TDS question

ahiggins · Jul 24, 2016

hey all!
I finally put a tds meter on my rodi system! It's pretty cool lol but when do I need to replace chambers and how do I know which are bad?
I have the ro buddies with DI resin chamber.

120 tds going in, 0 coming out.
What's the max that can go out before you replace a chamber?

AZDesertRat · Jul 24, 2016

You need to know 3 TDS readings, tap, RO only and final RO/DI. I hope you didn't buy a dual inline meter as they are limited to two readings, lack the accuracy of a similarly priced ATC handheld and cannot be calibrated.
You change the RO membrane when the rejection rate, calculated using the tap and RO only readings, is no longer in the 96-98% range and you replace the DI when the final TDS is anything other than 0. You replace the sediment and carbon block filters every 6 months and you disinfect the entire system at least annually.

ahiggins · Jul 24, 2016

Well I definitely did buy a dual one >.<
So guess I'm going to exchange it for the 3 way tomorrow.
Thanks for the info! Very helpful

ahiggins · Jul 24, 2016

Oh how do you disinfect it?

AZDesertRat · Jul 25, 2016

No. No inline TDS meters period. Get the HM Digital TDS-3, TDS-4TM or AP-1 handheld. All can be had for $25-$30 and are 10 times the meter the inlines are.
Most legitimate RO vendors have published disinfection procedures or you can search my hundreds of threads on my personal disinfection techniques.

ahiggins · Jul 25, 2016

To be clear...I would have to disassemble my hoses to use these meters every time to check it...
Why arent the inline meters "good"? Im going to check out more on this.
Thanks

eg8r210 · Jul 25, 2016

AZDesertRat said:
You need to know 3 TDS readings, tap, RO only and final RO/DI. I hope you didn't buy a dual inline meter as they are limited to two readings, lack the accuracy of a similarly priced ATC handheld and cannot be calibrated.
You change the RO membrane when the rejection rate, calculated using the tap and RO only readings, is no longer in the 96-98% range and you replace the DI when the final TDS is anything other than 0. You replace the sediment and carbon block filters every 6 months and you disinfect the entire system at least annually.

I have a question about the inline meters, do both have to be connected to get an accurate reading? I ask because I have two inline meters. Right now I am using one and the one side is right before the membrane and the other side is directly after the membrane. I am getting 110 TDS into the membrane and 5 out (also burning through DI) so I am going to buy a new membrane. I would like to use my other inline TDS meter right after the DI but I would only need to use one of the leads. By installing it this way will the meter calculate correctly?

twilliard · Jul 25, 2016

ahiggins said:
To be clear...I would have to disassemble my hoses to use these meters every time to check it...
Why arent the inline meters "good"? Im going to check out more on this.
Thanks

A tee and a valve at each test point is the best way to do this

You already have the tee as this is where the in lines go.
Put a peice if tubing at each and a valve on the end

ahiggins · Jul 25, 2016

twilliard said:
A tee and a valve at each test point is the best way to do this
You already have the tee as this is where the in lines go.
Put a peice if tubing at each and a valve on the end

Ok, I was wondering if I could do it that way too.
I would need a tap (or the "in") reading, an "out" of the RO chamber, and an "out" of DI chamber. So 3 total. Correct?

twilliard · Jul 25, 2016

ahiggins said:
Ok, I was wondering if I could do it that way too.
I would need a tap (or the "in") reading, an "out" of the RO chamber, and an "out" of DI chamber. So 3 total. Correct?

Yes and when you have that setup you are already in the position to truly know the condition of your system

ahiggins · Jul 25, 2016

Thanks for all your help everyone!

ltrace · Jul 26, 2016

I have a RO/DI with a dual inline meter. It would help me if someone had pics of what you are referring to. Maybe a pic of the whole setup.

twilliard · Jul 26, 2016

ltrace said:
I have a RO/DI with a dual inline meter. It would help me if someone had pics of what you are referring to. Maybe a pic of the whole setup.

You mean for the test valves?

ltrace · Jul 26, 2016

yes and how it is incorporated into the system I have already.

AZDesertRat · Jul 26, 2016

If you have an inline already hooked up, simply remove the IN and OUT probes from the tees, slip a short piece of 1/4" tubing in the tee and put a ball valve on them. Now you not only have a place to sample TDS accurately with a ATC handheld meter, you also have a place to draw RO only water for drinking and a place to flush out TDS creep before it hits the DI each time you make water.
The two biggest issues with inlines is they do not sense the water temperature with the probes, the temp probe is inside the fat part with the little rectangular opening so it reads air temperature so is not ATC compensated. I have cut a probe apart to see this. This can lead to significant inaccuracy since air and water are rarely the same temperature.

The other is they cannot be calibrated which seals it for me.