Hello guys, hope everyone is doing well. I posted a while back about replacing a P trap under my slab. I was able to cut the cast iron p trap out and attach a PVC trap using a ~4inch fernco coupling. I ran a ton of water through it and there is a small drip leak on the cast iron end. This pipe is roughly 14 inches beneath my slab (we’re on grade). As you can see from the picture there is ground water there from a bunch of rain and snow melting here in NJ so I’m wondering if a very small leak is going to be a problem. The cast iron I’m attaching to definitely has some rusty barnacles on it and is almost impossible to get smooth. I’m wondering if I should just leave it, or change the coupling, or attempt to smoothen the pipe more? Any advice you guys can give would be helpful. Thank you.