@sbbeebe
Here is a
link to a post I have a few pages back, might want to review for future issues. If you don't use your Zymatic supplied keg for fermenting, I would highly suggest removing the poppets/springs from the keg posts and the Zymatic connections. There is no need to have those objects in the path of the wort.
Now, the Zymatic is designed to overflow off the back edge of your step filter, where the rubber plugs are, and into the adjunct compartment. Having wort go over the back edge is a normal situation and this, in and of itself, shouldn't cause a leak. However, due to the rubber plugs, this is a notorious leaking point and is just bad design. Use plenty of keg lube on these rubber plugs (more than you think you need), make sure the Zymatic is level and make sure the Duck valve is fully seated into the step filter (I've seen it back itself out and get stuck on the drain pipe) and inspect for cracks at the Duck valve.
If you look at your step filter you will notice the back edge of the grain compartment (where the rubber plugs are) is just above the top screen and just below the top edge of the step filter itself. If the Zymatic is level, you shouldn't get an overflow over the side of the step filter, by design. When running the Mash, the liquid level at the bottom of the step filter should be at or just below the lower screen, I have seen both and indicates the drain pump is removing the proper amount of wort and you don't have a stuck mash. Having the wort below the lower screen too far, indicates that the wort is not passing through the grain bed quick enough and is mostly going over the back edge of the step filter. If this happens, add more rice hulls to your grains to allow more wort to exit at the bottom, rather than overflowing. If this is the case, you're leaking from the rubber plugs IMO.
If all situations are normal, you could have an issue with your drain pump. Don't let PB tell you otherwise, I have seen it first hand and solved this problem without the aid of PB CS. I had a constant problem with the drain pump surging and allowing the wort to backup into the grain bed during heat to boil, eventually overflowing the adjunct compartment and over the side of the step filter and onto my table. Only after dismantling the Zym, removing the drain pump and opening/cleaning the pump head, did this problem go away. PB CS was correct in that the diaphragm was not bad, but it definitely needed a rebuild/clean. This is probably a rare instance so don't jump immediately to that conclusion.
PB CS will always error to the side of a cleaning issue or a block in the drain line for these types of errors, but if you look back at the pics I posted on earlier pages, you can see how simple the drain loop is. This is a big reason why I removed the poppets and springs in both the keg and the connectors. If while running, you see the wort through the test port surging and having a ton of bubbles, you most likely have a drain loop issue (this is also why I do not recommend you remove the test port). Could be an air leak at the Duck valve allowing air to enter the drain line prior to the pump, a crack in or around the Duck valve, or it could be a husk has made it's way into the drain pump diaphragm and is allowing air to pass from one chamber to the next.
If this is the case, you might try a good Deep Clean, see the link I posted, as this "may" remove your blockage by soaking the husk enough that the pump can expel it. I wouldn't recommend dismantling your Zymatic unless you are mechanically inclined and it's a last resort. PM if you need help with that, I've done it numerous times and my Zym is better for it.
If everything is working as expected, the Zym is level and you don't have any cracks, I would guess it is the rubber plugs 9 out of 10 times.
