For a while I hoped "ok it was a wet year this is just seepage from the hill coming up here" but get into dry summer and it didn't change and I knew the truth - pipe leak.
Last year I replaced our irrigation pump. Previous one was noisy and had experienced at least one too many frosts without being drained; I'd rebuilt it twice over the years but clearly a rebuild wasn't going to help the basic issue, it only built a bit over 40psi and that just didn't cut it at our upper garden which is up the hill. I have the new pressure tank for 70/50 now and the new pump is a submersible, sitting in the holding tank, so it's almost entirely silent - a slight humm audible from a couple feet away, probably from the vibrations on the pipe.
Anyways, pretty sure that that psi upgrade popped a joint, and after a bunch of probing with rebar and then hand digging to verify, I used the backhoe and found the culprit:
on the right is the 2" PVC coupling, and to the left you can see the 2" PVC pipe that someone 35 years ago read the glue instructions which said "primer not necessary with new pipe" and believed it. My guess is that this has always leaked just a bit but that the new pressure popped it further loose.
The ground there has an ugly clay layer and I didn't want to make a mess all over the surface - not to mention rocks for the mower to hit, so I dropped the loader bucket and every scoop coming out of the ground was dropped into it; when it filled up I went over, grabbed the bucket, and dumped it on a nearby grassless hill which shouldn't be too much effort to get the dirt back for filling afterwards.
I was very tempted to take the teeth off of the bucket as I was concerned I'd hook the pipe with them, and thought I could get a closer dig without them (they aren't exactly needed in this glop).
Very tempted to get a 6" trenching bucket -- anyone with a Branson BH have one? - if so, where did you get it? - I see bxpanded.com has one but I'm not sure I'm $417 ($379+shipping) tempted.
The actual repair in case you're interested, I used a compression coupling. I suspect that they introduce a significant amount of turbulence but that's not a huge concern in this application; the fact that no glue is used and you don't even need to dry the pipe - cleaning it is needed still of course - but you can go full pressure as soon as it's put together instead of waiting for the glue to fully cure (usually give glue an hour actually but...); it's much easier than digging up enough of the pipe to be able to flex a regular coupling into place, and cheaper than using a union - and requires much less accuracy as well. Just need to cut out no more than the center part of the coupling can span, and lift one end of the pipe up just enough to slip it over... see the pics you get the jist. Hand-tight was plenty - immediately turned the water back on and no leaks!
