I'm going to redo the hot connection, after I monitor it for a while; and yes, there was lime on the threads. The drip rate there is down to less than 2 drops per hour. The cold connection has stopped dripping totally.

I considered using teflon tape, but since the risers had plastic washers at the tips, I figured those were there to seal the joint instead of tape. I'll redo it all if I need to, but would rather let sleeping dogs lie if I can.

@JeffWheeler - No mortar? I'm not sure loose stone blocks would be a good idea. But whatever. If one is concerned about settling, then build it short a bit, and wait a year. I do believe MOST of the settling should be done by then. Then top it up a course or two and make it level again.\

@FreeMan - What I meant is that if one end of the wall is low, and the owner/builder doesn't notice it, then when the next flood comes, the water will flow over the wall starting at its lowest point. Therefore it's necessary to FIND that lowest point and raise it up to a common level.

@statueuphemism - Overbuilding a few inches of course is a good idea, but the height of the wall is effectively the height of the lowest point. Why waste the extra height if it's not going to be useful?