TDS reading for RO/DI

[S!mon]

Just installed my Kent Maxima RO/DI deluxe unit this weekend, and my TDS reading for incomming water is 245 ppm. More importantly, the TDS for production water is 15 ppm. Should the ppm for production water be lower, or is this acceptable? Thanks.

 

[Buckeye Field Supply]

No - You'd not want to put 15 ppm water in your reef tank. Let's assume the system is set up right, and the resin is still in good shape.

Did you take your TDS reading in a sqeeky clean glass container?

Did you test the DI water first, or was the container already wet from checking the tap water tds?

Is your tds meter calibrated?

Did you allow the system to run a few gallons through before your tested the DI water tds?

Russ @ Buckeye Field Supply

 

[ChrisRD]

Russ makes some good points above. Basically, if the unit is working properly and the sample is collected properly you should get 0 TDS water from your RO/DI unit.

 

[S!mon]

My system came with an in-line (incomming and product water) TDS meter. I have not calibrated the meter yet, there were no instructions in doing so. I discarded the first ten gallons of water produced. The water feeding the system seems to be warm, will this affect performance of the unit?

 

[Buckeye Field Supply]

Wher are the tds probes positioned? Before and after the RO? After the RO and after the DI?

How warm is the water? Something in the high 70's would be grand.

Have you checked to see that the probes on the meter are aligned properly?

Russ @ BFS

 

[S!mon]

One probe is positioned before any filtration at all, just out of the tap. The other probe is located at the end of the entire process. The probes are lined up correctly with the marks per the instructions. Water temp. is greater than 70F. Supply line is warm to touch, I'd guess upper 80's. I know that I have the cold line, just a strange plumbing problem in basement. Instructions for meter said to callibrate with NACL, but no instructions as to how...Thanks for your help Buckeye.

 

[Anonymous]

That water is pretty warm there. The warmer the water, the more ions going to pass thru the RO, so you will get less pure water, but at higher yield.

As to the purity, it should not be a concern since you got the DI after the RO. Just something to keep in mind.

As for the TDS reading, most of the meter out there in the hobby are notoriously not very useful, particular when it come to ultra-pure setup such as RO/DI. Most are designed for the RO-only, or used for the hydroponic community. At any rate, you need to verify that the meter is doing what it suppose to do, instead of worry about the water quality. Get a good calibration (quality meter will come with good instruction, BTW), and test it on a know sample of low conductivity water. If it give correct reading for the low conductivity water, and still give you high reading for the output of the RO/DI, then you should do more trouble shooting on the filter.

 

[S!mon]

So should I take some of my water to my LFS to test, or should I by a good TDS meter?

 

[Buckeye Field Supply]

In our experience, a handheld TDS meter, some of which can be had for less than $30, is sufficient for this hobby.

Russ @ BFS

 

[S!mon]

Wow, the only TDS meters I have seen were for $150 or so. Can someone please tell me where I can get one. Thanks for everyones help.

 

[trido]

Here's one. http://www.marinedepot.com/md_viewItem. ... uct=RO1351 I picked one up at my LFS for about $40.

 

[ChrisRD]

...and another: http://www.buckeyefieldsupply.com/showp ... ecials=149

 

[Anonymous]

Again, being a water nazi in a way, the TDS meter is alright for RO, but for RO/DI, it is certainly not as useful as you think. I am not saying that they are useless, just that you need to know what it is good for, and what it is not intended to be for.

 

[S!mon]

So how can I be certain that the water I am producing for my tank is "pure" ? I still can't get my TDS below 14ppm anyway...anyone want to but a slightly used RO/DI system lol. :evil:

 

[Anonymous]

What you need is a "standard" to test your TDS meter. SpectraPure's TDS meter that only give you a red LED actually can be better than other gadget that have fancy LCD display when it comes to RO/DI. Ask people in your local reef group and see if any of them has a decent conductivity meter or resistivity meter that you can borrow to test your water instead of a toy TDS meter. You just need to compare your TDS meter with a profession meter to make sure it works well for low TDS reading ("0" to 5ppm range).