TDS IN=148 OUT=9. Time to change cartridges?

[Armando]

I finally got some time to install the TDS meter from the group buy.

Getting IN=148 OUT=9. Do I need to change cartridges? All of them? Please say "No", I already have too many things I need to do

 

[me2003]

I use a conductivity meter and here is how I do the math.
For a RO there are many variables around 90-95 is OK.
With DI and RO I think you can get 99. I am not sure how
others calculate it and it may vary by water source.

9/168*100=6.08%

100-6.08=93.92%

 

[PenMan]

Is that one of the dual in-line TDS meters? Mine runs about 5 higher than the calibrate hand held. I just figure this in. Also in the unit has been sitting for several days, run a cup or two down the drain, it will be higher than you want

 

[clamm]

armando, increase your rejection rate.

 

[NateHanson]

I wouldn't go messing with rejection rate until you first confirm the reading with a second meter, and then replace your cartridges and flush the membrane. Finally, I'd start messing with rejection rate after all that didn't work.

 

[nunofs]

Armando, are those readings for tap water and after the DI? If so, I'd recommend you try getting a reading for the RO water (ie, before the DI)... because that's where you can figure out exactly how much work is being done by the membrane and much much is being left for the DI to remove... then calculate efficiency = (TDS_tap - TDS_RO) / TDS_tap * 100... if it's anywhere around or above 90%, the membrane and all the filters before it are doing their job and you'll only need to replace the DI resin... if it's lower than that, then you can start worrying about replacing cartridges.

Nuno

 

[nunofs]

And btw, I installed my dual inline meter from the group buy to read after the RO and after the DI, and I read the tap water TDS with a handheld meter... personally I think that it's more useful to know the TDS of RO and DI than the TDS of tap and DI.

Nuno

 

[NateHanson]

Great points Nuno. I think that's a great way to use the dual meters. Have you found yours to be accurate when compared to your handheld meter?

 

[Syris]

Armando,

Check it out http://216.235.242.50/forums/showthread.php?t=9792

Now you can stock up on filters

 

[Armando]

Bill can you believe I still have the cartridges of the last year group buy? I never had a chance to install them

 

[Aquadiva]

armando, increase your rejection rate.

Hmmmm...how do you do that?

-Linda

 

[Syris]

Bill can you believe I still have the cartridges of the last year group buy? I never had a chance to install them

Same here

I dont need to change filters often, matter of fact Iam still using the original color changing DI cartridge from 2yrs ago. My well water seems to be pretty clean, TDS is always ~120ppm

 

[paulpp187]

buckeyefieldsupply.com has some good prices on filter replacements

 

[Armando]

Nuno, I changed the way the meter is plugged in as you recommended.

It seems odd but I'm getting "pre-DI" TDS of 5 and "post DI" TDS of 5

 

[nunofs]

That means your DI resin is done, time to replace it

Nuno

 

[nunofs]

Humm, did you recalibrate the meter, or did it come down form the earlier 9ppm to 5ppm?

Anyway, assuming that your tap water is still around 148, your membrane efficiency is (148-5)/148*100=96%, which is excellent... no need to replace the membrane or any other cartridges, just replace the DI resin.

FWIW, I go through resin pretty quickly because the TDS of my tap water is around 250.

Nuno