Most aquarists are familiar with solvent welding (bonding) PVC fittings & pipe together. But when it comes to bonding PVC to ABS, there are a few differences that are very important.
With respect to the most recent Turbo Algae Scrubber, these differences are very important – improper solvent welding can lead to weak and leaky joints, which may require part replacement in order to remedy.
Rule #1: All Purpose Cement is idealOne that lists both ABS and PVC on the label. In reality, most any cement is going to be fine, like Oatey Medium Clear. Just make sure to follow Rule #2.
I used to recommend trying to use Transition Cement, but this is not really necessary. What is more important is not applying primer OR cement/solvent to the ABS part – ONLY the PVC side. This is covered in Rule #2
Likely, regular PVC cement will work also, but I have not thoroughly tested this. People regularly bond PVC pipe into ABS bulkheads using standard PVC cement, so it’s probably not the worst thing you can use (however, let it cure overnight if in doubt!!)
Transition Cement can be found at just about any hardware store. It is light green in color, and opaque. It typically comes in a can with a green label.
Rule #2: Do not use primer on the ABS partThis is the most important rule!
Primer is not required, but it is also not recommended. Use primer only on the PVC part. If you want, you may wipe the ABS part clean with a damp rag or another non-solvent cleaner.
Rule #3: Apply cement to the PVC partDo not apply the cement liberally, as this can cause pooling; this generally doesn’t weaken the joint significantly, but it makes for quite the mess.
Do not apply cement to the ABS side of the joint.
If you think you need to practice, use 2 PVC fittings that you can throw away afterward. It’s a lot cheaper to do that than to mess up the scrubber parts.
Rule #4: Do not twist fittings back and forth when pushing togetherIf you twist the fittings back and forth as you push the parts together, this can cause voids and channels to form in the joint that can result in leaks.
This is actually a general rule for solvent welding plastic fittings that some are unaware of. When pushing the parts together, turn the fitting only 1/4 rotation in a single direction as you push the parts together, then hold the 2 parts still for 15-30 seconds and allow the solvent to set up.
The Slot Pipe is not reversible – it can only be oriented in the Growth Chamber in one direction, so you must determine which end the cap should be bonded to according to the way you plan to set up and operate the scrubber!