|
|
|
|
|
#1
11-02-2009, 03:16 PM
|
|||||
|
|||||
Is zero tds possible with RO only?
I'm in Calgary btw. My dual stage meter shows the source water to be about 280 (though I just dipped the inline probe in a glass of water to avoid making more cuts in my pipes to make sure the meter showd anything other than 0). I'm getting a reading of 0 without running DI. The unit has 5 micron sediment, 5 micron MATRIKX CTO/2 carbon and then dow filmtec 75 gpd membrane.
With 98% rejection rate I was expecting around 280 x 0.02 = 6 or so When I first set things up btw I was getting a reading of 1 after the RO but after 10 min or so it read 0. Last edited by lastlight; 11-02-2009 at 03:25 PM. 
|
|
#2
11-02-2009, 03:28 PM
|
|||||
|
|||||
|
Yeah it's possible the DI actually does very little, will usually drop the TDS by around 10ppm at most. I've setup RO systems in Calgary before and got 0 without the use of DI.
280 does seem awfully high for Calgary though, but it could just be your location. It likely depends on what kind of solids you're dealing with, perhaps the pre-filters are doing a lot of the work prior to it hitting the RO membrane. It would be interesting to compare TDS before and after the pre-filterers.
|
|
#3
11-02-2009, 03:30 PM
|
|||||
|
|||||
|
Hmm, my source water shows a TDS in the mid 200's as well and my system is similar to yours, 75 GPD. RO TDS gets down to 1, occasionally 2, but I've never seen it at 0. Source water comes from a local lake and it's considered somewhat 'hard' due to the makeup. I've checked my source water both with the Dual TDS meter and a cheap handheld. There's a discrepancy of about 30 to 40 with the Dual meter having a higher reading than the handheld for source water TDS. I'm inclined to put more trust in the Dual meter, since I used both probes and they were within 1 TDS in their readings.
Did you check the source water with both probes? If not, might be worthwhile as a comparison and to instill confidence in the reading, although an accurate reading at a TDS of 280 does not necessarily translate into an accurate reading at the lower end of the scale. That certainly seems to be a concern with refractometers in many posts & threads. Pretty sure the Dual TDS meters have a calibration adjustment on them, so it may be an idea to look into that. Or, maybe the makeup of your source water is such that the solids are readily separated, who knows. Hopefully some fellow Calgarians will check in with their experiences.
__________________
Mike 77g sumpless SW DIY 10 watt multi-chip LED build  http://www.canreef.com/vbulletin/showthread.php?t=82206
|
|
#5
11-02-2009, 03:55 PM
|
|||||
|
|||||
|
Whoa 16 to 20! Your membrane will last a lifetime lol.
The meter I think is much more acurate with water flowing past the probe contacts. Like I said I only dipped the probe into a glass of tapwater so there was no flow. The unit is not quick conenct fittings so I *really* didn't want to bother with making another cut and then redoing the connection later. I'll Continue as is for now since it seems that things are ok. I'm sure these meters are not THAT accurate but whatever I'm getting out is very low in tds compared to the source. Good enough right now I need SALTWATER!
|
Hybrid Mode
