If you can check the ph of your water, then you chack the ph of your soil. There are two ways to do it. You can dig down a couple of inches in one of your pots of soil, and take a soil sample, put it in a dish. Add some water(check the water ph first to see where it's at) and make a little mud. Now check the ph of the mud water. You could also water a plant with the water until runoff, and check the ph of the runoff.

Cheers,