# Stainless steel and domestic water lines.



## NewisCool

I've been told stainless steel reacts with copper. But not with brass.

Also been told that stainless steel reacts with water period. Corrodes away.


Different folks different thoughts. The question came up because we're doing a job on a DHW system. Mostly copper with a few stainless steel isolation valves tied to pressure gauges which are also stainless.

One is threaded into copper. One is threaded into brass. bypass between them with a SS pressure gauge on it. 

Same thing in several locations. 

Initially told to take SS off copper only. Done.
Later had to go take SS off brass as-well. Done.
I brought up the SS gauges and they're going to get some brass ones I guess.

As an apprentice I don't have much input into what's going on. 
Personally though I would've preferred to have gone in scoped out ALL the parts that needed to be replaced. And known the reason! It's hard to be satisfied with my work when I only have vague ideas as to why it's being done. 

Your thoughts?


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## Olemissplumber

Stainless steel comes in many grades some are more corrosion resistant than others. 316L is considered good quality.


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## NewisCool

The quality of the stainless wasn't in question in this case  

more basically.

I am under the understanding that stainless steel mixed with brass is not an issue. Stainless steel mixed with copper is not an issue. Stainless steel carrying drinking water is not an issue. That's what i thought.

Being told otherwise. And i'm not sure.  I'm probably wrong but would like someone to straighten me out.


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## Olemissplumber

Again it depends on the quality of the stainless steel. Different qualities are a different make up and react differently with other materials.


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## Chadillac80

So what about the ss w/h flexes? Are those "good quality" :blink:


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## NewisCool

I think it's pretty safe to assume that the gauges are either 304 - 316

SS and water being a concern. I see no reason for this to be true. Can someone confirm this for me?


SS and copper makes more sense to me. galvanic reaction. But I haven't been able to find a clear reference to this.

SS and brass same as above.

Does anyone know of any reason why stainless steel 304-316 fittings can not or should not be used on water lines?


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## Olemissplumber

The environment in which the materials are installed have a great influence on possible corrosive reactions. I have never witnessed a negative reaction of any significance between brass,copper and a good quality of stainless steel.
That being said I removed 6 galvanized steel nipples that were used for fixture stub-outs threaded into copper drop eared ells that had been in service for 60 years. The inside of the nipples had almost closed up completely.

There are a lot of variables that contribute to the rate of corrosion. 

In most cases I would feel comfortable mixing brass,copper or stainless in any combination for potable drinking water if those materials are commonly used in the area. In other words mixing wouldn't cause accelerated corrosion that wouldn't occur anyway.


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## NewisCool

Right. Everything will corrode over time. 

But I was pretty sure that there wasn't a issue with the stainless in the first place.


Guess i was right :blink:


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## justme

You can connect copper and brass to stainless but don't ever connect galvanized to stainless in a potable water system it will corrode and close up in no time.The newer stainless steel water heaters coming out specifically state that if you use a dielectric union the factory warranty is voided.


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## plumbing ninja

Most SS in piping is 304, 304L 316 or 316L . The L grades are better to weld with. The 304 is not as corrosive resistant as 316 due to the nickel content. Copper to SS best use a dielectric union or flange to make the join. SS pressure gauges normally will tap into a brass valve or thread fitting not directly into the copper!
If you pass a magnet over 300 grade ss it will stick. 304 slightly maybe and 316 should not stick at all! This is how you can tell if you've got a genuine 316 bench top or had a con job pulled on you


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## NewisCool

Yes I think I understand much better now. Thank you all! :thumbsup:

Also I found this: http://www.corrosionist.com/Galvanic_Corrosion.htm

It seems to be discussing the situation from a architectural point of view.

But helped me wrap my head around the details of Galvanic Corrosion


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## NewisCool

plumbing ninja said:


> Most SS in piping is 304, 304L 316 or 316L . The L grades are better to weld with. The 304 is not as corrosive resistant as 316 due to the nickel content. Copper to SS best use a dielectric union or flange to make the join. SS pressure gauges normally will tap into a brass valve or thread fitting not directly into the copper!
> If you pass a magnet over 300 grade ss it will stick. 304 slightly maybe and 316 should not stick at all! This is how you can tell if you've got a genuine 316 bench top or had a con job pulled on you


Hmm.. It is possible that the Gauges were of low quality. 
I'll have to stick a magnet to them next chance I get. Found this trick useful to know thanks  

So would it be a good rule of thumb to go SS-Brass-Copper instead of straight 
SS to copper?

http://www.corrosion-doctors.org/Definitions/galvanic-series.htm


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## MollyW

SS should most definitely NOT be corroded by water.... I don't think regular carbon steel should even react with water.


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## CT-18

When I was in the field doing Ford field here in Michigan we ran the water mains in 12" thin wall stainless grooved. We used isolators when we branched off to pro press copper.


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## breplum

Mixing metals always invokes electrolysis which causes galvanic corrosion . The differentials from s.s. To brass depends upon the electrolyte (Probably water in your case?) If that’s the case then there will be galvanic corrosion but it will only be moderate at most. If you don’t want mild to Moderate corrosion then avoid stainless steel intermixing.


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