During the cold snap we've been having this past week, the front koi pond decided to freeze. That has never happened before, as the combination of the pump running and the floating heater has always kept it going just fine. But during our multi-day sub-zero spell, the pipe from the pump to the waterfall froze, blocking water circulation. Then, we got a nice layer of ice across most of the pond except right around the heater.
Today it finally warmed up (much of the day over 40), so I set about trying to figure out how to get the pond running again. First thing I did was inspect the pump too see WTF.
Well, the old pump inlet was quite clogged with leaves. Plus a 3" crayfish (who perished as a result, sadly). So, I'm guessing that the flow of water was pretty severely restricted, and this was enough to allow a pipe to freeze. I may need to upgrade the pumps to what they call "sewage pumps". Those are designed to pump water that has crap in it, which they just grind up as it passes through. The pumps I have now are water pumps, and they sieve out any foreign matter in the water and thus clog with leaves all the damn time. I don't know how the leaves get in there - the box is covered and there is both a skimmer net and a 1" thick nylon mesh filter that everything has to pass through to get to the pump, yet the pumps clogs a lot.
I got to use my early-Christmas present from moother-in-law insulated waterproof gloves to screw around with the pump. My fingers stayed nice and dry and warm. I can put my hand in boiling water for up to 20 seconds and handle dry ice with these gloves, too. I'll let you know if that comes up.
Restoring the flow on the pump, though, didn't restore flow to the waterfall. Something was definitely frozen downstream. So I dumped a 5-gallon bucket of hot water into the waterfall box. This softened up the filter screens in there enough so that I could remove them, but the water stayed in the box. That box is higher than the pump, so normally if the pump is off, water will flow out of the box back through the pump. Nothing doing.
Next, I got another bucket of hot water and poured it over the ultraviolet sterilizer. It's about a 2-foot long PVC tube with a UV lightbulb down the center. I figured it might freeze given it's not really buried (cuz you have to change the bulb every year), but just has some rocks piled up on it. Still, the water stayed in the waterfall box.
I went inside to refill the 5ga bucket with hot water. When I returned, I noticed that the water level in the waterfall box was suspiciously lower than it had been earlier. Could it be? It couldn't be this easy. Could it?
I poured the hot water into the waterfall box, and I watched the level slowly go down. Sure enough, I could see the water flowing back out of the pump box at the other end of the pond. When it had emptied itself out, I turned on the pump. Voila! Waterfall.