question on galvanic action

[MW]

I moved to a house that is over a century old and noticed most of the upper floor water lines to be newer copper but the lower main lines galvanized steel

Won't this lead to rapid deterioration of the lower water lines?

I would also like to know general guidelines for avoiding galvanic action on piping and so forth I need to have a water heater installed andwas told to use fittings which use a mix of different metals in it's construction... Why is this, and how does this negate galvanic action by merely being a mixed metal fitting?

Thanks Joe

[trader4]

I moved to a house that is over a century old and noticed most of the upper floor water lines to be newer copper but the lower main lines galvanized steel

Won't this lead to rapid deterioration of the lower water lines?

"I would also like to know general guidelines for avoiding galvanic action on piping and so forth I need to have a water heater installed andwas told to use fittings which use a mix of different metals in it's construction... Why is this, and how does this negate galvanic action by merely being a

mixed metal fitting? "

This is a long and complex subject. If you do a google search for galvanic and water heater you should find lots of threads. The idea of the different metal couplings is that the two different metals are seperated by an insulator, making it a dielectirc union. That way, there is no current path between the different metals. However, there is still a path for current through the water itself. And then there is the issue of ground path bonding. Normally, all metal water pipes are tied together within a house and tied to ground. Inserting a dielectric coupling breaks that path. If you jumper over it, then you defeat the purpose of the dielectric union.

I have heard mixed reports in practice as to whether using these unions on a water heater makes things better or worse. And I think the answer depends on a lot of things. Most water heaters don't have them and the plumbing connections seem to last just fine. Mine doesn't. I replaced the original gas water heater at about 12 yrs, which is pretty normal. No evidence of corrosion at the fittings.

[Colbyt]

This is a lay person response based on 30 years of personal experiences.

The problem is greatly overstated.

Most problems will occur at the point of joining the different metals.

Purity is best but not always practical. Keep the transition in a visible location.

Your water heater will die in about 10 years or 1 year after the warranty no matter what you do or don't do.

Colbyt

[Porky]

Just a thought. Galvanic action is a serious problem for boats in salt water, and maybe more of a problem if there is a high mineral content in your water. Consider converting to plasitc pipes for DIY plumbing. Check your electrical ground, you may need to install a new ground rod or plate.

JohnK

[Joseph Meehan]

As noted the problem is complex. Part of the formula is the water (acidity salt content etc.) electrical grounding and others. The short answer is if the plumber did the job right, it is not a problem. The problem comes up when the plumber takes shortcuts or the home owner does not know better. It seems you do.

[Jose]

Just an aside...

I have installed a ground rod and wire to solve the problem of grounding via waterpipes but I just read in fine homebuilding mag of a person who stated that galvanic action was so important you should not use galvanized hangers of any type with copper spouts (I have copper spouts) ..and brought up the statement of a 'nomenclature or hierarchy of metals which should be used in conjunction with each other to avoid galvanic action and it set me to thinking on the bit of galvanized main line I have and the connections to my copper lines as well

Thanks for the info and link.. I will hit the link provided

Joe

PS: The union for the new direct vent water heater I intend to install doesnt have dielectric properties but merely a transition of metals within itself --strange I thought as that would only exacerbate the problem I would think unless the particular metal plating was of a particular order of metals that was related to that "hierarchy" I read of

- confused but willing to learn

[Bob]

I've been in my house for 16 years. I guessed the water heater was many years old when I moved in. I just replaced it.

Bob

[Bob]

I just installed a new water heater - it came with dielectric nipples.

I was told recently that brass connections between copper and galvenized steel will work as well as isolating junctions. I also was told that bonding the copper to the iron with a wire when connected with isolating junctions does not cause corrosion. Opinions?

Bob

[trader4]

"I also was told that bonding the copper to the iron with a wire when connected with isolating junctions does not cause corrosion. Opinions? "

I don't see how that's possible. The classic experiment showing galvanic action is to take two different metals, place them in an electolyte, and measure the voltage between them. When connected by a wire, the less noble metal will corrode. This is them method used to protect boats. All the underwater metal is bonded together and zinc is used as the sacrificial anode. At best, I would think using a bonding wire across the dielectric unions would move the point of corrosion and perhaps distribute it over a different area.