Sink Repair

I have become a plumber.  My sink stopper won't go up anymore.  It is stuck in the down position so the sink fills up with water.  The problem is this part has a pin that raises and lowers the stopper broke off.  

I have fixed this for my dad a long time ago.  This is what the part looks like.  I need to replace this ball thing.  (I have old lady hands....like my mother...)

Problem is I went to home depot to get the part and bought it.  The ball thing was too small so it leaked.  It was the only one they had. Ordered another on Amazon with different sizes and it worked.  Problem is it still leaked but from that black thing.  So I used the original metal Nut and it still was leaking.  Chris at work told me that you have to screw the nut on tight.  So, i climbed under the sink, took the picture and screwed that nut.  What do you know, it works and doesn't leak.  

I also need to fix my toilet.  The part with the ball coming off  is leaking.  My friend Sandra changed hers out and said it took about 20 minutes. I have the part but haven't done it yet. I just don't want to do it.  But I have to before it gets worse.