Perlite and Ph?

Hey all,

I've been trying for weeks to figure out what is causing the ph in my res to constantly rise and after about 10 different tests on water at every stage in the system I've narrowed it down to the medium and/or something in the bucket with it. Just to let people know it is a 4 bucket system on a 25L/6Gal Res however I only have 2 plants atm as the other 2 seedlings damped off and died.

I ran 150L/40gal of ph 5.4-5.8 water through one of my empty 15l/4gal buckets that is connected into the res system, its filled with 100% perlite (no plant no rockwool etc) and still after all that water the run off is coming out with a ph between 5.9-6.4. The same as when I first started the rinse. I did also wash the perlite before putting it into the system with around the same volume of tap water until all powdery residue was gone.

I dont know if I just have to keep pumping ph water through it until it starts to balance out (I only gave up as it seemed like I was wasting water and not getting any reduction in the ph increases) or just deal with balancing the ph 4 times a day for each res. Either way its not much fun.

Any advice would be great.

Other info if helpful:

Water Ec from Tap: 0.3
Water Ph From Tap: 7.5-7.9
Aqua Flakes Nutes Added to Ec: 0.8
Balancing Agent: Ph Down - Citric Acid
Res Temps: 24-27C/75-80F (Maintained w Ice Bottles)
Plant Mediums: Rockwool 1inch cube in 15L/4Gal Perlite
Feeds: 15mins every 6 hours

Try maybe 4 times a day. Your plants may not drink that much but it will prevent your perlite from drying so fast, causing salt buildup, and burns and from there all sorts of weird ph shit.

I'm going through the same shit but in much smaller buckets and 4inch rw..

So for me it's a balance of keeping of the rw kind of wet and the perlite soaked. Next time try coco or just rw cubes in drain to waste.. This maintain a res shit is old news. I'm going coco 2 gal sq pots drain to waste next round.