R/O PH levels

I have been using R/O water in my 120 gallon discus tank for many years with no issues. I recently changed filters as I have done I the past. My PH has been consistently at about 6.5 forever. After this filter change however, my PH is coming out the R/O system at 7.5 plus. I have flushed the unit several times now with no success.
Any ideals?

 

I have been using R/O water in my 120 gallon discus tank for many years with no issues. I recently changed filters as I have done I the past. My PH has been consistently at about 6.5 forever. After this filter change however, my PH is coming out the R/O system at 7.5 plus. I have flushed the unit several times now with no success.
Any ideals?

Have you checked the TDS? Be good to know the new filter is working properly.

 

You say you changed the filters but what about the membrane? How long has it been since you changed that?

Edit: I should have mentioned the membrane is what affects the PH as it decriminalizes the water.

 

I have not checked the TDS.
I did in fact change the membrane which has been about 2 years since the last membrane change.

 

Normal life of a membrane is 1 - 2 years depending on water quality. I would suspect that 1st for your rise in PH levels. If you just changed it, check to make sure it is seated properly. If that is okay, then it may be the membrane itself.

Is it a different brand?
Is the membrane the same size micron?

The membrane is what affects PH and is what causes the PH to drop. If the membrane is not working properly or the correct micron size, you can have higher PH.

 

I did have an older system (Whirpool) and could not find original filter replacements which lead me to purchasing after market replacements. So, I actually upgraded and installed a new unit (AC Smith RO 4000) unit, but with the same results. The only thing I did not do and wish I had done was to reinstall the original membrane and test the PH prior to replacing the unit which I could do fairly easily.

 

So are you saying the old unit had higher PH levels and the new replacement does as well?

 

Yes, I am so confused at this point.

 

Okay, so two different RO systems test with higher PH. What is the PH of the water source. Let's get a baseline to compare.

Also, What about your test kit? How old is the PH test kit?

Edit: What type of test kit?

 

PH at tap is extremely close to output of R/O system now. I am using a API solution test kit. I have used this same test kit to measure the PH from the aquarium itself and results indicate the test kit is measuring correctly.

 

I am no expert in this area by any fashion. Trying to work the problem eliminating the obvious and seeing what's left to investigate.

Hopefully someone who has experience or works in this area can chime in and provide input to help understand better.

When you provided information that you had two RO systems testing same results and your source water tests close to the RO water keyed in the thinking that something else is going on and more research and detective work was needed.

I have been doing a bit of reading on this and found the below information to be interesting and is something to consider.

What if something has changed with your water source. The changing of the amounts of organic or inorganic compounds added to water will change the PH to your source and RO system.

The next couple paragraphs are from some two sites you can go to to read up on how water and PH are affected in a RO system.

Here is a link that gives a short summary on how PH is affected by CO2, HCO3, and CO3.
Water quality information - Is pH of RO permeate really lower than the feed-water pH? | APEC Water

Here is a link that discusses how CO2 and the membrane function and it's affect on PH: Reverse Osmosis Water and pH

This is a very confusing issue that once you ruled out your RO membrane and test kit leaves the water source.

What are your thoughts on this.

 

Some good news at least but still confused. The water from the ro system that has sat for 24 hours is reducing in PH significantly. Same high PH measurement currently straight from the system. I thought about water source also but what a coincidence if the water source changed exact time as filter changes. Oh well, will keep testing. Would the new membrane and/or filters take time to adjust and react properly? Never had this problem before but hoping the problem will self correct.

 

Some good news at least but still confused. The water from the ro system that has sat for 24 hours is reducing in PH significantly. Same high PH measurement currently straight from the system.

I think this confirms the CO2 leveling is affecting your PH test readings and there is something with your water source.

The pre filter and carbon filter are taking out contaminates of a certain size and larger. How well they polish the water before the membrane depends on the micron of the filter. Do you know what the micron rating those filters are?

Hopefully something like 0.5 and 0.1 micron. I tried looking up your filter and seeing what micron rating the filters and the membrane are, but had no luck. The size (micron) of the filters would be nice to know. It matters as it will affect the membrane performance and longevity.

The membrane is what affects the PH not the other filters.

How much water have you processed in the new system? There may be a need for some settling or break-in to the system.

You should also check TDS input and output. This will tell you the efficiency of the new system. If the readings are high, you may see improvement after running more water through it. I have had to do that after changing membrane and filters.

 

The only mention I found about micron performance for my particular unit is: "Aside from chlorine, RO can nearly eliminate any remaining lead, mercury, fluoride, and other particles down to 1 micron in size".
A TDS tester is on my list of to do's. I am in process of purging again for a min of a 24 hour period. About 1/2 way through, I have seen some improvement in the PH level measurement.

 

I'll bet it's a 1 micron system. That's good for freshwater. I used 0.1 and 0.5 for my marine system but switched to 1 micron for fresh water.

Not sure if this has any bearing but I've come across discussions in other threads and forums where people have had pH issues around times when they had a lot of rain. You would not have had recent heavy rains in your area? Looking at the off chance the water company could be adding additional elements to the water.

I'm pretty much at a lose of where to go after this. It does look like a pH leveling issue but what is causing it is the mystery.

 

Ahhh, not sure about the validity of PH associated with rain but I guess it could make sense and we have had a significant amount of rain over the past couple of weeks.