RO Water fluctuation - need input

I have been have problems with RO water movements and am looking for input from people with knowledge in this area.

A couple of months ago my ro water ph was 7 on the dot, but in the warmer months the ph floats between 6.2-6.5 in the 55 gal drum I store the water. So when adding the nutes in my rez, I get a ph around 5.

I would like to continue to used the RO because my tap water is 320 ppm, and it seems that there is benefit that could be achieved. however adding ph up to my solution every day concerns me.

-I have a 24/7 meter and also used a cal/mag supplement (50 ppm)

I have never had this problem with tap water and am considering ditching the RO system for tap. However, if I was able to obtain some input from individuals with an understanding of why this is happening I may consider keeping the RO system.

How big is your reservoir? Most PH will go up as the plants take up the nutrients, I also usually have to add some PH up to get it around 5.6, but with 20 gallons I dont have to do anything else until after 4 or 5 days when I need to add some ph down due to those hungry plants.

While RO isn't at all needed, the pH of the water coming out of it should not wander far from 7. If falling below 7 (and the metering is not lying to you, calibrate often), something is making the water acidic. When in doubt, calibrate the pH metering, then clean, clean, clean.

Don't know what your storage tank is made out of, but it should be plastic. If it's steel or painted, those might have some effect on pH.

You could save the cost of the CalMag by switching back to tapwater. The RO is mainly removing Ca & Mg and you are having to replace it.

Keep the RO system, I'm sure it makes nice drinking water. It's just not needed to grow good plants.

I calibrate my meter every week and the drum i filter my water into is made of plastic. I clean everything regularly.
I just can't figure out why during this time of year my ro water is 6.2-6.4, when it was 7 three months ago. Its driving me crazy.

It'd drive me crazy, too!

Can you sterilise the unit with H2O2 to eliminate a bacterial or fungal colony in the machine as a problem? I'd try 10ml 50% grade H2O2 in 1L water. H2O2 will break down to hydrogen & oxygen in short order and thus should not hurt the RO unit.

Have you inquired of the maker? Maybe they have some insight.

I appreciate the input Al B.

I already tried cleaning the drum with no luck. The only thing I can think of is that the existing filters need to be changed. i will give it a try in the next couple of days and let you know.

If you think of anything else let me know. I am in ah.

Can't think of anything else. Change that filter and see what happens. Next step is to bug the mfr's tech support, I reckon.