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Replacing Furnace Drain Valve

Posted by UltimateAtrophy (My Page) on
Sat, Mar 16, 13 at 18:28

I have 4 "lines" from my oil furnace in and one of the lines has a severely corroded black iron T pipe fitting that connects to a drain valve. 2 of the other lines show no corrosion, and 1 line shows minimal corrosion. The fourth line is really corroded and drips water. Copper pipes connect to the iron t fitting. I have baseboard heat with basic copper fins.

I'd like to understand why this happend so I can properly fix the issue.

1) Why did this corrode so much? Is there some galvanic corrosion going on? See picture attached

2) If it is some sort of galvanic corrision, should I put some type of dielectric union in between the copper and iron? I've read some mixed reviews about this on the forums.

3) To replace the iron t-fitting, I am assuming I should just cut the copper pipe and replace with the iron t. Is there an optimal place to cut the pipe? See picture in link below-option1 or 2 or is there a third?

Full pictures here:

I've been a part time lurker here-but this is a great site. Thanks,

Follow-Up Postings:

RE: Replacing Furnace Drain Valve

I would first try just replacing the valve, or removing and properly cleaning and reinstalling the current one, making sure to make it a water-tight fit. If you can stop the drip, the rust should also stop.
If you end up replacing the T, I'd unsolder the copper pipe from the fitting, not cut the pipe. Be aware that any resoldering on this system can be frustrating as any stray drop of water can defeat a good joint.

RE: Replacing Furnace Drain Valve

I was going to try to replace the valve first, but be prepared for a much more extensive overhaul if that doesn't work out. Keep it simple right?

Thanks for the resoldering tip. I though you shouldn't resolder a joint-but I just readup that you can. Thanks,

RE: Replacing Furnace Drain Valve

Hydronic systems get some relief on galvanic corrosion from keeping the same water for long periods of time.

The ion load that can allow corrosion gradually decreases (by causing corrosion) until there are not enough ions in the water to drive much corrosion.

If you have to routinely add fresh water into the system, it brings in a new load of dissolved oxygen and other ions that start another round of corrosion.

De-ionized water is actually an electrical insulator.

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