That time a knob and tube splice nearly burned down a garage in St. Louis

I was doing a service call at this old house in St. Louis last Tuesday, and the homeowner said the garage lights kept flickering. I popped open the junction box and found a knob and tube wire spliced into some old romex with just electrical tape and no box cover. The insulation was crumbling off the hot wire and it was touching the bare ground. I shut the power off immediately and told the guy we had to rip it all out right then. He was not happy about the emergency cost, but I showed him the scorch marks on the wood and he changed his tune quick. Has anyone else run into sketchy old splices that were just waiting to fail?

3 comments

3 Comments

webb.hannah6d ago

and the scary part is that old knob and tube wasn't even grounded properly in the first place, so that "ground" wire was just a loose path to something. if the breaker hadn't tripped, you could've had a fire before the homeowner even noticed the flickering lights.

robin8966d agoMost Upvoted

Oh absolutely. My buddy bought a house with knob and tube still live in the attic, and the previous owner had just capped loose wires with electrical tape. One of those "grounds" was just wrapped around a rusty water pipe that didn't even connect to anything. We found it when his bathroom light started flickering like crazy during a rainstorm. Turned out water had dripped onto a junction box that wasn't even sealed, and the whole thing was just arcing inside the wall cavity. He had an electrician out the next day and they had to rip out half the ceiling to replace the runs. That stuff is basically a fire waiting to happen, and half the time the breaker doesn't even trip because the circuit is so old and finicky.

cora8136d ago

Yeah, you're mostly right about old knob and tube being a fire hazard, but actually the "ground" wire you described was probably never a ground at all in the original setup. Knob and tube systems didn't have ground wires, they just ran hot and neutral. What your buddy's previous owner did with that rusty pipe was a bootleg ground, which is dangerous but it was never part of the original design. @robin896, your buddy's lucky they found it before anything worse happened, because old rubber insulation on those wires gets brittle and cracks, and if moisture gets in there it can arc between hot and neutral without ever tripping the breaker since there's no proper ground path. My grandpa's house still had some in the basement and we replaced it all after finding a spot where the wire was just bare copper against a floor joist from an old rodent chew.