RO/DI - TDS issues

[poplalud]

Hey all! I set up my new AquaticLife 5 Stage RO/DI filter yesterday, flushed it, ran it for about 30min, dumped the water and started a new "real batch" today as I impatiently await my UNS R75 to ship. It looks like I'm getting about 50psi on the gauge, but after about an hour of running it today, I collected a sample and tested TDS. I'm at ~80ppm (@76deg) which is alarming. I tested my tap water and got ~430ppm (@74deg) which is incredibly alarming. The current setup isnt ideal and I think I can get another 10psi if I shorten the run from my spigot to the filter (will this help?), but looking for any other suggestions that will help me get to TDS 0. Thanks!!

 

[sjfishguy]

You are getting 80 after the DI? If so you are doing something wrong

 

[JumboShrimp]

I am not familiar with that particular system, and which components you have, but just guessing, I bet a booster pump would raise you to an operating level of 70-80psi. (I have the booster pump from Bulk Reef Supply.) If I'm way off, someone please correct me. I don't want to risk giving bad advice.

 

[kboogie]

The TDS numbers you are seeing suggest multiple stages, either need the media replaced, or you are experiencing creep from a bad seal. I'm making the assumption that your testing process is valid.

When was the last time you changed your media?

How old is your membrane?

If you are getting chlorine at your membrane, then that will cause it to deteriorate and allow for TDS creep. Additionally, if your membrane is not properly seated that will cause major creep. Your membrane should reject 92% to 99% of the TDS when run at proper pressure and the membrane is not damaged by chlorine. That means you would see about 34 TDS going into the DI stage on the high and less 8 TDS going into the DI stage if all is running well.

Increasing your pressure using a booster pump will improve your rejection rate if you have a membrane that is not damaged. If your membrane is damaged then increasing pressure will increase the TDS creep.

If you haven't changed your media (carbon block, sediment filter, and DI resin) in a while, I recommend doing that. Your high input TDS is going to result in higher DI resin consumption in general.

 

[poplalud]

The TDS numbers you are seeing suggest multiple stages, either need the media replaced, or you are experiencing creep from a bad seal. I'm making the assumption that your testing process is valid.

When was the last time you changed your media?

How old is your membrane?

If you are getting chlorine at your membrane, then that will cause it to deteriorate and allow for TDS creep. Additionally, if your membrane is not properly seated that will cause major creep. Your membrane should reject 92% to 99% of the TDS when run at proper pressure and the membrane is not damaged by chlorine. That means you would see about 34 TDS going into the DI stage on the high and less 8 TDS going into the DI stage if all is running well.

Increasing your pressure using a booster pump will improve your rejection rate if you have a membrane that is not damaged. If your membrane is damaged then increasing pressure will increase the TDS creep.

If you haven't changed your media (carbon block, sediment filter, and DI resin) in a while, I recommend doing that. Your high input TDS is going to result in higher DI resin consumption in general.

System, membranes, and filters are all brand new, (arrived on Saturday). I'm assuming they are properly seated but I guess I'll tear it apart when I've got an hour or so. I was really happy with the packaging of the system (reminded me of how well Dyson packages their products and all items were in good shape) so i wasn't worried about damage to any components. I lubed all of the o-rings up with the supplied silicone (?) but I'm new at the whole RO/DI aspect of things so I'll rip it apart and see what I find. Thanks for the tips!

Guessing the water I'm getting at 80ppm cant be used to cycle dry rock?

 

[kboogie]

System, membranes, and filters are all brand new, (arrived on Saturday). I'm assuming they are properly seated but I guess I'll tear it apart when I've got an hour or so. I was really happy with the packaging of the system (reminded me of how well Dyson packages their products and all items were in good shape) so i wasn't worried about damage to any components. I lubed all of the o-rings up with the supplied silicone (?) but I'm new at the whole RO/DI aspect of things so I'll rip it apart and see what I find. Thanks for the tips!

Guessing the water I'm getting at 80ppm cant be used to cycle dry rock?

Can you post a picture of your unit? I did some research and it looks like you might have dual membranes and no DI stage. It also shows you might have 200GPD membranes which makes the pressure very important. I run a dual 200GPD membrane setup. I have a booster pump and my static pressure is between 72 and 78, my operating pressure is 66 to 72. If you are using 200GPD membranes, I personally would not use those with anything less than 60PSI of operating pressure.

I also thought of something else to check. You want to make sure your flush value is off. If you have your flush value open that will increase the TDS of your product/output water.

 

[Pntbll687]

You definitely need to flush, and purge the system for longer, specially if it's brand new.

When I replace a membrane, I make about 40 gallons of "good" water to ensure the membrane is good. I discard this water then make some more and test the tds.

You should be getting somewhere in the 95%+ rejection rate from before the membrane to after. So if there is 430 going into the membrane, I would want something in the 20-25tds directly after the membrane and before the DI. Pressure will play a big role in this and how well the membrane functions. You may want to look at getting a booster pump. Personally, I use the smart buddie booster pump from aquatic life.

 

[KStatefan]

Hey all! I set up my new AquaticLife 5 Stage RO/DI filter yesterday, flushed it, ran it for about 30min, dumped the water and started a new "real batch" today as I impatiently await my UNS R75 to ship. It looks like I'm getting about 50psi on the gauge, but after about an hour of running it today, I collected a sample and tested TDS. I'm at ~80ppm (@76deg) which is alarming. I tested my tap water and got ~430ppm (@74deg) which is incredibly alarming. The current setup isnt ideal and I think I can get another 10psi if I shorten the run from my spigot to the filter (will this help?), but looking for any other suggestions that will help me get to TDS 0. Thanks!!

Something is not correct if you are only getting 80 tds after running for 30 minutes. Call Aquaticlife for support since it is brand new.

Your source water being 430 is not alarming mine is 400 and not that uncommon

I doubt you will be able to get another 10 psi unless you have a very long run.

 

[poplalud]

Can you post a picture of your unit? I did some research and it looks like you might have dual membranes and no DI stage. It also shows you might have 200GPD membranes which makes the pressure very important. I run a dual 200GPD membrane setup. I have a booster pump and my static pressure is between 72 and 78, my operating pressure is 66 to 72. If you are using 200GPD membranes, I personally would not use those with anything less than 60PSI of operating pressure.

I also thought of something else to check. You want to make sure your flush value is off. If you have your flush value open that will increase the TDS of your product/output water.

Thanks for the info. You are correct. 5 stage 200gpd, dual membrane. I moved the system and have a much shorter run from the spigot to the filter. Looks like the move got me to just under 60psi. I flushed the filters/bypassed the membranes and looks like I’m still getting about 75-80ppm. I guess I’ll tear it apart, check seals/seating, filter/membrane damage and run it again. I’m guessing I’ve got about 4 hours total run through it which I’ll assume is about 12-15 hours of filtered water out of it. Guessing 5x that in waste.

 

[poplalud]

You definitely need to flush, and purge the system for longer, specially if it's brand new.

When I replace a membrane, I make about 40 gallons of "good" water to ensure the membrane is good. I discard this water then make some more and test the tds.

You should be getting somewhere in the 95%+ rejection rate from before the membrane to after. So if there is 430 going into the membrane, I would want something in the 20-25tds directly after the membrane and before the DI. Pressure will play a big role in this and how well the membrane functions. You may want to look at getting a booster pump. Personally, I use the smart buddie booster pump from aquatic life.

Can you explain the rejection rate? Also, I tore it apart, looking at the o-rings, filters, membranes all looked good and no signs of pinching/distress. Running water through it again and pegged at 60psi, 70ppm. Gonna let this thing run for a bit, calculate gph and hope a solid flushing will get me there while I look at booster pumps. Do I have to worry about too much pressure/regulator only needing a gain of 20psi?

 

[Shirak]

There is no DI stage on that model.

Your RO TDS should be better than 80ppm though. What are you using to measure?

 

[poplalud]

There is no DI stage on that model.

Your RO TDS should be better than 80ppm though. What are you using to measure?

Well I'll be dammed... Checks out! Lol. I'm using a cheap amazon TDS meter. I was thinking about going to a water fill up station to collect a small sample of their RI/DO to see what the meter shows against their water.

 

[Shirak]

Well I'll be dammed... Checks out! Lol. I'm using a cheap amazon TDS meter. I was thinking about going to a water fill up station to collect a small sample of their RI/DO to see what the meter shows against their water.

You can get the standard filter canisters and just run the RO to some DI. Single mixed bed or if you want to go with multiple cartridges you could go separate cation/anion and then you get better use out of your resin. BRS makes a variety of single, double, and a triple series

Doesn't explain the RO tds though and you need to figure that out first. 80ppm into your DI will eat up your resin fast. Could be the meter but I suspect not.

 

[Shirak]

Other option is you change one of the 3 canisters to a DI. You have 2 carbon filters currently and probably unnecessary if you have a high quality carbon block right after the sediment filter. Depending on the hook ups you might need to redo the tubing if you choose to change one to DI so it's getting water from the RO membranes. You would need either a prepacked DI canister or an empty one and some bulk color changing mixed bed DI resin. You would also need to use the clear housing on the DI section. It's currently on the sediment filter. Or you could just monitor tds of the DI output and change the mixed bed when it starts to read 1-2ppm

Lots of options on the DI. Still really puzzled why it's reading so much TDS on the RO. Let it run for a few hours. Do you have a LFS that might have a tds meter to check your sample?

 

[kboogie]

Other option is you change one of the 3 canisters to a DI. You have 2 carbon filters currently and probably unnecessary if you have a high quality carbon block right after the sediment filter. Depending on the hook ups you might need to redo the tubing if you choose to change one to DI so it's getting water from the RO membranes. You would need either a prepacked DI canister or an empty one and some bulk color changing mixed bed DI resin. You would also need to use the clear housing on the DI section. It's currently on the sediment filter. Or you could just monitor tds of the DI output and change the mixed bed when it starts to read 1-2ppm

Lots of options on the DI. Still really puzzled why it's reading so much TDS on the RO. Let it run for a few hours. Do you have a LFS that might have a tds meter to check your sample?

I understand the thinking, but I would not recommend that approach. This approach ignores the core problem of the TDS coming out of the membrane. If we assume the numbers are remotely in the right ballpark, there is a problem upstream that the DI will mask but not address. Once we address the TDS creep, adding DI becomes the priority.

 

[Pntbll687]

Can you explain the rejection rate? Also, I tore it apart, looking at the o-rings, filters, membranes all looked good and no signs of pinching/distress. Running water through it again and pegged at 60psi, 70ppm. Gonna let this thing run for a bit, calculate gph and hope a solid flushing will get me there while I look at booster pumps. Do I have to worry about too much pressure/regulator only needing a gain of 20psi?

60psi should be good, but depending on the tds you may want to invest in a booster pump

Rejection rate would be TDS coming out of the membrane divided by the tds going into the membrane. I want to see this number somewhere in the .01 to .05 range. In your case it is 80/430 = .18, the rejection rate would be 82% in this case, which in the world of RO units and membranes would not be good. You should be looking at about 25tds coming out of the membrane, this would put you in the 95% range.

Pressure is the key in RO units, especially when starting tds is high. The water is forced through the membrane where the dissolved solids can be removed, with lower pressure, water can find a "channel" around the membrane without passing through it, or only through a couple layers and then out, which adds to the tds on the output side.

 

[kboogie]

Thanks for the info. You are correct. 5 stage 200gpd, dual membrane. I moved the system and have a much shorter run from the spigot to the filter. Looks like the move got me to just under 60psi. I flushed the filters/bypassed the membranes and looks like I’m still getting about 75-80ppm. I guess I’ll tear it apart, check seals/seating, filter/membrane damage and run it again. I’m guessing I’ve got about 4 hours total run through it which I’ll assume is about 12-15 hours of filtered water out of it. Guessing 5x that in waste.

Thank you for posting the pictures. As you can see from the additional comments, there seems to be an issue with the membrane. Is it safe to assume the kit came fully assembled, and you just added the media and membranes? I ask because I want to make sure the concentrate/reject water line and flush lines were not crossed.

Did you have to flush the carbon blocks when you set it up?


I highly recommend getting a good inline TDS meter. This is one of the two I use.

HM Digital DM-1 TDS Meter

I use two TDS meters. One that monitors input into the system and output of the membrane, and the second that monitors input into the DI and output from the DI. It is very helpful in understanding how the system is performing.

I want to make sure you focus on addressing the TDS creep and the membrane, then we can worry about adding a DI stage, which will be highly recommended for aquarium use of your product water.


Are you in Texas or on well water? Your input TDS is very high in general. I'm in South Florida, where we famously have terrible water, and my tap water is 174 TDS. I usually only see tap water numbers as high as yours in Texas or when people are on a well. That is important because you might need carbon blocks specific to your water chemistry. I, for example have carbon blocks specifically for chloramine and heavy metals, which are present in our water.

 

[Shirak]

I understand the thinking, but I would not recommend that approach. This approach ignores the core problem of the TDS coming out of the membrane. If we assume the numbers are remotely in the right ballpark, there is a problem upstream that the DI will mask but not address. Once we address the TDS creep, adding DI becomes the priority.

Not it doesn't ignore the core problem. It's a separate issue. As I stated the RO tds needs to be solved before hooking up DI but the DI issue needs to be addressed as well since there is currently no DI.

 

[kboogie]

Not it doesn't ignore the core problem. It's a separate issue. As I stated the RO tds needs to be solved before hooking up DI but the DI issue needs to be addressed as well since there is currently no DI.

We are saying the same thing.

 

[Shirak]

We are saying the same thing.

Yes we are! :)