Brass all thread

Perhaps a bronze, called "naval brass". That tends to be an alloy which can handle chlorine corrosion, sicne the sea has lots of NaCl. :-)

Enjoy, DoN.

Chlorine as chloride (what's in seawater) is not chlorine as hypochlorous acid (what's in a swimming pool).

Chlorinated swimming pool water will (slowly) dissolve even gold.

I'll go out on a limb here. My SWAG is that because it is inside a pool filter, that it was made with chlorine corrosion in mind. Ergo, a marine brass, or some particular type of metal that still looks good today after probably twenty years of use.

Even if I have to reweld the ends on every few years, that's better. The problem is that when you lift the whole assembly out, it is caked with DE, and if one of those cuts loose, about fifty plastic parts go flying, some with self destructive results. After sitting in there a year unmoved, it is a little tempermental. Had to replace three panels on the first cleanup. Luckily they still make the parts, but it would have been a lot simpler if it had just held, and there was no damaged parts.

Just a guess.