Dual In-Line TDS Meter

[xabo]

Can some post a picture/diagram as where to place the connections on a dual in-line tds meter? Thanks

[Origami]

Normally on either side of the DI resin stage. The input probe basically reads out the TDS of the RO membrane output, while the output probe reads out (nominally) the 0 TDS output of the DI stage.

[xabo]

I have the "in" probe between the out of the RO and the in of the first charcoal filter and I have a reading of 166 while the "out" probe coming out of the di is reading 0.

Edited December 6, 2012 by xabo

[Origami]

It's better to move the "in" probe to the clean water output of the RO membrane. This way, when the membrane rejection starts to fail, you know it. With the typical 75 gpd membrane that we use in this hobby, you should see at least a 95% rejection rate. Thus, if your source water is 200 ppm, then you should see it settle in at less than 10 ppm come out of the membrane after it runs for a minute or so. When this is no longer the case, it's time to replace the membrane (this takes 2 or 3 years typically).

 

Right now, you have no visibility into how the membrane is performing.

[xabo]

Pardon my ignorance but where is the clean water output of the RO membrane?

[xabo]

Okay I found it. My source water has a TDS of 192 ppm and the "in" probe reads 001 ppm. thanks for the replies.

[Spelter]

Not to thread jack but I have my press gauge on the water feed inline. Reads about 45 psi is this a problem?

[smallreef]

Should be 60 for optimal output..all low pressure is going to do is take longer to make water...

[xabo]

You might want to get a booster pump.

[Spelter]

Does the location I have it at before any of the canisters matter?

[Origami]

Does the location I have it at before any of the canisters matter?

Not sure exactly what you're asking, Spelter. It doesn't matter where in the line between the RO output and the DI canister that you put the input probe, but is does matter where in the sequence of canisters you put the probes as the measurement at different points tell you different things. The typical probe placement is as follows:

 

Input probe: Just before the DI stage. That is, on the line between the "pure" RO output line and the DI resin canister.

Output probe: On the output of the DI resin canister.

[xabo]

Does the location I have it at before any of the canisters matter?

Edited December 7, 2012 by xabo