I built PVC housing for my Eheim Jager 125W and plumbed it into my FX5 outflow hose about a month ago. I used a 3/4" uniseal to insert the heater into 1 1/4" PVC pipe. It all worked perfectly until Monday night... Fortunately, I was sitting right next to my aquarium watching TV when it started leaking, because two seconds after I heard it leaking, the uniseal popped out entirely and I had 900gph shooting out from behind my tank.
I sprung into action, turned off my surge protector and closed the valves on my filter so it wouldn't siphon all the water out, checked to make sure no electrical outlets were wet, and started cleaning up water. In the blink of an eye I had about 6 gallons of water on my floor... Fortunately, it was about 8:30 when I finished sucking up water and the home depot was still open, so I went and got a PVC cap to make a quick fix. Right now the heater is just in my tank until I feel like taking the damn thing apart and fixing it.
My guess is that the fatal flaw in my design was inserting the uniseal directly into the PVC pipe, instead of using a cap and drilling a 1 1/4" hole in it. When I rebuild, I will probably use 1 1/2" PVC and cut the hole in the cap. The uniseal instructions provide a maximum wall thickness, so I'm almost 100% sure that's the issue.
Here's a professional rendering of what I'm talkin' bout.
PSA: Drip loops, GFCI outlets, and surge protectors (especially because you can turn everything off with one switch). HAVE A PLAN, think about what you would do in a disaster situation.
...I really don't want to think about how epic this disaster would have been if this happened while I was at work. I would have had 40 gallons of water sitting on my floor for hours, an empty filter and power head running dry, probably a busted heater (hopefully not a fire) from running dry, dead fish, and a properly freaked out turtle.
I plan on getting a water sensor with wifi connectivity to send me alerts on my phone. I can't live with this paranoia!