R.O. Water and ph??

Wtf is going on, i have 2 hp pen. im trying to ph plain water and both pens are jumping up and down by like .5 up and down.

i dipped both in ph 7.0 and they are fine? what do you think?

You cannot accurately measure the pH of R.O. water as it has very few carbonates. You need a purpose built pH meter and they are NOT inexpensive!!

Yeah what he said.

You don't need to PH ro water anyway, PH it after you add your nutes. Otherwise just use it straight up. It has basically no buffering ability due to being filtered so it pretty much conforms to whatever ph your medium is.