaced it with a pure magnesium rod.... and given I have softened water, it didn't smell before and only the hot water smells (it is city water, BTW) -strongly looks like the anode rod is causing the problem.
> 
> ...


I know that this discussion is already 3 years old, but it is still very relevant today. You are very resourceful to have made a imposed current anode yourself and your calculation of milliamperes seems correct. :biggrin2: The only way to check that your system is functional and protects your tank would be to test the polarization of your tank with a reference electrode. Did you use only a titanium rod to make the anode? :glasses:

As for the rotten egg smell, it can be created either by a reaction between your water and the magnesium anode, or by Sulfur-Reducing Bacteria. If the odor comes from the bacteria, the forced-current anode solves the problem by lowering the pH of the water, making the medium too acidic for the survival of this bacteria.

There are less expensive solutions today than CerAnode. Our Corro-Protec anodes sell for $ 119 and have a 20 year warranty. 

Also, our powered anode is covered with MMO : 

ELECTROCHEMISTRY AT AN MMO ANODE (From : https://www.onepetro.org/conference-paper/NACE-07045)

'' There are many oxidation reactions that can occur on the surface of an anode. These include metal oxidation, oxygen evolution and chlorine evolution. The reaction that dominates is largely determined by the anode material and the electrolyte in which it operates.1 

For MMO coated titanium anode, metal oxidation is nearly insignificant, since the anode surface is fully oxidized prior to being energized. MMO anodes are a composite structure consisting of a valve metal (typically titanium) substrate covered by an electrocatalytic film of noble metal oxide. These anodes are characterized by very little dissolution of the metal oxide and uniform wear rates. The low consumption rate of the electrocatalytic layer of these MMO anodes operated at the recommended low current densities of CP applications has been demonstrated by lifetimes of over 20 years for underground, seawater and concrete installations. For soil, concrete and freshwater applications where chloride ions are either not present or are present in low concentrations, the evolution of oxygen will be the dominant reaction: (available in full paper) 

This water decomposition reaction produces an acid environment around the anode. When MMO coated titanium anodes are used for cathodic protection, they are operated at significantly higher current densities than most other impressed current anodes making their resistance to acidic conditions an extremely important characteristic. The MMO anode is designed to tolerate an acidic environment. The titanium valve metal substrate will form a protective oxide film if there is any defect in the electrocatalytic layer. Assuming the damage to the electrocatalytic coating is not significant, the remaining electrocatalytic coating will continue to support the current required for cathodic protection. ''


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## Mr. Mint (Dec 4, 2020)

sidejobjoe said:


> So having a problem with my hot water smelling like rotten eggs. I replaced the anode rod about a year ago with a pure magnesium one.... add to the fact I have a water softener, you can see the problem
> 
> At any rate, looking to replace the magnesium rod with a powered rod. From the looks of the powered rods I've seen, they appear to be very simple devices. A 3/4" plug with a titanium rod that had a wall wort with 24VDC going from the rod and the ground screwing down to the tank.
> 
> ...


Be advised that municipalities purposely provide hard water to prevent water from picking up dangerous metals from the plumbing system and underground pipes. By using a water softener, you risk having the soft water pull unwanted lead and other unwanted metals from joints, fittings, and fixtures. My best suggestion is to eliminate the water softener for safety sake. This will probably solve the hydrogen "rotten egg" smells as well. It's all in the water chemistry.


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## lenaitch (Feb 10, 2014)

Mr. Mint said:


> Be advised that municipalities purposely provide hard water to prevent water from picking up dangerous metals from the plumbing system and underground pipes. By using a water softener, you risk having the soft water pull unwanted lead and other unwanted metals from joints, fittings, and fixtures. My best suggestion is to eliminate the water softener for safety sake. This will probably solve the hydrogen "rotten egg" smells as well. It's all in the water chemistry.


At the risk of extending a four year old thread, I was always under the impression that the water municipalities provided was determined by where they draw it from. If the source is naturally soft, how do they 'harden' it? Other than persons who may be sensitive to sodium levels, how is softened water unsafe?


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