TDS question on when to change RODI

[Fishingpcola]

So last night I replaced the membrane and the DI. I ran the system for 1 1/2 hours into a 5 gallon bucket and discarded. I hooked up the line to the resevior and filled up over night. This morning as water was still running the tds were 25ppm into the DI and 23ppm out of DI. Could the meter be that far off from calibration? I would expect the variance to be 1-3ppm difference. I did reposition the ball valve before the RODI. I expect my water bill to go down now!

 

[Randy Holmes-Farley]

I expect the DI is depleted, and there is no reason to suspect problems with the meter that I can see.

 

[Fishingpcola]

I expect the DI is depleted, and there is no reason to suspect problems with the meter that I can see.

Randy, you misread. I replace with a new membrane and new DI and the unit is at 23ppm.

 

[Randy Holmes-Farley]

Does it read 23 ppm TDS in air?

"Calibration" is not generally an issue for reading 0 ppm TDS. It may be broken and stuck at 23, but zero is zero. It is only the slope that changes with calibration. If it reads 0 ppm TDS in air, then there is a good chance the DI is depleted or somehow water is getting through it untreated, whether it is new or not.

Is the DI horizontal by any chance?

 

[Fishingpcola]

Vertical. I replaced it last night with DI from BRS.

 

[tmz]

I use an in line meter between the two di cartridges and a portable hand held meter to check other outputs. Works for me.

 

[Fishingpcola]

I found a local store with a tds meter. I will verify tomorrow.

 

[Randy Holmes-Farley]

Did you try it in air?

Were the most recent values in line? When not measuring inline, a little, tiny, tiny bit of contamination in the collecting container can drive up the TDS.

 

[Fishingpcola]

No I have not tried it in the air. What should an air rate give?

 

[Randy Holmes-Farley]

Always 0 ppm TDS.

 

[Fishingpcola]

I have pulled the sensors out and dried them off with a paper towel and the numbers are either in the 30's or 40's depending which sensor you are looking at. I called HM Digital and they told me should be zero and to send it in.
Thanks Randy.

 

[Randy Holmes-Farley]

:thumbsup:

Sounds like a good plan.

Good luck.

 

[Fishingpcola]

Now I need to repair the auto shutoff valve. Never ends!