Why corrosion only after 2 months??

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Pete147

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Hi all,

In order to keep sand and sediment out of my water lines I purchased a carbon steel Lakos Sandmaster which has worked really well. It was installed in March and I already have rust forming on the surface of the unit as well as at the in and out connections.

The Sandmaster typically has condensation on the surface of it from the cold well water running through it. I spoke to an engineer at Lakos and he said that the unit is considered defective since it should not be corroding like within only a few months. His conclusion is that likely there is electrolysis occurring due to two unlike metals touching in combination with the water, causing a current between them. Is it because of the fitting where the bottom pressure gauge is attached to is a different metal than the carbon steel Sandmaster causing the electrolysis and hence the corrosion? Same with the fitting at the top of the unit? Are those brass? I didn't purchase the parts.

I have a replacement Sandmaster coming in the mail however I want to make sure when I install the replacement that the corrosion does not occur again.

Should I use a a dielectric union? I know there is a lot of debate regarding these. Please let me know your thoughts. I've included a picture. I wish I had purchased the stainless steel model, unfortunately it's more expensive.

Rusty Lakos Sandmaster.jpg
 

Jadnashua

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Looks like brass and/or bronze, which should both work together okay. The PEX isn't a conductor, so that leaves out the pipes helping to create a circuit. Looks like there might be a steel or galvanized nipple between the tank and the coupler, but if the tank is already steel, that shouldn't be an issue. Now, if it is aluminum, that might, but then, it wouldn't rust, either!
 

Pete147

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Looks like brass and/or bronze, which should both work together okay. The PEX isn't a conductor, so that leaves out the pipes helping to create a circuit. Looks like there might be a steel or galvanized nipple between the tank and the coupler, but if the tank is already steel, that shouldn't be an issue. Now, if it is aluminum, that might, but then, it wouldn't rust, either!

Thanks for your input. This is why I'm scratching my head since it's not obvious what's causing the electrolysis and corrosion.
 

Pete147

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Use sch 80 PVC fittings between the Lakos and the Pex fittings.

Craigpump - so do you think it is because of two unlike metals touching which is causing the issue? So in my case brass or bronze coupling touching the steel but I thought brass or bronze would be a safe bet in this scenario. So would the sch 80 PVC fitting stop the corrosion in your opinion?
 

Craigpump

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It's hard to say exactly why the paint is failing, could be thin paint, moisture, dis-similar metals or a combination of all three. If you put sch 80 or even better sch 120 couplings on you're eliminating one possibility.
 
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