first person ive heard say they work good, lots of threads on here downing them and from personal experience and comparing more than one to a really expensive ph meter i have never seen one close to accurate. i would fill a small pot with some soil and run some neutral ( ph 7.0 ) water threw it, then test the drainage. with a digital ph meter. you dont need an expensive one.... if the drainage comes out close to neutral soil should be ok. there are things you can add to the soil to adjust ph