Check your HW heater for an anode!

[JayArr]

We bought this trailer in the spring of this year. It's a 1992 and in decent shape, the inside had all been painted, reupholstered and spruced up. New floors etc. We took it on a one month trip across the country and had a blast.

I noticed while winterizing it that there was no anode rod in the water tank so I bought and installed one.

I think I was twenty eight years too late!

While replacing the butyl plumbing with Pex I noticed that the insulation and cardboard like surround on the water tank was always wet. At first I thought it was from spillage when I cut the lines out to replace them but two weeks later it was still wet. When I dug into the problem a horrible reality set in.

The tank had rotted out from the inside and was leaking water at a very slow rate. This explains why our water pump would periodically turn on for a brief moment about every hour.

The whole front corner of the trailer was rotten. After removing the HW heater the floor under it came out in my hand as broken crumbling debris. The sill plates, floor joists and some of the wall structure in the front was all shot. I spent the entire weekend pulling the siding off and re-framing the front left corner and then putting it all back together.

So... Check your water heater! If it doesn't have a sacrificial anode put one in. If the previous owner had spent $20 I wouldn't have had to spend my entire weekend re-framing the trailer.

 

[NY_Dutch]

What make is your water heater? Suburban heaters need an anode rod, Atwood heaters do not.

 

[Roy M]

What a mess! ( I repaired water damage the nose of a fiver, knew it was there when we bought the unit. I won't do it again.

 

[lynnmor]

So... Check your water heater! If it doesn't have a sacrificial anode put one in.

How often do you change the one in your house?

 

[Deano2002]

well you are good to go now ) surprised you have real plywood floors, new ones have strand/chip board

 

[JayArr]

I don't know why anyone would say that an anode isn't needed in an aluminum tank. Perhaps it was something the marketing department at Atwood dreamed up to make their water heaters look more favorable than the Suburban... but look at the pictures.

That tank corroded from the inside out leaked water at a rate that was undetectable for what I think was years and destroyed the wooden framework around it. The Atwood tanks are aluminum so you might be convinced they don't need an anode but here I am with a corroded tank and a rotten corner in my trailer and I think an anode would have saved all that.

Take a look at the picture of the tank, the grey areas are where the corrosion is coming through from the inside, I'll cut it open when I have time but I bet the wall thickness in the grey areas is minimal. Aluminum corrodes, not as fast as iron but it still corrodes.

Magnesium is more active than aluminum, it has an electrochemical potential of -2.70 as opposed to Aluminum which is -2.31. The magnesium will oxidize first protecting the aluminum tank.

If you don't want to put an anode in your tank because it's an aluminum Atwood that's your prerogative, it's your trailer you get to decide. But, again, look at those pictures, the magnesium rods are less than $20.

I change the one in my house every three years, it's usually not completely shot but I don't see a reason to wait since they are cheap.

 

[Tom55555]

I drain my hot water tank meaning removing the anode about every month. I will also take my finger and rub the treads to make sure they are clean. A new anode is only about ten bucks and they can last 5 years.

Regarding my house, I'm to code, so if my hot water tank leaked it goes into a pan and then to the drain.

 

[Rene T]

I don't know why anyone would say that an anode isn't needed in an aluminum tank. Perhaps it was something the marketing department at Atwood dreamed up to make their water heaters look more favorable than the Suburban... but look at the pictures.

That tank corroded from the inside out leaked water at a rate that was undetectable for what I think was years and destroyed the wooden framework around it. The Atwood tanks are aluminum so you might be convinced they don't need an anode but here I am with a corroded tank and a rotten corner in my trailer and I think an anode would have saved all that.

Take a look at the picture of the tank, the grey areas are where the corrosion is coming through from the inside, I'll cut it open when I have time but I bet the wall thickness in the grey areas is minimal. Aluminum corrodes, not as fast as iron but it still corrodes.

Magnesium is more active than aluminum, it has an electrochemical potential of -2.70 as opposed to Aluminum which is -2.31. The magnesium will oxidize first protecting the aluminum tank.

If you don't want to put an anode in your tank because it's an aluminum Atwood that's your prerogative, it's your trailer you get to decide. But, again, look at those pictures, the magnesium rods are less than $20.

I change the one in my house every three years, it's usually not completely shot but I don't see a reason to wait since they are cheap.

So I guess you?re telling us that your tank is a Atwood. Is that right? This is a 28 year old tank.

The reason Atwood does not need a anode is because the tank is aluminum clad. That means that it has a special coating that is not susceptible  to corrosion like the non cladded tank Suburban has.

 

[JayArr]

I downloaded the Atwood manual and you are partly correct Rene, the Atwood is coated with a 15% coating of pure aluminum/zinc.

It is incorrect to say that the coating is not susceptible to corrosion. In fact the opposite is true.

This seems to be an urban myth that needs to be shown the light of day.

The manual starts by saying that galvanic corrosion may cause pinhole leaks that will cause the tank to fail. The document says that the tank is the anode and it gradually sacrifices itself and particles of aluminum are carried away with the water flow. It also says that the coating is "anodic" and works like an anode rod but will last much longer.

Atwood is deliberately vague about how long the coating will last, they say it will last "much longer" than an anode rod but they seem to allude to the idea that an anode rod needs to be changed once or twice a year. So... how long is "much longer" than a year? Does the coating last 5 years? 10 years? The warranty is only two years so who knows. It certainly doesn't last forever.

During the early years adding an anode rod would probably be duplicative and unnecessary. But at the same time it wouldn't hurt. If if corrodes it's saving the tank.

At the point that the pure coating has been depleted by years of galvanic reactions the structural tank itself becomes the anode and it starts to corrode. At this point an anode rod would be greatly helpful. Magnesium in particular would become the anode saving the structural tank from corrosion.

Jeff

 

[lynnmor]

Thank you JayArr, finally someone who gets it.  I've pointed out the fact that the tank will give up material a number of times over the years.  Folks will always go for more convenience and no parts replacement.

The Suburban has a glass coating, so the anode rod is there to protect the connection points where the glass has incomplete coverage.

 

[Gary RV_Wizard]

I don't think we will convince JayArr that his 28 yo tank died primarily of old age rather than lack of an anode.

I can see where a replaceable anode might be more effective where the water is really caustic. Afterall, the aluminum cladding of the Atwood isn't going to last forever if the water is eating away at it for 20+ years. But for 99.999% of owners, the Atwood tank will have a long and healthy life with no anode. In fact, Atwood says that installing one will void its warranty.

 

[JayArr]

Maybe the takeaway here should be that if you have an Atwood water heater more than 20 years old you should replace it before it pinholes and destroys the framing of your RV or trailer.

 

[LarsMac]

Maybe the takeaway here should be that if you have an Atwood water heater more than 20 years old you should replace it before it pinholes and destroys the framing of your RV or trailer.

Or, perhaps follow recommended practices of regular, semi-annual inspections to catch issues before they become so serious?

 

[JayArr]

I guess that's my failing. I did inspect around the HW heater but the leak was so small I didn't detect it. There was never any pooling of water. This must have been a slow drip. The rotted wood was all behind the paneling and below the floor linoleum so it wasn't visible until I started taking things apart. Luckily there was no mold.

I will say that the pump coming on in short bursts once an hour or so should not have been ignored. I figured it was a leaky check valve that was letting the pressure drop but I now think it was the pinhole leak slowly dripping until the pressure in the HW tank dropped below the pump threshold.

 

[LarsMac]

I guess that's my failing. I did inspect around the HW heater but the leak was so small I didn't detect it. There was never any pooling of water. This must have been a slow drip. The rotted wood was all behind the paneling and below the floor linoleum so it wasn't visible until I started taking things apart. Luckily there was no mold.

I will say that the pump coming on in short bursts once an hour or so should not have been ignored. I figured it was a leaky check valve that was letting the pressure drop but I now think it was the pinhole leak slowly dripping until the pressure in the HW tank dropped below the pump threshold.

Sorry you had to deal with that. I have had a couple of those "Hard Lessons" too.
I had a situation where the pump was doing that. Took me a couple of days to find a cracked pipe joint in line to the bathroom sink.
Fortunately, it pooled on the linoleum, and evaporated before collecting enough to get into the wood.

 

[CharlesinGA]

Atwood water heaters are manufactured and shipped with the external mounting flange folded inward so they fit in the box and the flange doesn't get damaged. Upon installation, you have to bend the flange 180 degrees to the outward position. Atwood scores the fold point and this creates a path for water to get into the structure on the sides and most importantly, on the bottom. You can seal around the edges all you want, but unless you seal the score line or use lots of butyl tape on the back side of the flange at installation, and seal the corners at the reinforcing plates, water will find its way thru these score points. It may be rainwater that runs down the side of the RV and gets under the cover and pools at the bottom, or dripping from the pressure relief valve, and of course, if you unscrew the drain plug and allow the tank to empty, it can come from that also. I have taken to using some duct tape and a cardboard canned coke carton torn to make a funnel of sorts and tape it to the heater under the drain plug. This prevents water from finding its way to that mounting flange. With my current Bigfoot trailer I still need to mask and run a bead of sealant over the score line to seal it for sure.

I encountered this with a Thor 180 Freedom Spirit that I have sitting in my shop. I bought this to use as an interim trailer while I was looking for my "keeper". Well, I ended up re-roofing it and that went well, and then I discovered extensive floor damage at the water heater. There is damage further forward from a front corner leak, but the two were basically separated. When I pulled the water heater, I found no butyl under the flange and only sealer around the edge and then I discovered the path of water intrusion. I was in the process of upgrading the trailer to a water heater with an electric element and electronic ignition when I discovered it. Now I am slowly working to repair the damaged areas and get it back together and sold.

I found my keeper a year ago just after I discovered the water damage. Its been a long year with a lot of distractions and I have to get the trailer fixed and gone. I will reinstall the original heater and keep the new one.

Click the thumbnail to expand the pic. The red arrow is pointing right at the score line on the bottom flange. If you inspect it you will find - - - - - - - all along this edge, opening water can get thru.

In the five years now I have been avidly reading forums, iRV2, RV dot net, rvform, and the Winnebago View/Navion forum, and several other smaller forums, I have NEVER heard of anyone having a leaking tank on an Atwood except at fittings or when allowed to freeze and split open. Having a Surburban water heater would be a "no buy" for me if I were looking at an RV.

Charles

 

[JayArr]

Well, I'll be darned. I never noticed that! Great catch Charles!

I think I'll take my mig welder and run a small sealing bead around the edges to keep the water out.

Thanks!

 

[Spring Creek]

Mine must be a Suburban as it came with an anode.  But I took it out.  Banking on the theory that when I pulled the anode on my home water heater over 23 years ago due the the stench, that my RV tank will be fine, since my home water heater has never leaked or had an element replaced.

Why?  Soft water, I think.

That and I hope to heck to have a different motor home in a few years  8)

BTW, not an ounce of hard water has run thru my RV.

 

[JayArr]

To each his own.

Soft or hard water (PH levels) have very little to do with galvanic corrosion. It's not acidity or baseness that causes this problem. In fact if you have a system that uses any kind of salt to soften the water that makes it worse because you are strengthening the electrolyte.

Corrosion occurs when dissimilar metals are electrically connected by an electrolyte. Think of the childhood experiment where you put a galvanized nail and a penny into a lemon and light up a small light bulb. Inside the tank you have aluminum and if you get a tiny particle of copper or zinc in the water then the water becomes the electrolyte and electrons flow from the tank to the other particle. The purpose of the anode is to release the electrons to flow to the other particle from it, instead of directly from the tank. Whichever material releases the electron corrodes.


I would think that the best defense (without an anode rod) would be a fine-particle filter to keep the minerals out to begin with. If you have nice mineral free water you probably have nothing to worry about.

 

[Spring Creek]

Generally the goal in softening water is not about changing PH. The PH level of hard and soft water is a function of what is traded during the ion exchange.  It's not a process where the goal is changing PH.

Softening removes minerals (metals per the periodic table) that tend to have a very bad effect on plumbing, among other unwanted features.  Hard water IS caustic and causes corrosion.  I understand I've traded one or more metals (calcium, magnesium, and some iron) for others (sodium), however, they tend to be LESS damaging.  And that is the very reason people soften water; hard water is hard on things (pun intended).

I know how long a water heater lasts in my area without soft water...5-8 years, max.  They either leak, or fill with minerals, or both.  Mine is 23, going on 24 years old. My dad lives a few miles away and his is 25 years old.  I'll stand by that science.