What steps should I take to lower my TDS?

[chiroboy126]

Hi all,

I’m wondering what steps anyone would recommend for lowering my TDS. I use a handheld TDS meter. My tap water is reading 141 ppm, the RO/DI unit is reading 69 ppm. I replaced the pre-filter & DI resin last month and have only needed to make water twice since then. I have a 100gpd membrane on there now and it was replaced probably 3-4 months ago.

My initial thought is that I need to replace the membrane, but should I buy a 50-75 gpd as I usually only make around 40 gallons at a time?

My DI resin changes colors when it’s exhausted and it hasn’t started to change yet but I’m trying to get as close to 0 as possible and realize the resin could be the culprit too. Any suggestions would help.

 

[208reef]

Test the TDS of the waste water line. If your tap water is 141ppm and RO/DI is only bringing you down to 69ppm, either you have the waste/product line mixed up or something isn't connected up properly. What brand/model RO/DI unit do you have?

 

[chiroboy126]

Test the TDS of the waste water line. If your tap water is 141ppm and RO/DI is only bringing you down to 69ppm, either you have the waste/product line mixed up or something isn't connected up properly. What brand/model RO/DI unit do you have?

Waste water shows 186ppm TDS. I’m using a Aquafx barracuda RO/DI unit

 

[KrisReef]

Sounds like the membrane is not properly installed and/ or is defective.

95% rejection should produce ~ 5tds, before the resins

 

[chiroboy126]

Sounds like the membrane is not properly installed and/ or is defective.

95% rejection should produce ~ 5tds, before the resins

I ordered a new membrane and will test after installing. I wanted to make sure the likely culprit was my DI resin or something else before buying another membrane.

 

[Sumbub]

Did you ever flush all the carbon blocks and membrane when you first installed? And did you flush again before making the 2 water changes?

 

[chiroboy126]

Did you ever flush all the carbon blocks and membrane when you first installed? And did you flush again before making the 2 water changes?

I did flush. I did not test TDS before changing the carbon block last time however.

 

[Tamberav]

I ordered a new membrane and will test after installing. I wanted to make sure the likely culprit was my DI resin or something else before buying another membrane.

To know if it’s the membrane, you test tds of tap then TDS of RO before it goes to the DI. Then calculate the rejection rate.

 

[Buckeye Hydro Verified Sponsor]

Try a filmtec membrane. Always run the system for at least 90 seconds (if you have a single membrane) before you measure the TDS of your permeate (RO water) or DI water.

 

[chiroboy126]

I ended up needing a new flow restrictor on my RO/DI unit. After I installed that and reinstalled my membrane my TDS is now at 0. Thanks everyone for all the help. I learned a lot!