The thing works as is. If you follow the instructions, and use NC, normally closed valves, then the glycol does not flow backwards, and no check valves are needed. Planning the line length is discussed in detail, and when you follow the instructions in the thread, it works fine.
Issues are:
1.) potential for corrosion on the cheap SS hydraulic QD connections. This can be overcome with corrosion modifiers in your glycol solution. Many products, such as the Dow brand, include this.
2.) the plastic lid is difficult to obtain airtight seal and also to clean behind the inverts lip. This can be overcome by using stainless (duh), or modifying the opening and making custom lids from HDPE plastic as is posted by some users who have done this mod. Ultimately, this is a necessary mod in my opinion.
the overall design is excellent in my opinion, with just a couple of shortcomings. I think that there are many sanitary fittings used where sanitary fittings aren't necessary or truly sanitary anyways because of exposed threads, particularly the lid.
One other issue as pertains to the the lid and coolant fittings is the possibility of pressure lock. As you recall, heated liquids expand, and then contract when cooled. If you are fermenting beer at temps below room temp, then rack off the beer to conicals after dumping yeast you must be aware of the coolant connections to the hydraulic QD connectors. If you disconnect them, as the coolant inside the closed system in the coil warms to room temp, you might be unable to connect the hydraulic QDs back onto the coil because it is now pressurized because the coolant has expanded as it has warmed. The worst case is when you cold crash, rack, disconnect, then wash with hot PBW/CIP ball.
One workaround is to leave the efferent limb of the coil always connected to the QD, with ample polyvinyl tubing length to unscrew the lid while still attached (so as to connect the CIP ball). The efferent limb connects to the manifold on the return side and the ball valve position has no impact on the coil pressure, which can freely equalize pressure with the manifold pressure.
Another potential issue is reservoir volume. Be sure to have a fairly large reservoir for maximum efficiency and cooling potential.
TD