Are fish pond UV light ballasts typically somehow connected to the water pump?

They should be two totally unrelated things. Question about your pump. Is it an external or internal pump? If its external it could have been ruined in the same way the ballast was.

They are not connected (except possibly indirectly through a circuit breaker).

I think it is internal….there is a portion that stays submerged and sucks water in. I think this water goes into the UV unit and “clean” water is pumped out into a water feature.

Thanks @syz

Good call on the circuit breaker. So I reset the main one as well as the sub- (breaker?) that directly controls the fish pond pump/filter and that fixed the problem…for about 15 minutes. Then the pump was off again. I reset the breakers again and now when I flip the pump switch on it just trips immediately. Glad there is nothing wrong with the pump/filter itself. But any ideas why this happens? I think the only thing this subbreaker is connected to is the pond pump so there are no other loads. I have no idea how the pump could overload the breaker and from the portion of the wires that I can see, none of them are touching or anything…

Did it work correctly before the rain? If so, you know it was installed and wired correctly to begin with, right?

Yes it worked fine before rain. It was installed and wired correctly to begin with.

You should have your wiring checked for a short circuit. Do not continue to throw or force the breakers ON as it may surge and kill your fishes. The breakers are doing the job of tripping when there’s a short in the circuit.

I’m an industrial electrician but I rarely mess with house wiring, except for people I know very good so perhaps I can help. I’m not great at picturing things in my head so you may have to help me here. First of all I’m not sure how your pump or light is hooked up and I’m not familiar with this type of setup since nobody I know has an outdoor fish pond with a UV light. How is your pump motor wired? Is it plugged into an outdoor GFCI outlet or is it hardwired to the breaker panel in your house?

From what you’re describing though it is probally a safe bet you got water inside of the windings for your pump motor somehow, perhaps inside of terminal connection box (peckerhead) of your pump. Disconnect the power to your pump and try to take the motor apart to look for water (if possible since I don’t know what type of motor you have).

I’ve seen this happen to many larger motors in my line of work so I would not recommend energizing the pump anymore until you’re sure the copper windings inside the motor are dry or not submerged in leftover water or you will damage the entire pmp assembly. Hope this helps.