Fantastic; glad it wasn't something more serious/costly :)

Well, I won't be 100% certain until time passes.

But - and I forgot to mention - he did leak check it and found nothing aside from that valve.

That was probably it all along. Sometimes you get lucky and the smallest thing is the only thing that's wrong!

Yes, thank you, I hope it's just that valve.

Took 6 1/2 years to drain to ~ 50%, so it seems plausible!