TDS???

DRC Archive General Saltwater Discussion
1

I have a pure flo II ro unit with the DI add-on. I have a T coming off the RO membrane before it goes to the DI unit to see how well the membrane is doing. I am wondering what TDS is acceptable coming out of the membrane. Should it be reading 0 coming out of the membrane? I am reading 8 TDS out of the membrane and obviously 0 TDS after the DI unit. Should i replace the membrane? I know the DI unit should take out what TDS is left but is 8 TDS acceptable or should i replace the membrane? Let me know your thoughts.

2

you need to do the math to see if it matches the rejection rate listed for the membrane

here is a form to figure it out.

http://www.spectrapure.com/CALC-FORMULA.pdf

3

Thanks! I will check it out!

4

Matt is your DI after the membrane?

You may wanna try and plumb it prior to the membrane and that should help save it little longer.

5

DI is after the membrane. Wouldn’t DI before the membrane be doing all the work? Just wondering? I was wondering if 8 TDS was going to exhause the DI cartridge faster than normal and if I should replace the membrane as the DI is just to polish what the membrane leaves behind. Just thinking out loud… Frank, is the math just for GPD?

6

The DI before the membrane is saving the $75-$100 membrane verses $10 of Di material but still depends on how bad your water is going in. 8 ppm of TDS is not real bad but not optimal when it comes the norm of what we wanna put in the tank.

I can usually go at least 6 to 8 months before changing DI material and then is never more then 3 ppm
The membrane last for well over a year.

But is all fairness the TDS going into my Ro have never seen higher the 40 ppms

7

sorry linked to the wrong thing
here is the section to enter your tap tds and your post RO tds and it will calculate the rejection rate for you

8

yeah matt, what frank said to calculate the rejection rate… 8 out of the membrane sounds just fine, and the di will have no problem polishing off that amount and still lasting a good while.

bill’s technique would work, but then why use the membrane at all? the di will take tap water to 0 all by itself, it would just exhaust quick and it aint cheap.

matt do you know the rejection rate of your membrane?

9

I’ve got my DI after the membrane…its just how BRS recommended it. I’ve got 11ppm going into my DI (which is coming right from the membrane). I have the kit to flush the membrane but haven’t installed it yet…guess I need to get on that…

10

Thanks! TDS is 110 going in and 8 coming out of the membrane for a 92% rejection before the DI. I think that is pretty good!

11

I get 7 TDS from my membrane, 0 after DI.

12

My membrane is the slacker of the bunch sofar! hah

13

92% is not very good and will be eating your DI a lot faster then you may want, if your DI life is OK with you then your fine, mine is three years old now and is down to 97.4% in 78 out 2 when it was new it was over 98%

My DI last me about 8 months

14

Showoff! ::thumbsup::

15

Here is a chart provided by Matt of BFS:

16

btw matt… what happened? i thought you were a tap water guy… u said RO was for sissys ::rofl::

17

Well I have used tap water in the past but i have had algae issues here and there so I started using ro/di as I should. According to that chart my di cartridge will last about 700 gallons at 8tds! Anyone know a good place to get replacement resin?

18

I bought a big bag from brs a while back… seems to be good quality… i have enough for you to pack a cartridge and try it out if you want or need some asap…lmk

19

[quote=“saltcreep, post:16, topic:6169”]
btw matt… what happened? i thought you were a tap water guy… u said RO was for sissys ::rofl::[/quote]

Delaware tap water hmmmm ::thinking::

http://www.delawareonline.com/article/20100725/HEALTH/7250305/Delaware-Drinking-Water-Risk-Filtering-strongly-recommended?fb_action_ids=10100836852412964&fb_action_types=og.recommends&fb_ref=artsharetop&fb_source=aggregation&fb_aggregation_id=288381481237582

20

I too purchase DI resin from BRS.