grassott's dad
Member
Perlite has about a neutral pH of 7. If your runoff is way different than what you are putting in, that is because there are dry salts (from the nutes you feed) that build up when the perlite gets too dry.
For example, if you start with plain water with a pH above 7 and add nutrients and correct pH to 6.2, and your runoff pH is 5.5. That means you must have had lots of salts sitting around that were mixed into your most recent watering so your recent feed not only had a pH out of range, but was too strong. If the pH rose to 6.8, your probably not feeding your plants enough...
I never check run off these days, but when I did, my pH was always around 7.5ph. So does that mean I've never had salt build up?