Fire pit line full of water in winter

I have a NG fire pit on my patio, all concrete patio with line coming from the crawl space under house. During the rainy season (Nov-Mar) the line fills up with about 3-4 cups of water. In the other months the line is clear. If I vacuum the water out of the line the fire pit works fine for a few days, then the water returns. I never smell any gas and have shut off all appliances and pilot lights for several hours and found no movement on the meter. Our house is at the end of the block and lower than others and the patio is lower than the rest of my house. Do I have a leak under the patio causing ground water to infiltrate or could their be water or condensate coming from the utility in the line? I'm in California, PG&E is the utility company. Any way to remedy in either case? I have no control of the gas coming from the utility and I really don't want to break out my concrete patio.