I always use A blood knot but I make sure it is down well beyond casting range. When I spool new line I strip off about half a spool, use that for leader material and tie a blood knot to add new line. Blood knots are strong if tied right. Take two line ends. Make a loop in one end and wrap it's end up about eight wraps then pass it back through the loop. Do not cinch it yet. Take the remaining line end, pass it through the wrapped loop, make it's own loop and it's own eight wraps passing it's end back through it's loop. Now pull both lines carefully until the knots slip down and cinch. Snip the remaining ends. Does that make any sense?