Scott Hildenbrand wrote:

What's the soil like in your area?

Top 1 - 2 feet is fill (construction fill/topsoil) Below that is sandy
(In Fla)

Swampy area don't need to be near any heads. They could be anywhere the
line could break. But if your soil drains well then it's all together
possible that it's draining off.

Good Point, especially in the sandy soil below.

If you're lucky you'll be able to narrow it down to digging up a few feet at best to fix.

Especially with almost a 1/2 an acre

Either way, good luck on finding the problem...-
Thanks, Dave FL