It seems to me to be a problem with the float, but it's not making a whole lot of sense to me, and I'd like feedback before I invest money into a new float.

I don't know what's standard for these pumps, but one thing I noticed is that the pump is not able to drain all the effluent in the sand filter. After the level gets a bit below the height of the pump, it stops draining it. Is this normal? Is the pump already going bad? It's 5 years old.

Anyway, I adjusted the float that controls the pump so it should turn off with a higher effluent level, and it seemed to work at first, but somehow the pump starts going again when it has power after a long time even though the effluent level never raises enough to even move the float, and then the pump never stops going. Does this mean the float is bad? I can't think what else it would mean, but the float works properly when I raise and lower it myself with a long poll.

Is there something I'm missing to look into here? I'd love to hear from someone that knows what they're talking about. Thank you.