RO/DI connection to TDS meter

[tigre44]

I bought a HM Digital dual TDS meter and want to connect to my RO/DI system but am unsure which lines to tap into. I believe that I connect the IN probe to the discharge of the RO unit and the OUT probe to the discharge of the DI unit. Are these the correct connections to tell me if the RO filters are going bad and the DI resin going bad?

 

[revhtree Verified Admin]

I have mine set up where the IN probe measures the water going from the water supply into the RO unit and the OUT probe measuring the water after it leaves the unit and heads to my top off tank.

 

[revhtree Verified Admin]

I am basically measuring my water that is straight from the tap, not the discharge from the unit. And the water after it has been purified.

 

[revhtree Verified Admin]

I am basically measuring my water that is straight from the tap, not the discharge from the unit. And the water after it has been purified.

 

[Eggs]

I'm getting ready to add the same TDS meter to my RODI, and plan on putting the IN after the RO, and OUT on the line (DI) going to the tank top-off - Essentially what you are saying.

 

[Paul_N]

I'm getting ready to add the same TDS meter to my RODI, and plan on putting the IN after the RO, and OUT on the line (DI) going to the tank top-off - Essentially what you are saying.

+1

That's how mine is set up.

 

[AZDesertRat]

You are correct, RO OUT and DI OUT so you monitor your membrane and DI resin. Measuring the tap water not as useful. I have two of the dual inlines but much prefer the handhelds like the HM Digital COM-100 which is more accurate plus gives me portability. I can test tap water, RO, RO/DI, between my dual DI canisters, my ATO holding tank, the LFS, bottled water etc. all with one meter. Inlines are dedicated to two points and cannot be used portable since they depend on flow past the probe. Plus they are not truly temperature compensated so are not as accurate, they sense air temperature not water tempetature like a handheld which is required for accuracy.

I want to know what the TDS is hitting my DI resin since this has a major effect on DI life and final water quality. Tap TDS will not tell me this.