RO/DI unit TDS sensor placement

[sdergar]

I have a Barracuda RO/DI unit and have also picked up an in line TDS unit. I currently have the inbound sensor placed in the feed line from the tap and the out sensor on the tube taking the product (good) water to my container. I've heard that the in sensor should be placed after the RO Membrane but before the DI unit? Have I got it setup right or wrong?

Thanks...Steve

[neilanh]

depends on what you want to monitor. I have mine setup just like you do, my outbound reads the final product.

Some folks prefer to see how much TDS the RO Membrane is taking out vs what the DI resin is doing. The DI resin will "clean up" whatever's leftover after the membrane, so to speak, so trusting the DI to do it's job some like to monitor the Membrane.

[Fishguy2727]

You can test your incoming water from the tap (not necessarily from the exact line feeding your unit) so you don't really need one before everything. By placing it after the membrane but before the DI you monitor the water coming out of the membrane which can tell you when to replace the membrane BEFORE your DI has also been used up. If you don't do it this way you will only know when things need to be improved after BOTH the DI and membrane have both been saturated/used up.

[Kurt_Nelson]

Originally Posted by Fishguy2727

You can test your incoming water from the tap (not necessarily from the exact line feeding your unit) so you don't really need one before everything. By placing it after the membrane but before the DI you monitor the water coming out of the membrane which can tell you when to replace the membrane BEFORE your DI has also been used up. If you don't do it this way you will only know when things need to be improved after BOTH the DI and membrane have both been saturated/used up.

Yup... agree.

[sdergar]

That makes sense to me. Thanks


Steve

[cmor1701d]

This is why I prefer a handheld tds meter. I can easily monitor tds at the tap, after the RO membrane, and most importantly after the DI.

The first two are for my curiosity. The last one is the important measurement as it is the only reliable method to know when the DI is exhausted and needs to be replaced.