Is my water heater installed incorrectly?

We bought our current house about 5 years ago. The previous owner had a new gas water heater installed just prior to selling us the house. I just noticed that there is a lot of scale and what appears to be corrosion around the area where the supply lines connect to the water heater.

I took a close look at the set-up, and from a galvanic corrosion standpoint, I think it may be wrong. The plumbing in the house is all copper. In the wall behind the water heater are 3/4" copper supply lines with sweated-on brass elbows with mounting lugs secured to blocking. A 3" to 4" iron nipple is threaded into each of the elbows and two more nipples into the two ports on top of the water heater. A copper flex line then connects the nipples from the water heater to the nipples coming out of the wall. All of the scale and corrosion seems to be at the water heater end, not at the wall. Is this a correct set-up? If not, what is the correct method of connection? Use dielectric unions?

Thanks,
Steve

The nipples at the wall elbow should not be steel ( not even galvanized). At the water heater, dielectric nipples could be used ( galv. nipple with a plastic lining ). Regular black or galv. nipples should not be used.

Here's the order of fittings to connect a heater, assuming copper supply line and household plumbing. A tee in the water supply line with one side going to supply the house with cold water. The other side of the tee should go into a shut off valve. I prefer a full flow ball valve. The copper flex line comes next. On the out flow end of the flex, there should be a dielectric nipple, and the other end of the nipple goes into the input on the tank. Going from the tank, use another dielectric nipple, flex pipe, valve, hot water supply line to the house. (The second valve is probably not really necessary, but I use one anyway) Those two nipples should have been included with the tank, but you can purchase them separately.

Thanks guys. I forgot to mention that there is a brass gate valve on the cold water side threaded onto the nipple at the wall, with another short nipple threaded into the other side of the valve and connected to the copper flex.

Jimbo,
What should the steel nipples that are threaded into the brass elbows in the wall be replaced with? Brass nipples? Or can I use the dielectric nipples here also? I coud also sweat a couple of 3/4" male thread adapters to each end of a short piece of copper pipe and use that in place of a nipple. Last resort would be to remove the sheet rock and stubb out for the water heater.

-Steve

heater

Use brass nipples. Dielectric nipples are better in concept than they are in practice. They are notorious for failing and when they do, they are a major source of rusting.

Thanks HJ.

So I should use brass nipples at the wall and dielectric nipples at the inlet/outlet of the tank?

-Steve