You should be OK, I think...what he said. I find that if you use ROwater, once you mix in 3-part...you almost always get real close to 5.6-6.0 and I check mine every time... but if my ph meter broke and I was still using 3-part; I would trust it, until I got my PH meter..In closing the 3rd argument above was...GET a PH meter! LOL...lw