I just replaced my 6 yr old water heater which sprung a leak at the top weld (a topic for a different post). The water heater has side ports and is used to source indirect closed loop heating for a radiant slab. The potable water for the house is CPVC, so no dielectric concerns there. However the piping to the heat exchanger is copper to support the circulating pump. The heater has been in use for 6 years, but the heat system was added only 3 years ago. The heat system is connected to the tank through a standard (non-dielectric) galvanized nipple at the tank to a dielectric union to copper. After just three years the galvanized nipple is 50% blocked.

I've done a bunch of reading, and can't quite nail down an answer.
> Should I be using a plastic lined nipple to keep the waterway open?
> Would a brass nipple be better, or would that just cause a problem at the tank connection?

Thanks

I'd use brass.

Brass for me too.

a galvanized steel nipple in a domestic water system is going to rust no matter what it is connected to.

If the leak was at a top connection and the copper is connected to the side, there should be no correlation between the two.

The leak was most likely a flaw in the tank weld. I know it's not related to the copper connection. But since it's all taken apart and installing a brand new tank, I thought I would use something that will stay open longer than a few years. Sounds like brass is the way to go but wasn't sure about attaching a brass nipple directly to the steel tank. It's probably a better option though since it's hard to find dielectric nipples long enough to reach the port. I think I needed a 5" nipple to have enough to get a wrench on to tighten...which is why the regular galvanized ran to the dielectric Union. A 6" brass nipple shouldn't be hard to find.