RO/DI Help!

[newreefer92]

Hey All,

I wanted to reach out as I have been having some issues with TDS being around the 18-19 range before going into the resin cartridge. My specific setup up is the BRS 4-Stage system with the 150 gal per day upgrade. So a sediment filter, 1 um carbon block, 2 75 gallon per day RO membranes and then a single bed color changing DI resin. The 18-19 range was measured about 4 hours after I replaced both RO membranes. The Carbon block and sediment filter have not been changed in a while and wanted your opinions. Will changing out the carbon block and the sediment filter bring that down significantly before the resin cartridge or do I need some additional filtering beyond what I have along with replacing the CB and Sediment filter.

Thank you all for your time!

 

[ryeguyy84]

Was the tds after the membrane lower before you replaced the membrane?

What's your water pressure?

Sent from my SM-G950U using Tapatalk

 

[newreefer92]

No it was slightly higher that is why I replaced them! Pressure is around 90 PSI.

 

[mcgyvr]

What is your source water TDS?
If your source water TDS is high 18 might be normal.


And no..
Sediment/Carbon blocks do not reduce TDS

 

[alton]

Like mcgyvr said if you tds coming is around 600, 18 would be normal. 600 x 3% = 18 tds. Also if you have chloramines or high chlorine levels 1 carbon block will not last very long. You can check it by buying chlorine testing strips from amazon that check chlorine and free chlorine before your water enters your membrane. If not chlorine will eat through your membrane fairly quickly. I tried the dual membrane once and went back to the single membrane filling up a 60 gallon barrel to keep on hand.

 

[newreefer92]

My tds from the tap is around 375 to 400 so maybe you are right that that would be the norm!

So what would you recommend instead/in addition to the 1 um carbon block, that really is the basis is what I am wanting to know. What has worked good for you guys?

 

[mcgyvr]

Did you buy a quality RO membrane?

400TDS with a 97% rejection ratio membrane should net you 12 TDS at the inlet to the DI stage.. If that is running around 95% then you are at 20 TDS.. So yes.. Seems "normal"..

400TDS with a 99% rejection ratio membrane should net you 4 TDS at the inlet to the DI stage..

If you want to reduce TDS into the DI stage then one solution is a better (higher rejection ratio) RO membrane..

 

[newreefer92]

I am running two Dow 75 gallon per day RO membranes.

 

[mcgyvr]

Assuming you have the BW60-1812-75 its a "typical" 99% but minimum 96% rated membrane..
Thats with a test source water of 250ppm TDS @ 50PSI min at the membrane inlet..

So what you are seeing is likely "normal"..

Have you measured water pressure at the inlet?

Old prefilters will certainly reduce membrane inlet pressure..

At this point I would certainly replace your prefilters and check your pre RO membrane pressure.. I suspect that will help to reduce the pressure drop which will likely improve pressure a the membrane thus potentially improving your rejection rate..
Then if pressure is too low we can instruct on the ways to improve that to help there.. (increase water pressure regulator or booster pump,etc...)

 

[newreefer92]

Psi going into the ro membrane is 90, is that not enough? All prefilters have been replaced!

 

[mcgyvr]

Psi going into the ro membrane is 90, is that not enough? All prefilters have been replaced!

90PSI is plenty (excessive IMO)..
Now that your prefilters have been replaced has your TDS gone down some?
If not what you are getting is what you will get with those membranes..

Only thing you can really try is to reseat them again to make sure nothing is blowing by.. but beyond that it is what it is..

 

[JustAClownFish]

DIY a return line and have the filtered water run through one more time. Or put two RO/DI units in a row. You will have 0 tds.

 

[newreefer92]

90PSI is plenty (excessive IMO)..
Now that your prefilters have been replaced has your TDS gone down some?
If not what you are getting is what you will get with those membranes..

Only thing you can really try is to reseat them again to make sure nothing is blowing by.. but beyond that it is what it is..

TDS did not go down but for some odd reason I noticed that the di resin is lasting longer. Super odd!