Anode of the H.W.S.

JayDee · Guru

Anode of the H.W.S.

JayDee · Guru

Jay&Dee here.
Silly me, I just did a search and found a lot of info re Anode and HWS,
Jay&Dee

03_troopy · Guru

Always good to post a reminder mate.
Cheers

deverall11 · Guru

On that note JayDee, depending on what sort of water ends up in your HWS dictates how often you check your anode. If, like we are, you are on the road 24/7 your anode will decay at a different rate. If you use filters this will take longer. If you do not use filters and are in WA, you anode could decay completely in a mater of weeks.
Larry

_wombat_ · Master (of Mischief)

deverall11 wrote:
On that note JayDee, depending on what sort of water ends up in your HWS dictates how often you check your anode. If, like we are, you are on the road 24/7 your anode will decay at a different rate. If you use filters this will take longer. If you do not use filters and are in WA, you anode could decay completely in a mater of weeks.
Larry

sorry to disagree, we live in WA and have no major problems with anode's, I did have one last 2 years at one stage but do pull them out and check each year.

pws25 · Senior Member

My van was in storage for a cuppla yrs, then decided to go to Tassie... hws. sprung a leak over there, $ 1250!! so yes, VERY important check anode! also, if not using van/m/home for a few mths drain the hws........

I write on the inside of the hws ''door '' when last checked, & leave a spare anode & the socket to undo tucked in there....

_wombat_ · Master (of Mischief)

pws25 wrote:
My van was in storage for a cuppla yrs, then decided to go to Tassie... hws. sprung a leak over there, $ 1250!! so yes, VERY important check anode! also, if not using van/m/home for a few mths drain the hws........
I write on the inside of the hws ''door '' when last checked, & leave a spare anode & the socket to undo tucked in there....

that's a good idea about writing on the inside of the door, do you mind if I pinch that?

Wizardofoz · Guru

is the anode a standard size or do they vary accoring to brand and caravan size?

_wombat_ · Master (of Mischief)

I think some are longer, just go to a caravan shop and tell them what van you have and they should know which one to give you, or you can take yours out and if it does not need replacing put it back in.

Some of the newer vans do not have anodes

pws25 · Senior Member

Yep , ya can pinch that Wombat.... wonder how the newer vans combat electrolysis? [ spelling ]...

deverall11 · Guru

_wombat_ wrote:
sorry to disagree, we live in WA and have no major problems with anode's, I did have one last 2 years at one stage but do pull them out and check each year.

Wombat, don't want to harp on this point, but here are a couple of facts from personal experience.

1) WA is the only state that has anodes in their HWS at home. Should you feel the need to replace such item, you are looking at approx $150.

2) In NSW, HWS can last 20 - 25 years before needing to be replaced. In WA, if you do not replace the anode you are looking at 10 - 12 years.

3) No other states other then SA, has calcium build up in retic systems that require constant attention.

Regards,

Larry

brian · Guru

deverall11 wrote:
_wombat_ wrote:
sorry to disagree, we live in WA and have no major problems with anode's, I did have one last 2 years at one stage but do pull them out and check each year.
Wombat, don't want to harp on this point, but here are a couple of facts from personal experience.
1) WA is the only state that has anodes in their HWS at home. Should you feel the need to replace such item, you are looking at approx $150.
2) In NSW, HWS can last 20 - 25 years before needing to be replaced. In WA, if you do not replace the anode you are looking at 10 - 12 years.
3) No other states other then SA, has calcium build up in retic systems that require constant attention.
Regards,
Larry

I have to offer some corrections to the above points.

1. ALL hot water tanks that are made of ferrous metal with a glass lining (which is the vast majority of tanks) have a sacrificial anode, it doesn't matter which state or which country that you live in.

The only ones that don't have an anode are the unlined stainless steel tanks.

2. You would be very lucky indeed to get 20 years out of an anode, in fact, if you were to find a tank with the anode in good condition at that age, you would question the equipotential bond of the anode to

the tank, If you had a lined ferrous tank with no anode it would last maybe 5 years at most in any of the states of Australia.

Most manufacturers recommend 5 yearly anode replacements for their ferrous tanks.

3. The purpose of a sacrificial anode has nothing to do with controlling Calcium build up, although Calcium etc. accumulating on the anode can reduce its effectiveness.

Incidentally, I have a tee and a drain tap installed in the cold water inlet pipe between the hot water tank and the non return valve.

When I am not using the van for a little while, I simply open the tank, pull the pressure relief valve and the tank empties.

The Suburban tanks have a cold water diffuser on the cold inlet which goes right to the bottom of the tank, and so almost all of the water is siphoned out below any internal fittings in the draining process.

No water in the tank equals no corrosion and no anode deterioration either.

-- Edited by brian on Tuesday 14th of January 2014 02:27:07 PM

Bryan · Guru

Thank goodness mine doesn't have an anode. One less thing to worry about.

brian · Guru

Bryan wrote:
Thank goodness mine doesn't have an anode. One less thing to worry about.

Just be aware that hard water as is found in many rural areas can be fatal to stainless steel hot water tanks as it strips away the passive layer that would normally protect the SS.

laurieoz · Senior Member

I guess it depends on the grade of stainless steel - there are many that react different

Do you have a link to this erosion in stainless tanks of HWS in MH?

I was a Metallurgist but now retired forget most of the reactions with SS

brian · Guru

laurieoz wrote:
I guess it depends on the grade of stainless steel - there are many that react different
Do you have a link to this erosion in stainless tanks of HWS in MH?
I was a Metallurgist but now retired forget most of the reactions with SS

It will not be hard for you to find plenty of data on this. Just Google things such as :- stress corrosion cracking, crevice corrosion, pitting corrosion, depassivation, galvanic corrosion etc. etc. or even just stainless steel corrosion. You will get a plethora of reading material.

The passivation layer that forms on stainless steel, and which gives it its corrosion protection is at most only 150 millionths of a centimetre thick, that's way less than the thickness of a hair, it doesn't take too much to penetrate that and begin the corrosion process especially in a low free oxygen environment, the prospect of depassivation attack doubles with every 10°C rise in temperature, so in a hot water service with aggressive water quality (bore water containing dissolved metals or water having a low ph as is often the case with rainwater straight from tanks) or heavily chlorinated water, a stainless tank can be in jeopardy.

While you are doing the reading bit check out some of the exclusions that the manufacturers of Stainless steel hot water services put into their warranty conditions.

Many of the water quality limitations are easily exceeded in some of our rural areas where total dissolved solids and hardness levels that aalone can be around 3 times the warranty limits and numerous rurarea have hardness that is also above the warranty limits

I'm not saying that SS is not a good product for a hot water tank, but it is not without its pitfalls, no pun intended.

laurieoz · Senior Member

Hi Bian

My motor home is 15 years old - I looked for the anode when I purchased it 5 years ago and found out it was a SST tank without anode

The only problem I have read about with my system is failure of the "O" ring seals that I have not had yet.

Should I consider any preventive maintenance with my SST tank?

-- Edited by laurieoz on Tuesday 14th of January 2014 08:30:10 PM

pws25 · Senior Member

Well, ive,learnt something tday, I was assuming my experience in a marine enviroment re anodes, was the same as hws in caravans?? [ electrolysis ] I was always replaceing anodes at every lift out.. on the shaft, keel & rudder & renewing the earth straps...

So the caravan situation is related to water quality??as opposed to ''stray'' electricity?... It sounds like the cuppla previous posters know what they are on about....

laurieoz · Senior Member

If your anode in the marine system is eroded then it is saving other parts of your boat - that is why they are attached to the system.

My HWS is SS and not surround by salt water so I guess it is a different electrolysis system

brian · Guru

laurieoz wrote:
Hi Bian
My motor home is 15 years old - I looked for the anode when I purchased it 5 years ago and found out it was a SST tank without anode
The only problem I have read about with my system is failure of the "O" ring seals that I have not had yet.
Should I consider any preventive maintenance with my SST tank?

-- Edited by laurieoz on Tuesday 14th of January 2014 08:30:10 PM

About the only maintenance that you need do is to ensure that there is no gunk build up in the bottom of the tank. This will normally be a mixture of minerals and metal that have leached or settled out of the water.

Crevice corrosion and pitting can occur at the juncture of the water and the gunk due to both the abrading of the passive layer from the surface of the SS and a lack of free oxygen to allow that passive layer to reform.

If used in areas with poor water quality, it's a good idea to flush the tank with clean water as soon as possible.

brian · Guru

pws25 wrote:
Well, ive,learnt something tday, I was assuming my experience in a marine enviroment re anodes, was the same as hws in caravans?? [ electrolysis ] I was always replaceing anodes at every lift out.. on the shaft, keel & rudder & renewing the earth straps...
So the caravan situation is related to water quality??as opposed to ''stray'' electricity?... It sounds like the cuppla previous posters know what they are on about....

If you don't want to know about cathodic protection, read no further as it is a bit long winded. I seem to do that a lot. blankstare

Corrosion as experienced in boats or hot water tanks, or cars or steel structures or pipelines is all electrical in nature.

You could call it stray currents in so far as they are not being adequately controlled if corrosion is occurring.

All electrolytic action requires an electrolyte (that's the acid in the battery) before it can happen. No electrolyte equals no action just as in a battery.

Mineralised water is a very good electrolyte, and the more mineral content in the water, the better it conducts, and the more helpful it is to corrosive elements.

This is where water quality comes into it, sea water is an extremely good electrolyte.

When your car develops small rust spots, what you are seeing is a very small galvanic cell, essentially a small battery, where minute impurities in the steel form the positive and negative plates, and a bit of dust and moisture form the electrolyte, and like all good batteries, a current flows between those plates and they slowly corrode away.

So how does the anode help?

A carbon steel water tank will corrode very easily unless it is somehow kept isolated from the electrolyte (the water). This is achieved by lining the inside of the tank with, usually, glass or ceramic material.

Now this lining is not 100% perfect, it may have small defects (called "holidays" in the industry) and it will also be incomplete where there are pipe penetrations, electric elements, gas heating tubes etc.

So to stop corrosion from occurring at those exposed locations, a sacrificial anode is fitted into the tank and electrically connected to the steel of the tank. It is called a sacrificial anode because it is made of a metal which is less noble than the metal which you wish to protect and so will sacrifice itself in favour of steel tank.

If you care to Google "galvanic scale or Galvanic series" you will see a list of metals and where they appear in ranking.

A simple explanation of how it works is that the 2 dissimilar metals (in our case Magnesium and steel) set up a voltage difference between them and therefore a current will flow just as in a battery.

The direction of this current flow will be out of the anode - through the electrolyte and into the exposed steel and then back to the anode via the solid connection.

Where the electrons (which are just very small atomic bits of the anode) leave the anode it will gradually erode, and some of the anode will be carried through the water and deposited on the steel thus ensuring that the steel does not corrode.

Now obviously we could use this method to protect an unlined tank, but the anode would have to be immense.

You will note when you remove an anode that it is normally more eroded at the nut end and this is because of the closer proximity of the electric element and gas heater tube and so the greater current flows from the anode in this region.

The main reason that the anode in your van tank erodes more rapidly than the one at home is due to the relatively larger surface area of uninsulated metal in the tank (gas heater tube etc) as compared to anode size.

End of waffle, hope it explains a bit about the process.

johnq · Guru

Good, while on rust, how do systems like this protect a fourby on a beach? See here,

http://www.erps.com.au/

http://www.ultimate4wdequipment.com.au/d130-91/couplertec-electronic-rust-protection/

pws25 · Senior Member

THANKYOU Brian for that , it was easy to understand.I never knew that 2 metals , in water ,created an electrical current..I was thinkin, maybe disconnecting batteries while not using van would stop that.

But, thinkin back to my last $$$$ episode, the van was in storage for a cuppla yrs [ no battery ] AND the hws. still full o water, 6 wks. into our trip the hws. sh.t itself!.........

Thanks again for the info...surprising how many people don't know bout the anode thingy............

JayDee · Guru

Well I have just installed the new anode after I flushed out the tank and removed all the white gunk etc. Ended up with a free shower as I stood in front of the tank when I released the hose and the water came gushy out at 100 kph.
So now we can enjoy our " new " HWS.
Jay&Dee

brian · Guru

johnq wrote:
Good, while on rust, how do systems like this protect a fourby on a beach? See here,

http://www.erps.com.au/

http://www.ultimate4wdequipment.com.au/d130-91/couplertec-electronic-rust-protection/

Best way to answer that is to google "electronic rust prevention" and see how many independent tests you can find that support the purveyors' claims for them.

Their advertising has been banned as fraudulent in many parts of the U.S.

Some early claims for them were that they worked on the cathodic protection principle that I explained earlier, but after having been well and truly hosed down with that approach, most now claim that it works on an undisclosed patented secret method involving capacitive coupling or electrostatic magic which no real scientist has yet been able to replicate.

Some of them claim to use the paint as a transport medium for electrons to protect the underlying metal, but the fact is that if the paint is in good order, moisture won't get in and rust won't happen.

If the paint is not in good order as is generally the case under your car due to stone damage etc., then how is the other method going to work anyway.

Most of them claim no warranty protection against surface rust and if you read my bit about that earlier you will see that it is basically impossible to prevent that from occurring by any means other than keeping the moisture out.

johnq · Guru

Brian,

Thank you.