Ivan Vegvary wrote:
....
Almost all 75 feet is underground, ergo, I cannot add boxes. ...

Outside the already suggested obvious, then, you have one of two
choices--do the fully-right-code-compliant way or bite the bullet and
make the splice (on the assumption by the time there's a problem it
won't be yours to solve, anyway ).

If you do choose the splice route, just be sure it's made to handle the
underground conditions to be expected and sturdy enough mechanically to
handle the pull.

I had to repair a buried (no conduit) line to the well (wouldn't you
know that in an open area of a couple acres after eyeballing the run
from the pumphouse to the well I'd manage to set a post directly on the
run. If I'd been _trying_ to find it, otoh, I'd been all around.. ).
It's been almost 10 years so far w/ no problems so it can be done
physically; it's still not going to be code-compliant if that were to be
an issue (needing permits, etc., ...).

All in all, it would seem the extra investment in the wire is moderately
cheap given all else that must be going into the project (one assumes
there's something going on the end of the run... ).

Perhaps, even, one could get something back from the other wire via
Craig's list or similar to defray a portion of the outlay if $$ really
are _that_ tight...

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