Buderus indirect pipe corrosion threads

NateP

On a Buderus indirect water heater, I am getting significant corrosion on the hot water outlet pipe. The pipe appears to be black steel and connected to it is a 1" brass T which houses the pressure relief valve and the main outlet for hot water to the house. I believe brass doesn't corrode steel quickly, but apparently it is here. Only been in service for 5 years. The magnesium anode in the tank is still in halfway decent shape

A small drip started between the brass T and the outlet pipe. I took it apart and found about one half of the end of the black pipe is corroded away and significant amounts of built up rust in the pipe.

The threads are shot and I would like to try and avoid replacing the entire expensive tank. Is there some type of high temperature compression fitting or any other type of solution that can be used here?

SWEI

Is this an SST or a WST? Has anyone checked the anode rods?

NateP

Model ST300/2
Anode rod passed multimeter test with 17mA (right in between reccomended range of 0.3 - 30mA). Visually inspecting the rod shows it has been worn some but still about 1" thick. Buderus manual reccomends changing after down to 1/2"-3/4"

SWEI

Sounds like the tank spud and not a separate nipple. If that's the case, you might be able to squeeze a bit more life out of it by cutting it off and installing a MegaPress male adapter. The cut off edge will become the focus of future corrosion.

Quite likely a water quality issue -- think chloride levels, low pH, or a water softener.

NateP

No water softener has been used. Chloride level is 80 ppm and pH is 7.2. Is that a high Chloride level? I wouldn't have thought so

SWEI

80 PPM is an order of magnitude higher than anything in our neck of the woods. For reference, 100 PPM is generally regarded as the safe limit for 304 and 304L stainless.

NateP

Thanks so much for your help.
I didn't realize that 80ppm for chloride was on the high side. I guess that plus the brass transition T fitting is aiding the corrosion.

As some of the threads on the pipe are still there, would it work to try and thread a 1" black iron extension pipe coupling between the hot water outlet and the brass T and see if I can get the leak to stop there? I'm thinking if there is future corrosion, maybe it would happen between the new coupling and the brass T.

SWEI

I don't know if that would have the intended effect.

If the threads are saveable, I'd probably clean the spud thoroughly and install a 304 stainless coupling (cheaper than brass, and also closer to steel on the galvanic series than 316 SS), and use an anaerobic threadlocker (instead of tape or dope) on the tank side. Give it 12-24 hours before you apply full pressure.

Rich_49

PermaBond LH050

Mark Eatherton

The problem with older Buderi horizontal tanks was that the mild steel tank was glass lined. The nipple was also mild steel. While the nipple did receive some glass lining internally, the very end was exposed mild steel. This starts the process of corrosion on the nipple end and it ends up consuming the nipple and eventually causing leaks.

Yellow brass is actually considered an acceptable method of making a dissimilar metal connection.

Propoxy and start saving for a new tank. I hope they have changed their designs by now. I haven't installed one in a LONG time...

ME

NateP

So if the corrosion is slowly eating away at the end of the nipple, is there some sort of compound or sealant I can put on the end of the exposed nipple that will seal it and prevent future corrosion?

Mark Eatherton

Epoxy? You'd want to make certain that what ever you use is not toxic to humans. I'm thinking once cured, it's OK, but best to check.

ME

rmccomiskie

Yes. I know this is an old thread. I'd like to add to it. My Buderus LT160/1 indirect water heater has failed in exactly the same way as the OP. In fact, this is the second time. My original LT160 was installed in 2014. When it failed in 2020, just within the original 6 year warranty, Buderus sent me a new LT160. It was installed in 2020. Now, here it is 2023, three years later and the hot water spud started leaking. The service company that installed it said that the tank can't be saved. Buderus has declined my warranty claim because I am outside the original 6 year warranty period. Did you know that a replacement is only covered until the end of the original warranty? Buderus also threw in that if the water quality is not within their specs then the installer should have used dielectric unions to connect to the tank. What is a dielectric union? So I am in the spot as the OP. My tank has failed and I won't buy another Buderus. I have a little time to work on this because the service tech was able to cobble together the fittings so we have hot water. But, he said it is only temporary and may, or may not, hold. So my search is on for a reliable tank. I'm also going get an analysis of the water supply to see if there's an issue. Cheers. Bob.

kcopp

Yes the warranty policy is pretty much that way for most all WH mfg.
I just ran into a similar issue w/ an electric...
Well water? Municipal water?
May want to also look to see if there is any stray current in the piping....that will kill a WH in no time.

GGross

rmccomiskie said:

Yes. I know this is an old thread. I'd like to add to it. My Buderus LT160/1 indirect water heater has failed in exactly the same way as the OP. In fact, this is the second time. My original LT160 was installed in 2014. When it failed in 2020, just within the original 6 year warranty, Buderus sent me a new LT160. It was installed in 2020. Now, here it is 2023, three years later and the hot water spud started leaking. The service company that installed it said that the tank can't be saved. Buderus has declined my warranty claim because I am outside the original 6 year warranty period. Did you know that a replacement is only covered until the end of the original warranty? Buderus also threw in that if the water quality is not within their specs then the installer should have used dielectric unions to connect to the tank. What is a dielectric union? So I am in the spot as the OP. My tank has failed and I won't buy another Buderus. I have a little time to work on this because the service tech was able to cobble together the fittings so we have hot water. But, he said it is only temporary and may, or may not, hold. So my search is on for a reliable tank. I'm also going get an analysis of the water supply to see if there's an issue. Cheers. Bob.

Change your search to include a different installer as well. You just don't see these fail that quickly except from site conditions. There are many indirect water heaters that have lifetime warranty for the original owner as well.