RODI Questions (1-year in):

[cybrook1421]

Hello! I am getting higher TDS after the membrane than I am used to, and am trying to figure out if it is time to replace the membranes. I have not replaced them yet since I got the filter. I have a BRS 6-stage 150GPD that has been used regularly since June of 2022 (and in April to fill the tank originally). I have a booster pump and autoflush system installed for that entire time as well.

From my memory, the second to last time I ran it, the TDS before the DI resin was 8-9. This was the usual amount I would get. The last time was around 12. Today it is 25. Outgoing TDS after DI is still 0, but I imagine I am burning through the DI with a TDS of 25. I make around 25 gallons at a time.

Incoming TDS is usually around 250-320 depending on the day. PSI is set at 70-75, and there is seemingly no PSI difference between before the sediment filter and after the carbon filter, so I know those don't need changed yet.

I have changed the sediment filter once (Nov. 2022), the carbon filters once (Nov 2022, rotated the second one to the first spot and then replaced the other), and the DI once (April 2023, again rotated the second one up and replaced the other).

Is it time for the membranes or is there anything else I should try before doing so? Have I been doing ok on the maintenance/timing of replacing the other filters so far?

Bonus question: should I be manually flushing the membranes every so often, as well as keeping the autoflush on there?

Any help is much appreciated!!!

 

[Uncle99]

This is exactly what mine does when membrane, carbon and sediment need changing. 10-20-35 comes quickly.
Time to change.

I’ve never flushed mine. Maybe I should???

Membranes for me last 15-24 months at 20g per week.
I just replace.

 

[Freenow54]

Hello! I am getting higher TDS after the membrane than I am used to, and am trying to figure out if it is time to replace the membranes. I have not replaced them yet since I got the filter. I have a BRS 6-stage 150GPD that has been used regularly since June of 2022 (and in April to fill the tank originally). I have a booster pump and autoflush system installed for that entire time as well.

From my memory, the second to last time I ran it, the TDS before the DI resin was 8-9. This was the usual amount I would get. The last time was around 12. Today it is 25. Outgoing TDS after DI is still 0, but I imagine I am burning through the DI with a TDS of 25. I make around 25 gallons at a time.

Incoming TDS is usually around 250-320 depending on the day. PSI is set at 70-75, and there is seemingly no PSI difference between before the sediment filter and after the carbon filter, so I know those don't need changed yet.

I have changed the sediment filter once (Nov. 2022), the carbon filters once (Nov 2022, rotated the second one to the first spot and then replaced the other), and the DI once (April 2023, again rotated the second one up and replaced the other).

Is it time for the membranes or is there anything else I should try before doing so? Have I been doing ok on the maintenance/timing of replacing the other filters so far?

Bonus question: should I be manually flushing the membranes every so often, as well as keeping the autoflush on there?

Any help is much appreciated!!!

I do mine entirely every year including the DI resin. Sometimes sooner No problems

 

[Woodyman]

Sounds like it, time for a membrane swap.

Keep this in mind for your DI consumption.

Ignore the branding for spectrapure. The concept still applies. For example sample of you were typically around 8-9 let's round that up to 10 and call it a 98% rejection, if your at 20+ now your below 96% so you'd be using significantly more DI than normally. The numbers below will vary based on your actual water, but the same concept applies, just plug in your numbers.

Also if your not monitoring already it's a quick way to gauge when your seeing your numbers drop off so you can preemptively prepare replacements as needed.

RO/DI Basic Guide

There are always a lot of questions regarding which RO/DI setup do I need, how many stages, how do I know when to change filters/membranes, I’m getting a weird TDS value, etc. Hopefully this clarifies a few things and helps some of you out one day. My first recommendation would be to find the...

www.reef2reef.com

 

[Buckeye Hydro]

Fun fact to know and tell: All Filmtec 75's are factory spec'ed at 99% rejection.

 

[cybrook1421]

Fun fact to know and tell: All Filmtec 75's are factory spec'ed at 99% rejection.

I bought two new membranes last week, and after installing, re-installing, re-installing again, then testing and more testing, the new membranes didn't do anything! I am still at about 27TDS after the membrane. Today's tap TDS was about 330. I installed them on Thursday last week, let them run to get rid of the preservative, and then waited over 24hours until today to test again. So why am I not getting this 99% rate? I am running dual 75 membranes with a 550 flow restrictor and 75-80 PSI into the membranes. I also bought and installed all new sediment and carbon filters too. I don't understand this difference when two months ago I was getting 6-10 TDS after the membrane with older sediment and carbon filters.

 

[Buckeye Hydro]

I bought two new membranes last week, and after installing, re-installing, re-installing again, then testing and more testing, the new membranes didn't do anything! I am still at about 27TDS after the membrane. Today's tap TDS was about 330. I installed them on Thursday last week, let them run to get rid of the preservative, and then waited over 24hours until today to test again. So why am I not getting this 99% rate? I am running dual 75 membranes with a 550 flow restrictor and 75-80 PSI into the membranes. I also bought and installed all new sediment and carbon filters too. I don't understand this difference when two months ago I was getting 6-10 TDS after the membrane with older sediment and carbon filters.

Well:
1. You shouldn't be running two membranes in series if you have hard water. The feedwater to the second membrane is going to be well over 330 ppm TDS.
2. You're using a flow restrictor intended for a 50 gpd membrane with 150 gpd worth of membrane. Remember that the factory spec on Filmtec membranes calls for a 5.5:1 waste to permeate ratio.
3. What membranes did you buy and install. Why are you replacing membranes after just one year? Hint: You have hard water and are running 2 membranes in series with the wrong flow restrictor.

There are other potential issues, but I'd start there.

 

[Freenow54]

I bought two new membranes last week, and after installing, re-installing, re-installing again, then testing and more testing, the new membranes didn't do anything! I am still at about 27TDS after the membrane. Today's tap TDS was about 330. I installed them on Thursday last week, let them run to get rid of the preservative, and then waited over 24hours until today to test again. So why am I not getting this 99% rate? I am running dual 75 membranes with a 550 flow restrictor and 75-80 PSI into the membranes. I also bought and installed all new sediment and carbon filters too. I don't understand this difference when two months ago I was getting 6-10 TDS after the membrane with older sediment and carbon filters.

I know this may be a silly question but was everything hooked up properly again? I just changed mine, and realized how easily it could be done. IE bypassing some of the filters, and or backflow