I get where you’re coming from—old threads can be a real wildcard, and sometimes you just don’t want to gamble with a single layer of tape. I’ve seen plenty of “quick fixes” turn into headaches down the line, especially in buildings where the pipes have been around longer than most of us. Pipe dope definitely gives that extra peace of mind, and doubling up isn’t as uncommon as some folks might think.
That said, I’ve noticed that combining tape and dope can actually help fill out those worn threads, but it’s worth being careful not to overdo it. Too much buildup can make it tough to get a good seal or even risk cracking a fitting if you really crank down on it. I usually go for two or three wraps of tape—making sure it’s snug and smooth—and then a thin layer of dope on top. That combo’s saved me more than once, especially on galvanized lines that look like they’ve survived a few world wars.
One thing I’d add: if you’re running into leaks even after doubling up, sometimes it’s worth chasing the threads with a die or wire brush first. Gets rid of the gunk and corrosion so your sealant actually has something to grip onto. Not always possible in tight spots, but it can make a difference.
You’re not alone in wanting that extra insurance—nobody wants to be crawling under a sink at 2am because something let go. There’s no shame in being cautious, especially when you know what’s at stake if things go sideways. Sometimes “overkill” is just another word for “sleeping through the night.”
Honestly, I think you’re spot on about not wanting to risk it with old threads. I’ve seen way too many “that’ll do” jobs come back to haunt people. A little extra care now really does save a lot of stress later. That tip about cleaning threads first is underrated—makes a huge difference, even if it’s a pain in tight spots. I’d rather take the time than deal with a midnight leak... been there, done that, never again.