On 02/01/2017 06:47 AM, Unquestionably Confused wrote:
Other than for underground wiring connections, which are about like a
skinny cigar tube and have clamping screws and silicone gel to
weatherproof them, I don't recall seeing butt connectors rated for
household voltages. All that I have or have seen were for low voltage use.

You have seen very many then. The common vinyl insulated butt splices
are 600V rated. Some of the nylon type are 300V, some 600V.
non-insulated butt splices are just a copper tube. Do your own insulating.

Or the OP could use a Western Union splice and shrink tubing. That would
hold up better if you drag the vacuum around by the cord.