30 TDS Need some input

Ok friends. My RO/DI unit is 1.5 years old. It is a Coralife Pure Flo II RO/DI 50 GPD unit. I have replaced the 1 Micron filter and the Carbon block once back in December. The DI canister and the TFC membrane are the ones that came with the unit and I believe are still good. I checked my TDS today and they were 28-30. I ordered a new .5 micron filter and a new carbon block from SpectraPure today figuring I will recheck my TDS when I get the new stuff installed. My question is should I have spent the extra money and bought a new TFC membrane and DI cartridge? or is 30 still low enough to only need to change the pieces I changed? Maybe AZ Desert Rat will jump in here, I need advice Thanks in advance.

 

So after a little research it looks like any TDS and the DI canister is shot. Anybody Confirm?
Bump

 

Prefilters and carbons have very little to absolutely nothing to do with final TDS, their job is to protect the RO membrane from TSS or suspended solids (sand, silt etc) and chlorine. Its the job of the RO membrane and the DI resin to remove the TDS or dissolved solids.
You need three TDS readings to trouble shoot the system, tap water TDS, RO only TDS and final or RO/DI TDS. Since the membrane does 90-98% of the work its important to know how well it is performing. You can keep replacing DI resin but it may just be a crutch propping up a poorly performing RO membrane and you will soon have more invested in resin than what a new membrane would cost.

Get the three TDS readings along with your water pressure, water temperature and your exact waste ratio. This can be done with a measuring cup and a watch or clock. Time the flow for one minute from both the good and the waste lines and see if its about 4:1 or four times as much waste as the good. Many RO vendors use non adjustable flow restrictors and truthfully they are not a one size fits all device. Your pressure, temperature and TDS all have an effect on the amount of waste. This is why Spectrapure uses capillary tube flow restrictors which you trim yourself for your exact conditions.

I would say at a minimum you do need a new DI cartridge but check the RO only TDS before buying it as you may need a membrane and flow restrictor too if you have not had a high enough waste ratio and the membarne has fouled with solids causing the DI to fail. You can't go wrong with Spectrapures SilicaBuster DI resin, its custom blended fresh in their own facility, no prepackaged off the shelf stuff.

 

Yeah, you probably need new DI resin for sure. Also have you flushed the membrane? Is the DI a horizontal canister or is it vertical? I find that using a good vertical DI canister performs better than the horizontal ones. I use this with their resin and it works great!

Single DI Canister - English

My TDs read, 216 from tap, 12 after my membrane and 0 after the DI

 

Membrane flush kits have no proven value other than lightening your wallet. Keep your waste ratio at 4:1 and 99.9% of the time that is sufficient flushing.

Vertical DI canisters are much better as nctinter pointed out since they provide a bottom up flow pattern so all resin andwater come into contact with each other. Horizontals short circuit or channel so perform poorly, no good reef quality system uses a horizontal DI.

 

For whats its worth I have the same unit and am replacing my membrane after a year and a half found them cheap $38 at filtersfast.com and if you spend $100 ( I got four prefilters, two carbon filters, one RO membrane, and a new filter for my fridge for $102) its FREE shipping

 

You can get a 90 GPD treated and batch tested 98+% rejection rate membrane from Spectrapure for $30, can't go wrong with that since no one else tests or treats their membranes for improved efficiency. You already bought he best prefilter you can get with the 0.5 micron absolute rated prefilter and hopefully you went with the 0.5 micron 20,000 gallon carbon block too.
SpectraPure Customer Appreciation SALE! 20% - 50% off

 

Wish I knew about this last week. Oh well I needed a filter for the fridge anyway

 

Thanks for all the info guys! I appreciate the help AZDesertRat! My water pressure is 57psi @69 degrees. TDS out of tap are 278 and after the RO 42 and after DI it is 32. I am checking the rejection rate but I am pretty sure after the info you gave me I need to replace the TFC membrane and the DI resin. Thanks I will be back in a few

 

OK so this is interesting... my water is coming out 1 cup per minute and the rejection is barely over 1 cup per minute. Any ideas? TFC membrane is shot?