I have a Sequence 4200SEQ12. Been in service for just over a year.
From day one the plan was to have a backup pump to keep in stock just
in case anything went wrong. Lately, I've noticed my stream starting to
slow down to almost a trickle. Not even enough pressure and flow to
operate the second barrel filter let alone the first. So I ordered the
backup pump. Today, the stream would only give a drip or two. I pulled
the cover off of the pump box and it sounds like it is running fine.
No cavitation sounds. Motor doesn't sound like it is laboring. So I
pull off the strainer to see if it is clogged somewhere where I can't
see. Nope, no clogs. I reach my fingers into the pump inlet pipe.
Nope, feels nice and clear. Okay, so I get a fish tape ( makeshift
snake.) I slowly push it into the inlet, it is only about 2' to the
impeller. Bzzzzzz. I bump into the impeller. So I back it out and
slowly push in again. I can feel the center of the impeller spinning.
I push a little further and buzz it again. Yup, definitely spinning.
So I pull the fish tape out.

I scratch my head. Then I notice water starting to draw just like the
day I first hooked it up?!? What was that all about?? Well, water is
flowing again, both barrels filtering, waterfall splashing away. I
wonder if the impeller is somewhat loose? Well, in two days the backup
pump should arrive. I'll install it and pull the old one to inspect,
refurbish and put up on the shelf. Any thoughts??

BTW, I'm just about to call this project officially done! Just a few
more details. http://www.bunchobikes.com/pond9.htm