Changed RO filter, high TDS?

[Adequate]

I just replaced the pre-filter and carbon cartridges of my RO filter, and it's been flushing for hours and hours now. Tap water TDS is ~120ppm. Pre-flush, the TDS of the output water came out at around 70ppm, and slowly, it's been creeping down. However, the lowest it seems to go is 25ppm, and it doesn't seem to get any lower. I've opened up the cartridges to check that everything was in working order, from what I could tell, everything seemed fine.

What could be the issue? I changed the RO membrane less than a year ago and from what I've read, the RO membrane only needs replacing every two to three years? The last time I changed the cartridges (that time, I changed all three filters: sediment, carbon and RO membrane), the output water was 0ppm.

 

[WIReefer]

Are you getting proper water pressure threw unit? Also I change my filters at least once a year all of them.

 

[Yates273]

Did you change out Di resin also. If so just make sure you put canister back in the right way. A lot of people including myself put it in upside down once I flipped over it fixed my problem.

 

[Adequate]

Are you getting proper water pressure threw unit? Also I change my filters at least once a year all of them.

Oh yeah, thanks for reminding me, I forgot to mention. 80psi

Did you change out Di resin also. If so just make sure you put canister back in the right way. A lot of people including myself put it in upside down once I flipped over it fixed my problem.

I don't use DI, it's just RO. Where I'm from, reefers seem pretty content with just RO and don't usually go the extra mile for DI. I'm pretty happy with the 0ppm water that I get from RO, or at least, what I should be getting from RO. I might consider DI in the future though, couldn't hurt ‍.

 

[Reef.]

faulty filters
Inserted incorrectly
TDS meter faulty
If using a handheld TDS meter, the container could be contaminated
Wrappers still on the filters
O rings failed

 

[brian2kgt]

Did you disconnect the RO membrane before you did the flush? The carbon cartridges need flushed before you hook them up to the RO membrane, when new they can produce carbon dust that will foul it.

 

[Reef.]

Did you disconnect the RO membrane before you did the flush? The carbon cartridges need flushed before you hook them up to the RO membrane, when new they can produce carbon dust that will foul it.

Good,point, that’s quite important.

 

[stanlalee]

There is nothing that would have that bad a rejection rate besides a bad membrane. HOW it went bad is the only question. As mentioned did you flush your pre filters BEFORE the membrane? What's your incoming water pressure (unlikely the problem. It would should up with little water production).Does your source water have high chloramine levels (like > 1.0 ppm)? At 120 tds you have relatively high quality source water. Even a poor performing (low rejection rate) membrane should leave the membrane in single digits after a minute or two of operation.

 

[Adequate]

faulty filters
Inserted incorrectly
TDS meter faulty
If using a handheld TDS meter, the container could be contaminated
Wrappers still on the filters
O rings failed

All of these are possible, except the wrapper still being on the filters. Pretty sure I accounted for that

Did you disconnect the RO membrane before you did the flush? The carbon cartridges need flushed before you hook them up to the RO membrane, when new they can produce carbon dust that will foul it.

There is nothing that would have that bad a rejection rate besides a bad membrane. HOW it went bad is the only question. As mentioned did you flush your pre filters BEFORE the membrane? What's your incoming water pressure (unlikely the problem. It would should up with little water production).Does your source water have high chloramine levels (like > 1.0 ppm)? At 120 tds you have relatively high quality source water. Even a poor performing (low rejection rate) membrane should leave the membrane in single digits after a minute or two of operation.

I didn't know that had to be done? I didn't do it last time and I had no problems, but it might be the source of the issue this time. How would I check the health of the RO membrane?

No idea about incoming water pressure, only that the pressure gauge on the filter reads 80psi. My source water only contains chlorine, not chloramine.

 

[Reef.]

All of these are possible, except the wrapper still being on the filters. Pretty sure I accounted for that



I didn't know that had to be done? I didn't do it last time and I had no problems, but it might be the source of the issue this time. How would I check the health of the RO membrane?

No idea about incoming water pressure, only that the pressure gauge on the filter reads 80psi. My source water only contains chlorine, not chloramine.

look some people forget to remove the wrappings ok

 

[brian2kgt]

I didn't know that had to be done? I didn't do it last time and I had no problems, but it might be the source of the issue this time. How would I check the health of the RO membrane?

You may have just got lucky last time and had a carbon cartridge that didn't have much dust in it, some brands are better than others. I have seen new carbon blocks where the first water that flushes out is actually black. If this happened to you then you may have ruined the membrane.

The only way to check the health of an RO membrane is to take the TDS in and the TDS out and do the math to figure out the rejection rate and compare it to the membrane's specified rejection rate, this number is usually in the high 90's. Using your numbers of 120 in and 25 out puts you at a 79% rejection which is pretty bad and looks like it is probably shot unfortunately.

 

[Adequate]

You may of just got lucky last time and had a carbon cartridge that didn't have much dust in it, some brands are better than others. I have seen new carbon blocks where the first water that flushes out is actually black. If this happened to you then you may have ruined the membrane.

The only way to check the health of an RO membrane is to take the TDS in and the TDS out and do the math to figure out the rejection rate and compare it to the membrane's specified rejection rate, this number is usually in the high 90's. Using your numbers of 120 in and 25 out puts you at a 79% rejection which is pretty bad and looks like it is probably shot unfortunately.

Last time, I used Reef Pure's replacement cartridges, according to their website, the rejection rate for the membrane is 98%. If my maths is correct, the output water's TDS should be ~2.5ppm.

I didn't find any colour abnormalities upon flushing, looks exactly the way RO water should.

If it helps, the wastewater is coming out at ~180ppm. So it seems that some filtration is going on.

 

[Reef.]

Last time, I used Reef Pure's replacement cartridges, according to their website, the rejection rate for the membrane is 98%. If my maths is correct, the output water's TDS should be ~2.5ppm.

I didn't find any colour abnormalities upon flushing, looks exactly the way RO water should.

If it helps, the wastewater is coming out at ~180ppm. So it seems that some filtration is going on.

It would look normal as if there was any carbon dust the membrane will have blocked them but in doing so lost it’s effectiveness.

 

[Adequate]

Is there any way to reverse the damage to the membrane or should I just replace it altogether?

 

[Reef.]

Is there any way to reverse the damage to the membrane or should I just replace it altogether?

it’s a sealed unit, replace if you think that is the reason.

you could upgrade to a bigger membrane whilst you are at it to feel it is not all for nothing, not sure what membrane size you have but bigger ones normally fit in the same tube, just replace the flow restrictor at the same time, to the size of the new membrane.

 

[Adequate]

I just ordered a new membrane, hopefully it'll be arriving soon.

I'm guessing I still need to flush the membrane once it arrives?

 

[Reef.]

I just ordered a new membrane, hopefully it'll be arriving soon.

I'm guessing I still need to flush the membrane once it arrives?

Normally they have a food preservative on them so it’s recommended to flush for 1 hour and discard the water, check your instructions yours may be different.