I built a heater into my DIY CO2 reactor top. The reactor itself is made from scrap 4" PVC about 18" long I had left over from another job. The large diameter reduces the water flow inside and increases the dwell time at the heater. Plus its what I had
The bottom of the reactor is a 4" PVC cap the top is a 4" PVC cleanout that has a threaded cap for internal access. Everything was glued with PVC solvent cement. All glued joints were cleaned with PVC joint primer.
I drilled a hole in the center of the cleanout cap, threaded it and glued in the rubber compresion fitting that holds the glass heater. I sealed the glass heater into the compresion fitting with some silicone (not grease) sealant as extra insurance, before I carefully tightened it.
The inlet and outlet are electrical PVC 5/8 hose barbs (used for flexable plastic electrical conduit).
The inlet is glued into a drilled and threaded hole in the side of the cleanout fitting where it is thickest. The outlet is in the side of the cap in the bottom.
The CO2 inlet is a small lawn 1/8" sprinkler head and extention siliconed into a smaller rubber compression fitting. The compresion fitting is glued into a drilled and tapped hole in the cleanout 90 degrees from the inlet.
I filled the lower 1/2 of the reactor with 1" sections of 3/4 PVC electrical conduit left over from another job. (I figured the might help mix everything. It was free and cut up easily on my chop saw.) I picked everything I didn't already have on one trip to Home Depot.
I let it all dry for a week outside and flushed it with water with a garden hose for a 1/2 hour before I hooked it up.
It works great, no leaks, the tank stays warm and the plants are pearling. I unfortunatly don't have any pictures since its impossible to photograph under my show tank. I'll will be making another soon and will take some and post some then.