Acceptable TDS for RO/DI

[BKD067]

I was wondering what is the highest TDS reading you are allowing before changing your filters on your RO/DI unit? I know 0 ppm is ideal but is it acceptable to allow it raise to slightly above 0 ppm without any adverse affects?

I have produced approximately 150 gallons with my current filters and the TDS has been at 0 ppm. I just made another 5 gallons and the TDS reading for the current filters is now reading 2 ppm.

Shouldn't I be getting more water production than 150 gallons before the TDS starts rising above 0 ppm? Could I be doing something wrong or is it the quality of the city water that I am filtering? Are there different qualities of filters on the market out there that I should be purchasing.

I purchased my 6 stage RO/DI unit from Filters Direct in Santa Ana and the replacement filters as well.

Any advice or help from experienced reefers would be greatly appreciated.

Thank you-Brian

 

[reef_doug]

Curious to what the TDS is after the membrane and before the DI. You could unscrew the section going into the DI chamber and fill a cup.

What is your source TDS?
How old is the unit (membrane)?
Yes, there are different quality prefilters and membranes.
Did you replace the DI filter also? How old is it?

I believe your city uses Chloramines, can anyone confirm for the city of Cypress?

 

[sync]

yes you should be getting more than 150 gallons I have purchased the same on from filter direct. Has your resign turned yellow yet? also are you using it for top off ? and do you have the 75GPD or 100GPD membrane?

 

[BKD067]

Hey guys-thanks for the response. The unit is a Water General RD-102 100gpd purchased from Filters Direct. The last filter change I replaced the qty 1-sediment filter qty 2-carbon filters and the DI resin in both DI resin chambers. I am only on my second set of filters and DI resin. I was told it would be a while before the membrane would need to be replaced.

The inlet water pressure(source) to the unit is operating anywhere between 60-80psig

I tested the tap water inlet to the unit and it was at 380 PPM TDS. I have seen it as high as 600-700 PPM on certain days.

The reading outlet a the membrane before the DI chambers was at 290 PPM TDS. The DI resin appears to be the dark brown/red color it has been. I does not look like it has turned yellow.

The final product is running about 2 PPM TDS

Is this unit acceptable for generating top off water and mixing my own salt solutions or should I purchase a better unit?? Any help/suggestions are greatly appreciated. Thanks guys and gals

 

[goth2o]

if it makes you feel any better just test the water from your lfs i just tested some and tds was 25 ppm

 

[reef_doug]

Your membrane is shot. A 95%-98% rejection should give you around 12-16 TDS output from the membrane before it hits the DI.

I would replace the membrane with a 90 GPD (around $40) and get a matching flow restrictor (<$5). The membrane should last a couple years provided it is protected from damage caused by chlorine & chloramines. It's best to replace carbon blocks every 4-6 months to protect the membranes.

BTW... Spectrapure has 98% rejection membranes on sale at the moment.
http://www.spectrapure.com/St_RC_Appreciation.htm

 

[Wes]

yeah, I agree... your membrane should be able to take out more than 1/4 of your TDS...

 

[lowbudget]

1 once it doesnt read zero i change out all the filters but i normally keep a membrane for about 2 yr tops

 

[sync]

BKD067

I had the 100gpd membrane at first and it did the same thing yours did I called filters direct and told him about the problem and he sold me a GE 75gpd at cost and I'm now getting 8 TDS out of the membrane and I usually have 450PPM going in. You can use it for top off as I do but you need to get the 5 gallon tank to help with the TDS creep.

 

[BKD067]

Thanks everybody for your input and advice. Just ordered what I needed from Bulk Reef Supply.

 

[five.five-six]

in my area, on a good day we have 550ppm, on a bad day, closer to 800, I was going through DI fasssst, I now use a 2nd DI chamber, and rotate the oldest cartage out, the newer one to buffer the brand new DI (does this make sense) any way i now get 500+ gallons per cartridge, before it was about 100