EKO 40 Inlet and Outlet leak

I had a similar situation with my EKO 25 when I installed it,I believe they have European thread without a taper ,I had to redo mine with lots of pipe dope and tape and a lot of muscle.If I had to do it again I think I would have cut the threads off and tried new thread with a hand threader.If you try tightening more make sure you use 2 pipe wrenches so you don't twist the nipple off of the boiler

Your dealer didn't provide you with transition couplings with straight threads on one end and tapered on the other?

I had the same problem, very slow leak . it eventually went away

I'd bet it's the tapered vs non-tapered thread mentioned above. The easiest fix? Put a 2' pipe on the end of your pipe wrench and give that thing hell. I bet you've already mucked up the threads on the output pipe so if it were me, turn it down a few more turns and see what happens.

If you're going to pull it apart you can get the proper fittings from Grainger.com for a decent price. I beleive what you're looking for is British Standard Pipe or British Pipe Thread (BSP or BPT) on the EKO side of the fitting and the NPT on the system side. Easy fix if your threads are undamaged.

I had a few annoying little drips after I got my stuff put together. Had a couple that were little seeps on the boiler tappings when the boiler would go cold, sounds something like your issue.

I added a bottle of Gunk Boiler Seal and have not had one drip since.

If you want to follow up on that kind of thing, search for a thread with 'boiler stop leak' in it. I was suspicious it would work, but a year later still no drips & everyting still working as its supposed to.