When to replace RO membrane and DI resin?

[Oscarmk]

I have a barracuda 100gdp ro/di system, I think I have had it for about 20 months now, I have changed the prefilters a couple of times and also 4 months ago upgraded the system to have the chloramine blaster upgrade kit. However I have never changed the RO membrane nor the DI resin, the system continues to produce 0 TDS water, but for a month now I can see the DI resin is pretty much all used up, yet I am still getting 0 TDS.

I have bought the replacements already a long time ago, was wondering if one should wait till the system starts producing at least 1 TDS water before replacing the cartridges?, or if after a set amount of time one should just change them?.

Planning to just change both the DI and RO membrane at once. The system produced 5 gallons every week, and now 10 gallons every week past 11 months, so I guess that's why it has lasted so long.

 

[Opus]

You do not need to change both at the same time. The RO membrane should last from 3 to 5 or more years. The DI should be replaced once you start getting 1 tds reading. The membrane is more complicated. You need to know your tap water tds, the tds after the membrane and the efficiency rating of the membrane. Most are around 96% but some are 99%. Take the tds reading after the membrane and divide it by your tap tds and subtract that from 100. That is your actual efficiency rating and compare that to what your membrane is rated. If it is below the stated rating then you should look at replacing.

FYI, the chloramine kit is not needed. A good carbon block will break down chloramines.

 

[DFW]

I would be suspicious of the di resin after this length of time. I can't see it lasting this long under any conditions. If you use color changing resin, then start checking tds when color is all gone, you may find your meter is off, which is not unusual, I think. If you contact the manufacturer of your tds meter, they will explain how this works better than I can.

 

[Oscarmk]

Thank you both, I think the RO membrane I have is 99%, I'll check, about the chloramine blaster, I have read a good carbon block could be sufficient, but the kit allows you to have two, I guess it is safer just in case.

I never though about the TDS meter being off, but that could be true, I have a HM Digital EZ meter, they come pre-calibrated, it is supposed to be good enough, but maybe there are better options?. Anyway it does seem to work, I have seen readings of 1-5 ppm as well as 0, if I test the water before coming into contact with the mixing bucket it is zero, once it comes in contact it is usually 1 or 2, because of salt residue. I will change my DI resin, it is color changing I can't really see black anymore, it is all changed now, it has been very close to used up for about a month now, but since it kept readinf zero TDS I assumed it was fine. Tap water gives me 150-250 readings.

 

[Mike R]

You need catalytic activated carbon to remove chloramines. They will go right through a standard carbon block.

 

[Oscarmk]

@Mike R wrote:

I have also read this, some people do say a carbon is sufficient, but after a lot of online research I decided to get the upgrade kit, it comes with 2 catalytic activated carbon blocks. I actually didn't know about chloramines till the tank tour, and we went to your house and saw you have this monster chloramine block, after asking and doing research I ordered it shortly after.

 

[DFW]

After going through the ro/di filters, I have always added Prime to make sure that there are no problems. I add 1/10 ml per gallon ro/di water. I live in Fort Worth with chloramines, and have mostly always used regular carbon blocks.

 

[Opus]

Here is a link to The Colony's water report for 2015.

https://www.thecolonytx.gov/Depts/PublicWorks/Documents/2015WaterQualityReport.pdf

Bad part about The Colony is they have 3 sources for their water.

Your TDS meter is probably fine. If you really have a 99% rejection rate RO membrane then based on a 250 tds at the tap, your DI should be able to handle around 1400 gallons before it is exhausted. It doesn't hurt to change the DI media but I would wait until it it producing 1 tds before I would change it. Just because it has changed colors doesn't mean it is really used up. I've had mine change color and still go for months before my tds starts reading 1. Remember it is packed in their tight and you are only seeing the outside part. To be totally safe, you might take your tds meter with you the next time you go to the LFS and see if they will let you compare it to their meter just to make sure it is reading correctly.

 

[Mike R]

@Opus wrote:

All very excellent advice. [smilie=clapping.gif]

 

[Oscarmk]

@Opus wrote:

Thank you, this is perfect, I checked on the AquaFX website and I have a 98.6% RO membrane, I guess people round it to 99?. I'll take my TDS meter wkth me next time to compare just in case.