What is TDS?

[jetchris]

I know it refers to RODI water. What does TDS stand for? How do you test for it. Can someone kinda break down the subject of TDS.

Thanks,
CHris

 

[jhutto]

total dissolved solids (TDS). Its all the stuff like minerals, impurities, chlorine, etc in your tap water. Its measured by a TDS meter. All the tap water has junk it in and for salt tanks you want to take all that out with near 0 TDS. Then you add the salt mix to it and get the right chemical content in a more pure environment. Does that help?

Joe

 

[jetchris]

yes thanks, where can i get a tds meter ?

 

[jetchris]

also if i am using an RODI unit shouldnt the water coming out be 0 tds ?

 

[nishant3789]

most sites taht sell RODI units will have them. avg price about 25bucks

 

[victor626nj]

yes

 

[nishant3789]

chrisjet;58773 wrote: also if i am using an RODI unit shouldnt the water coming out be 0 tds ?

yes.

 

[jhutto]

I got a hanna meter on ebay. Thats where several folks got theirs. It only a few dollars. You can then tell when your filter need changing on the RODI water. The catalogs sell them but they are more expensive. In the meantime if you want it tested, Cap Bay can do it.

 

[jetchris]

cool , thanks

 

[jhutto]

Here is what I bought and it works fine:

 

[nishant3789]

btw we also test it for free as well now.

 

[dannybradley]

This one has worked well for me for years. It goes inline with John Guest fittings. It's the same one Kent Marine packages with their units.

http://cgi.ebay.com/HM-Digital-DM-1-Inline-Dual-TDS-Monitor-Meter-DI-RO-DM1_W0QQitemZ280133893115QQihZ018QQcategoryZ20684QQrdZ1QQcmdZViewItem">http://cgi.ebay.com/HM-Digital-DM-1-Inline-Dual-TDS-Monitor-Meter-DI-RO-DM1_W0QQitemZ280133893115QQihZ018QQcategoryZ20684QQrdZ1QQcmdZViewItem</a>

And here's god TDS info:
[IMG]http://www.waterfiltersonline.com/tds-sources.asp">http://www.waterfiltersonline.com/tds-sources.asp</a>

 

[george]

Since the TDS meters test for conductivity, it really ought to be called a TDI (Total Dissolved Ions) meter. However, since the majority of TDS are organic salts, it's a relatively accurate measure of real TDS.

TDS meters can be used for an indicator of when it's time to change out your DI resin (beyond the color change) since towards the end of the DI life, the efficiency may drop off if you have a high output unit before the cartridge resin fully turns. Don't rely on a TDS meter for overall health of your RO system, though.

 

[jdpierce21]

The Filter Guys have a few to choose from.

 

[jhutto]

What color does the resin turn? New its goldish brown and mine is beginning to turn blackish brown. I changed all the other filters yesterday except the resin but now I am getting 8-10 TDs when I was getting 2-3 TDS. Was not sure if its the resins needing changing or the disturbance of the changing the 3 filters. Only ran 1 gallon thru it since I changed the other three filters. Been working for me for 5 months with water changes for a nano and a 90 gallon which I set up in February. Thoughts?

 

[george]

jhutto wrote: What color does the resin turn?

I think the color depends on the resin.

However, you should be getting zero TDS going through a DI filter. Your normal reading of 2-3 tells me that there's something wrong. Perhaps your testing container is contaminated. I don't know if there's a difference between resins, but it may be possible that you're using a less than perfect resin. In the same way that RO membranes have different rejection ratings, I suppose certain DI resins are better than others.

There are many reasons to stay on top of your RODI output quality. One that some overlook beyond the water's effect on the tank is testing. Less than pure RO water can affect refractometer calibration and many titration tests like calcium. It's not huge, but a little here and a little there adds up.

 

[jhutto]

TDS has been zero for months. Last week it went to 2-3 in a clean container so that is why I changed the filters. Think I will change the resins to see if I go back to zero. I like zero better.

 

[nishant3789]

maybe the tds meter isnt calibrated right?

 

[jhutto]

TDS meter only few months old. Its been 0 since I got it and calibrated it. It was time to change all out as I did lots of changes when I set the 90 g tank up and bought the RODI used so I did not now what "mileage" it had on the filter and resins. I changed the resin and its now down to 1. I will run some more water thru the new filters and resin to see if it get to 0. I did calibrate it when I got in a couple months ago. How often should you calibrate it?

 

[nishant3789]

personally i would calibrate it at least once a month.