TDS level in RO/DI water?

[fishresponse]

Hey guys

What's the acceptable level of TDS in your RODI water? I'm getting about 9-13 depending on the time of day. Is that bad??

 

[fishresponse]

Anyone?

 

[Joshz400_03]

I've pretty much read everyone usually gets around 0. How old are your filters?

 

[insomniac2k2]

replace filters when you get anything but 0. It also helps to run a T and ball valve on your RO side to drain the water sitting in your filters for a while before if goes through your DI (expensive). Your Di will last a bit longer this way

 

[Essencereef]

I have a rather clever way of running my RO/DI system:

Install an in-line TDS meter, one probe after the membrane, and one probe after the first DI cartridge (if 2 are used like in my case) If your TDS leaving the membrane gets higher than 10-20, there's something wrong with membrane (good membranes let only about 2-10 TDS out where mine puts out 2) If your first DI cartridge reads anything above 0, replace it. But always make sure your membrane puts out as little TDS as possible (depending on quality of the membrane)
KEEP IN MIND:
Once the unit is turned on, your initial TDS readings on in-line meter will be really high (20-200) due to osmosis (where membrane stands by without being flushed), wait for 1-5 minutes to get accurate reading on in-line TDS meter.

Hope this helps! ask away if you need more info!

 

[NatureNerd]

+1^

When I first start water flowing through my RODI it is a little high but it settles to a low value in a minute or two. I start to use the water after I run my system for ten minutes. At that point, I get a reading of 0.2 - 0.4 ppm. If it ever gets to 1.0 ppm I will replace membranes.

 

[The Lance]

Just yesterday I started to make some water, but as soon as I turned on the water the tis read 43. I switched the first two filters out and it dropped down to 0.

 

[Buckeye Hydro]

Remember that your prefilters (all the filters that touch the water before it gets to the membrane, typically a sediment filter and a carbon block) have little effect on TDS.

Nearly all dissoved solids are removed by the membrane, and the remaining TDS is removed by the resin.

Here are some specs on just how much of the TDS membranes remove (referred to as "rejection rate")

So the absolute number (ppm TDS in RO water) isn't the issue - it is the percent of the TDS in the feedwater that the RO removes. So someone with 1200 ppm TDS feedwater might be happy with 36 ppm RO water, while someone with 46 ppm TDS feedwater might shoot for 1 ppm TDS RO water.

Regarding the TDS in your DI water - change your resin when you see anything other than 0 or 1 ppm.

Russ