Question:
I've just replaced the the filter element in an under the sink RO unit and I've encountered two problemsThe large plastic cylinders are extremely difficult to get off. First, my plastic Filter wrench broke and then I was able to remove the cylinder with a large oil filter wrench - but it took a long time and obviously loosened other connections. This seems to be because the whole RO filter assembly is loose, therefore there is no way to apply leverage (like you would on the similar whole house water filter that's built into permanent piping). If this were a part on a car, I'd spray WD-40 on it and let it set over night. But I don't want to do that on a drinking water filter. Is there another type of lubricant that I could spray on these cylinders before I try to loosen them next time? Any ideas on how to get better leverage while holding the RO assembly in one hand, and turning the filter wrench with the other hand?

Answer: It sounds like a John Guest type fitting, you just push the tubing into the fitting. To get it out you shut off the water and bleed the pressure then push in a collar against the front of the fitting and then as it's in you pull the tubing out. If you visualize a U slid down the tubing toward the fitting you have the concept. Holding in the collar while pulling the tubing out is a trick...

You use another housing for leverage while 'pinching' it and the filter together, it's all in the angle. Make the wrench and housings into a V shape and squeez the two together, using each other for leverage against the other. See knowing all this stuff and the tricks is why we get paid to bucks to do it. That and having the liability if something breaks.