Very strange indeed. Certainly possible that it’s buried below grade. There are ways to find buried pipes but you will have to pay someone to do that and it isn’t cheap. And if they do find it buried a couple of feet down then you gotta pay someone to put a riser on it if you ever want to access it. What a waste of money.
When the previous owners to this house built the casita on the property the supplied water to it by tee’ing into the main line for the house. Their plumber did a terrible job and caused a leak because it’s clear they came up short by a inch or two and then tried to yank the main PVC the get it closer to their pipe. Well they cracked the main line and then patched it using an IRRIGATION coupling … something not designed for potable water lines AT ALL. Then they buried their shame. Fast forward to me 10 years later always having water bills for years and year with some random leaks. Not huge, but unexplainable 2-3 CCF increases in months where the water usage should be low. Drove my self bonkers trying to figure it out. Finally got a leak detection company to come out, trace all the water lines and use a Helium leak detector to find the leak. This is what my plumber dug up underground -
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You can see the tee, how they yanked the line and then, in breaking the line, they patched it with an irrigation coupler …. FOOLS! Their shame exposed.
Well, $4,000 dollars later out of my pocket, I had my plumber fix all of it and bring isolation valves up to the surface so that in the event of a water leak I can isolate the casita from the main house and not have to worry about losing water. The original owners could have had the job done right by competent plumbers but their obvious mantra was to pay the least amount of money for everything and let someone else deal with the failures.