New RO system - high TDS: 240 tap > 19 RO

[Muffin87]

I got a new RO system.

1. 5 micron sediment filter
2. 1 micron sediment filter
3. 5 micron sintered carbon block filter
4. 100 GPD Dow Filmtec RO membrane (96-7% rejection rate)

The RO system is attached to a separate dual DI canister with mixed bed resins.

 

The RO gives weirdly high TDS water:

• Tap water 234-40 TDS
• After RO, 19 TDS. Rejection rate 92%!!
• After DI, 0 TDS

I double checked the readings by using two HM DM-1 In-Line Dual TDS Monitors.

 

I checked the sediment/carbon filters: the inner cylinder of all three filters is properly fixed in place at the bottom of the canister.

I use a booster pump, pressure is 50-60 PSI. The pressure gauge needle goes back and forth quickly, so it's difficult to tell the exact value.

 

Anybody knows what could be going on?

My tap water doesn't have chloramines, only chlorine dioxide. So having just one carbon block shouldn't be the issue?

 

Is 19 TDS acceptable for RO or is it going to burn my DI quickly?

 

Thanks a lot!

[Clown79]

Well during the winter my tds is 520, i have no idea what it is before di because my tds meter is a dual so in and out.

 

My tds comes out 0.

 

My filters all last 4 mnths

 

0.5 to 1 sediment (the larger the number the more particles get through creating more work for the carbon block.

 

Carbon block

Chloramine carbon block

Membrane

Di

 

My psi is 55-60.

 

Your water may just have high tds levels. Hard water can also cause higher levels.

 

 

 

 

[Christopher Marks]

1 hour ago, Muffin87 said:

Is 19 TDS acceptable for RO or is it going to burn my DI quickly?

Based on your incoming tap water TDS, that does seem high. Since it's a new system, it may be worth contacting the manufacturer for troubleshooting, and to ensure everything is operating normally. At 19 your DI resin will indeed run out faster, I think you should be seeing better results from a new unit. How many gallons have you produced with it so far?

[Muffin87]

Thanks everyone!

I did several experiments.

 

Today my tap water was 270 TDS.

 

The new system produces 18-20 TDS without DI.

My old system with its original membrane produces 4-6 TDS water without DI.

 

I then tried connecting the new membrane that came with the new RO system to my old RO system, and TDS went up, 18-20 TDS.

Then I tried connecting the old membrane to the my new system, and the TDS was just 4-6!! As you would expect! 98% rejection rate!

 

At this point it sounds like it's faulty membrane?

[Christopher Marks]

On 1/31/2019 at 6:28 PM, Muffin87 said:

Thanks everyone!

I did several experiments.

 

Today my tap water was 270 TDS.

 

The new system produces 18-20 TDS without DI.

My old system with its original membrane produces 4-6 TDS water without DI.

 

I then tried connecting the new membrane that came with the new RO system to my old RO system, and TDS went up, 18-20 TDS.

Then I tried connecting the old membrane to the my new system, and the TDS was just 4-6!! As you would expect! 98% rejection rate!

 

At this point it sounds like it's faulty membrane?

Have you run water through the system for at least 24 hours at this point? That should be enough time to purge any contamination from new filters. Are all the rubber seals on the new membrane in tact and seating properly?

 

You've done some good troubleshooting so far, are you able to contact the manufacturer for a warranty exchange? It happens sometimes.

[Muffin87]

On 2/4/2019 at 6:09 AM, Christopher Marks said:

are you able to contact the manufacturer for a warranty exchange? It happens sometimes.

I contacted the manufacturer.

He replied with a long email and claims that, since my tap water has 240-70 TDS, it's normal a 100 GPD high rejection dow filmtec membrane produces 18-21 TDS

He claims the 98% rejection rate is only true of lab tests, and 92-3% rejection is acceptable.

 

To me, that sounds like a load of BS to be perfectly honest.

Plenty of people use 100 GPD high rejection dow filmtec membranes, and it'd seem strange if they were all happy with such low rejection rates.

I'm sorta tempted to get an identical membrane and see if I get the same results.

 

On 2/4/2019 at 6:09 AM, Christopher Marks said:

Are all the rubber seals on the new membrane in tact and seating properly?

As far as I can tell, there are no rubber seals and the membrane is seating properly. Where would you expect to find rubber seals?

 

On 2/4/2019 at 6:09 AM, Christopher Marks said:

Have you run water through the system for at least 24 hours at this point?

I have, and it's stable at 18 TDS now.

 

Thanks for the help everyone!

Let me know your thoughts!

Thanks everyone!