View Full Version : Troubleshooting Help: Fast Resin Depletion

05/14/2010, 09:18 PM
First, off thank you Jim for all the great service in the past. This is the only place I buy my resins. I've researched this forum and others trying to troubleshoot this but to no avail.

My system was working fine once upon a time. My resin usage was reasonable. I would probably replace every 2-3 months.

But recently it's really been smoking through the resins. :-)

Here's my setup, parameters, and suspicions:

I have 6 stage 100GPD RO/DI, 3 pre-filter, RO, 2 DI + Silica DI.

Here is the link to my membrane, 6 months old: http://www.purewaterclub.com/catalog/product_info.php?cPath=53_57&products_id=48

Tap water = 375 tds
TDS after pre-filters = ~150 tds
Pressure immediately before membrane = 60 psi
Water after membrane = 125 tds
Water after DI = 0-1, but quickly climbs as the DI nears exhaustion

My tap tds really changes by the time of the year. Right now it's high at 375 but gets lower in the winter - I think.

I previously used a self piercing saddle valve but I've since replaced this with a fitting directly to the copper. It seems to have improved my pressure.

So, I believe the rejection is around 98%. So I should see my RO TDS around 1-5, right?

It appears to me my membrane is not functioning correctly. I've trying flushing from 30-60 minutes and it doesn't seem to help. Could I have done something that would have damaged the membrane and caused it fail prematurely? I may have had lower pressure due the saddle valve but I didn't test pressure until I connected directly to the copper.

Any ideas or suggestions? Any help or assistance is appreciated.



05/17/2010, 08:34 AM
Todd your 450 flow restrictor is what would be used for a 50 GPD membrane
and your 100 GPD should have been running a 800 or 850.

Membranes generally last 2-3 years and the tight constriction of your 450 could
well have shortened your membrane life. The long flush didn't bring it around so
with your readings your membrane is your problem and needs replacement. I would
recommend going to a 75 GPD with a new restrictor either 550 or 600 mL rated for
the 75. 75 GPD membranes have a 98% rejection rate and 100 GPD have a 90%
rejection rate so the 75 is going to be better for you and conserve resin.

Your readings look good except for after RO, but tight constricton and water chemistry can cause a
membrane to fail in a short time period.


05/20/2010, 08:41 PM

Received the 75GPD membrane and replaced it with the 550ml restictor. RO is back in business and TDS after RO = 2-5.

However, my meter is showing TDS = 1 consistently after the resins. I've double checked with another meter and TDS = 1 after an hour or two of running. I have 2 - 10" housings w/ fresh Filter Guys resins + one with the ANION SILICA CARTRIDGE.

My question is: how can I tell the ANION SILICA CARTRIDGE is expired? My thought is even with my membrane failing, and my system smoking through the DI resins, my ANION SILICA CARTRIDGE should be preserved, correct? My understanding is it should only pull out silica, correct? Either way, I would think two 10" housing of fresh DI resin would be enough to pull this down to TDS = 0. Is my ANION SILICA CARTRIDGE expired?

Thanks again for the assistance.


05/20/2010, 09:22 PM
On a hunch moved my inline meter between the ANION SILICA DI and regular DI and saw my TDS = 0. So it appears my ANION SILICA cartridge was exausted prematurely as well and adding TDS back in the final polishing stage.

I replaced the ANION SILICA cartridge and TDS = 0. RO = 2. I'm hoping the resins last much longer this time.

All in all, an expensive lesson. I'm learning alot about RO/DI. :spin1:

Jim, thanks for the great support, products and service!


05/20/2010, 11:26 PM
You raise an interesting question and I'll have to run a test and get back to you.


05/21/2010, 08:14 PM
So, I swapped out the ANION silica cartridge with a fresh one. And my TDS dropped to 0. That held for a short time now has creeped nack up to 2.

I was disappointed to change out the $20 ANION cartridge so fast, but 2 of them?

Same thing applies as earlier in the thread. My RO TDS = 4 or so. When I put my inline TDS meter between the regular DI and ANION DI, my TDS = 0.

So I don't understand what's up with the ANION DI? My whole system w/ new membrane, new restrictor valve, and fresh regular resins appears to be working perfect. The ANION resin is adding back 2 TDS to my system.

Jim, any ideas what may be amiss?



05/22/2010, 08:43 AM
OK I had to test myself to see what your seeing. What you are seeing is an Ion charge coming off your silica resin and not bad water. Zero tds water is not truly zero but has a reading of .7. Your anion silica resin is also producing an ion charge which is pushing that .7 into a readable range of over that .7 fraction. Change the position of your silica cartridge into the first position and as long as your DI cartridge is OK you should have zero tds. I didn't run a cartridge long enough but that charge may also wear down after a period of time bring you back to zero.

Your standard mixed bed cartridge is a 60/40 blend of kation and anion resins. With a silica cartridge all you are doing is boosting the anion portion of your resin. When you see a silica booster cartridge the silica portion is always placed last in the cartridge or first to receive water. Water running through the whole resin cartridge bed removes the ion charge.


05/22/2010, 05:50 PM
Okay, I think I have it. The Anion Silica cartridge is intended to go first? I always thought since it was a "polishing" cartridge it should go last. I'll move this to the first position before my regular mixed bed. Thanks.

08/09/2010, 07:22 PM

I replaced my RO membrane in early May. At first, my post RO TDS= 3-5 and my resins lasted a good long time. But gradually my post RO TDS has risen 40,50,60,70. If I give it a good long flush I can get it back to 50 or so but never 3-5 like it was when it was new. The membrane is only 3 months old and my resins are depleting pretty fast again. My input pressure has stayed constant at 75. So I don't think my pre-filters are clogged yet. They're probably 6 months old. My input TDS = 400 and has stayed pretty constant. I have made probably a total of 300 gallons with the 75GPD membrane over that 3 month period. I know you've said high C02 can cause RO membranes to fail quicker. How can I test this? Will a marine CO2 test kit work on fresh water. And what constitutes high vs. okay?

Any other ideas that you can suggest that map to what I'm experiencing?

Any help is appreciated.



08/09/2010, 10:35 PM
Todd check to see if your system is still passing waste water or if it is just dripping. We have come across an instance where the water chemistry closes off the flow restrictor causing the membrane to foul.


08/10/2010, 08:04 PM
Jim, thanks for the quick response. I checked my waste water line and its definately passing water. I did a hour plus flush today and now my post RO TDS = 80. I saw similar things on my last membrane I replaced. They start at 0-5 TDS then quickly grow to 80+ TDS after 3-6 months. Flushing doesn't seem to help. I thought I had a problem with a mismatched restrictor valve on the last one but this seems to be a very similar problem. The membrane and restrictor I purchased from you are matchedup. It seems my membranes are clogging way way to soon. My tap water TDS = 420 (no water softener) and the waste water TDS = 580.

My prefilters were about 6 months old so I replaced them last night and it didn't appear to make one bit of difference other than my RO TDS going from 70 to 80.

The water coming of the waste line is a trickle of sorts but looks good. Is this something should take off and say soak in vinegar to get out any deposits?

Membrane = 3 months old and I've made maybe 2-300 gallons of water tops.

This is very frustrating. I don't know what else to do.

08/11/2010, 01:38 PM
Take the flow restrictor off and soak it in vinegar.

It sounds like your membrane and restrictor are calsifying from your bad water. Dont soar the membrane but run water for 20 minutes without the restrictor on and see if you can free up the membrane before putting the soaked restrictor back on.


08/11/2010, 06:38 PM
No change. I soaked the restrictor in vinegar and let the membrane flush again and it didn't help. The restrictor didn't seem clogged. My post RO TDS floats up to 80. Does this mean my membrane is toast? Everything I've read says input TDS=400+ should be okay. Maybe I was expecting 2 years out of the membrane and not 3. If I remove it is there a way to visibly tell the membrane is bad? I'm okay replacing the membrane if I knew what the cause was and how to prevent this from happening again. Is there anything else im my water chemistry that could cause this to happen? I have city well water from western Chicago suburbs (Algonquin) if that helps. Any other ideas?

08/11/2010, 06:40 PM
One other thing I forgot to mention. My production is down to a trickle. That is definitely a change from what then membrane was new.

What's my next option? A water softener before the input?

08/11/2010, 06:49 PM
Last post for tonight. I've been making my water in very small batches. 2-3g at a time and keeping in my pressure tank for top offs. I do full 30g or so every 2 weeks against the 75gpd membrane. I've been reading a little about tds creep. Could too many short cycles over 3 months cause the membrane to fail early? Should I be storing water in larger production batches?

08/12/2010, 08:37 AM
It does sound like your membrane is clogged and yes making short bursts of water can cause a clog. However tds creep would not be the cause as it is a short burst of tds common in all membranes which generally lasts less then a minute. We do expect more from a membrane but water chemistry can take them out very quickly some times. The only way you can see what's up with a clogged membrane in the state yours is in is to cut it open. Your problem could be just hard water or something your water treatment plant is doing to treat the water. It is very hard to pinpoint the problem but it is for sure something in the water. Repeated membrane failure points up the issue is on going.

You might want to look into a water softener and a softener company could provide some insight into your issues.


08/12/2010, 07:55 PM
Jim, thanks for the insight. I'll look into water storage and making more water in one session and a water softener..thanks.