DI exhausts after two water changes

[Tom Toro]

Any lead on a great DI resin that doesn't exhaust as quickly as most? On my r/o units and after a 2 50 gallon water changes and two weeks worth of evap, I need to change out the cartridge. My evap level is around 2.5gallons a day.

I have 357 going in, 4 going to the resin and 0 after the resin, but I'm changing every couple to three weeks. Is this about normal? I'm using brs nuclear grade color changer.

[Manoj's Reef]

I am by no means very good at this subject but will take a stab from what I have read so far.

The rapid depletion of DI is usually due to membrane being inefficient. Also pre treating the water before it goes in also helps. There was a thread on R2R on this subject.

[jimsflies]

How old are your membranes? 4 seems like a lot post RO. Do you have a carbon stage and how old is that?

[Tom Toro]

How old are your membranes? 4 seems like a lot post RO. Do you have a carbon stage and how old is that?

Both changed out last year, but I do have rough well water. I have whole house filter, softener and then the r/o units. I just changed the other four stages two weeks ago. I'm using the 75gpd tfm can't remember the brand.

[rmalone]

Whats killing you is that your not running the ro for 15-20min before sending it to the DI resin. When you first pressure up the ro membrane it will give 2-3gal of high tds water. On my membrane, which ends giving about 1ppm, it will start at about 140ppm and over the course of 15 min or so gradually drop to 1ppm. So if 1gallon of water at say 80ppm hits the resin it burns as much resin as 80g at 1ppm.

Spectra pure sells a nice little 2 way valve that lets you bypass the resin and just dump that initial high tds water.

[Tom Toro]

Whats killing you is that your not running the ro for 15-20min before sending it to the DI resin. When you first pressure up the ro membrane it will give 2-3gal of high tds water. On my membrane, which ends giving about 1ppm, it will start at about 140ppm and over the course of 15 min or so gradually drop to 1ppm. So if 1gallon of water at say 80ppm hits the resin it burns as much resin as 80g at 1ppm.

Spectra pure sells a nice little 2 way valve that lets you bypass the resin and just dump that initial high tds water.

That makes a lot of sense. I can bypass it myself with some valves. Also, if that's the case, then my ato water (5 gal bucket) is always wasting my resin since it only asks for about a half gallon at a time. I should make it gravity feed from a larger reservoir that I fill once a week.

Thanks for the help, Folks!

[dentdominator]

Hey Tom,

I had the same problem with the hard water in my house. I got tiered of changing the single DI unit frequently so I made a 4 stage DI unit and now it takes 3 - 4 months to exhaust the resin to 002 ppm. I've even gone longer up to 6 months and I think the meter read 005 ppm.

[MyNemesis]

If you have a RO Membrane flush bypass, you should flush the membrane for three minutes before and after every time you use the unit. As RMalone said, this saves the DI Resin. I have a meter before the DI unit and you watch it go down, then turn the flush off after it is at a low level. The guys at BRS told me the three minute deal and it really does help.

[Tom Toro]

Hey Alex,
Yeah, your setup is nice and automated. 6 months would be great! I'm switching it out every couple of weeks. I think you already do the large reservoir for top off, right?

John, I'll try the flush. I have it only one of my r/o units, but if it helps a little, I'll be happy.

[Flynnstone]

i myself am a little confused as why you would need to run the water for 3 minutes. would this be from algea that is living inside of the ro membrane housing? i dont believe anything can really leach through the membrane, so it must be from another source. my dual DI last for approx. 6-8 months, but the unit is in a dark closet. evap is at least 2 gallons a day, water changes are 50g monthly. top off water is being added every few minutes directly from the ro/di unit, maybe this is why it works well for me? moss dont grow on a rolling stone.

[rmalone]

well I honestly haven't looked into why tds is a ton higher for the first several min after pressuring up the system but I'm guessing it has to do with non ro blowing past the membrane until pressures on either side of the membrane hit an equillibrium. Higher/consistent water pressure, to a certain point, also tends to create cleaner ro water. You also see "tds creep" in ro systems when using a pressure tank beacause they make small amounts of water often, rather than large amounts all at once. When using di after ro you don't see this creep because the di eats it up. You could probably combine the right resins and not even use ro at all, but lord would it be spendy.

[CalmSeasQuest]

+1 on TDS Creep - TDS will be much higher for the first few minutes of starting the RO. Run the RO for a few minutes bypassing the DI. It's much more efficient to make water in larger quantities, rather then a few gallons at a time.

Increase feed Water Pressure - For reference, I have ~325 TDS well water. My BRS RO was creating 3 TDS water using house water pressure of 50~60 PSI. I installed a pressure pump and adjusted the input pressure to 90 PSI. This not only nearly doubled the volume of water made, but lowered the RO output water TDS to 1 (one) resulting in the DI resin lasting 3 times longer.

[binford4000]

I was wondering how much water pressure you running into the membrane,I have found that since I imstalled a booster pump and started useing carbon block filters the di last much longer. The higher the water pressure into the membrane the better it will perform.It also helps greatly if you run your water to ro after the water softner if you haven't done so.. I also found useing a seperate final stage di helps with the tds creep if it's installed below the the containers inlet so that water must go uphill

http://i825.photobucket.com/albums/zz179/binford4000/cr%20members%20tank/DSC01441.jpg

seperate final stage di

http://i825.photobucket.com/albums/zz179/binford4000/cr%20members%20tank/DSC01430.jpg

booster pump

[Flynnstone]

i bought a booster pump prior to checking my current water pressure. i have city water and my pressure is already at 90, so i dont need the pump. but keeping higher pressures would increase the life of the ro membrane due to the fact that more can be forced through it. also over time the pores would clog up and the TDS going through it would decrease. so the older the membrane the longer that the DI resin will last, but the waste water would increase too.
i am still at a loss why the TDS reads high at first.... maybe the membrane is breaking down? bacteria that is eating at the material trapped in the membrane?

[MyNemesis]

"TDS creep, a phenomenon that occurs with all RO systems, causes a rise in product water TDS when RO systems are not in use. This rise in TDS occurs because concentrated water rests on the reject side of the membrane element while low mineral content water rests on the product water side of the membrane element. When no pressure is applied to the membrane element, these concentrations will slowly tend to reach equilibrium through the natural processes of diffusion and osmosis. As a result, rejection at system start-up is often less than the true capabilities of the RO system. A flush kit allows installers to lessen TDS creep, resulting in better quality water when the system is used after periods of inactivity." Taken from a flush kit sales memoranda online

[FlynnFish]

"TDS creep, a phenomenon that occurs with all RO systems, causes a rise in product water TDS when RO systems are not in use. This rise in TDS occurs because concentrated water rests on the reject side of the membrane element while low mineral content water rests on the product water side of the membrane element. When no pressure is applied to the membrane element, these concentrations will slowly tend to reach equilibrium through the natural processes of diffusion and osmosis. As a result, rejection at system start-up is often less than the true capabilities of the RO system. A flush kit allows installers to lessen TDS creep, resulting in better quality water when the system is used after periods of inactivity." Taken from a flush kit sales memoranda online

that is awesome info!!!! so the time frame between the cycles would relate to the amount that is able to eqaualize, and also the initial concentration of TDS into the membrane, combined that would dictate the severity on the DI resin.

this site is awesome !!!!!

[AZDesertRat]

TDS creep happens with all RO membranes and a flush kit is of no value for this other than to lighten your wallet. Think about it, the flush kit installs on the waste line and bypasses the flow restrictor so you temporarily increase the flow rate to waste.
The TDS creep water is on the TREATED side of the membrane already so you can flush all day on the waste side without affecting the treated side. Its a way to get in your pocket.

You said you have domestic well water so your problem is more than likely CO2 in the water which is tough on DI resin and cannot be measured as TDS so does not show up. Your membrane is doing a very good job in reducing the 375 or whatever it was TDS down to 4, thats almost 99% rejection rate which is much better than most systems are capable of.

Short of building a degassing station to reduce the TDS your best bet is to try Spectrapures custom blended DI resins, they are guaranteed to outperform any other resin on the market and they do work. My tap TDS is between 530 and 850 and we do have a CO2 problem here, with my old AWI Typhoon III system I could never get over 150 gallons of 0-1 TDS RO/DI water no matter which resin I used, what brand it was or how fresh it was. I fought this ofr about 5 years before purchasing a Spectrapure MaxCap system. My very first DI cartridge lasted 830 measured gallons right out of the box and the next was over 1000 gallons with no other changes.

They have tens of thousands of hours testing every resin on the market that has led to blending their own in-house so they can control its quality. Its as low as $18 a full 20 oz cartridge on sale and the SilicaBuster is probably what you need.
Untitled Document (http://www.spectrapure.com/email/customer-appreciation.html)

If you have dual DI such as I do then the MaxCap/SilicaBuster combination is what I would suggest. There really is a difference. I tried straight from Resin Depot, AWI, PurelyH2o, Buckeye and many others and was even buying it in factory 50 lb sealed bags and boxes and vacuum sealing it for my friends in group buys. We all gave up and use only Spectrapure now.

TDS is not really as n=bad as it seems, its usually only a few ounces of water surrounding the membrane inside the housing and its no more than 1/2 the tap water TDS and usually much less than that. A few ounces is not going to kill a DI cartridge but it is a good idea to make water in larger less frequent batches so you get good long filter runs to flush the membrane well. If you make wate rnnually you can install a tee and ball valve between the RO membrane and the DI filter so you can open it and flush the first few ounces of treated RO water to waste so it does not get to the resin. Again this is treated wate ryou are flushing not waste like the fluh valve you see advertised do.

[Tom Toro]

Thanks for the work, AZ! Easy to read and understand. I bought the membranes from Spectrapure, but nothing else. When I run out of my current resin, I'll give their's a shot.




TDS creep happens with all RO membranes and a flush kit is of no value for this other than to lighten your wallet. Think about it, the flush kit installs on the waste line and bypasses the flow restrictor so you temporarily increase the flow rate to waste.
The TDS creep water is on the TREATED side of the membrane already so you can flush all day on the waste side without affecting the treated side. Its a way to get in your pocket.

You said you have domestic well water so your problem is more than likely CO2 in the water which is tough on DI resin and cannot be measured as TDS so does not show up. Your membrane is doing a very good job in reducing the 375 or whatever it was TDS down to 4, thats almost 99% rejection rate which is much better than most systems are capable of.

Short of building a degassing station to reduce the TDS your best bet is to try Spectrapures custom blended DI resins, they are guaranteed to outperform any other resin on the market and they do work. My tap TDS is between 530 and 850 and we do have a CO2 problem here, with my old AWI Typhoon III system I could never get over 150 gallons of 0-1 TDS RO/DI water no matter which resin I used, what brand it was or how fresh it was. I fought this ofr about 5 years before purchasing a Spectrapure MaxCap system. My very first DI cartridge lasted 830 measured gallons right out of the box and the next was over 1000 gallons with no other changes.

They have tens of thousands of hours testing every resin on the market that has led to blending their own in-house so they can control its quality. Its as low as $18 a full 20 oz cartridge on sale and the SilicaBuster is probably what you need.
Untitled Document (http://www.spectrapure.com/email/customer-appreciation.html)

If you have dual DI such as I do then the MaxCap/SilicaBuster combination is what I would suggest. There really is a difference. I tried straight from Resin Depot, AWI, PurelyH2o, Buckeye and many others and was even buying it in factory 50 lb sealed bags and boxes and vacuum sealing it for my friends in group buys. We all gave up and use only Spectrapure now.

TDS is not really as n=bad as it seems, its usually only a few ounces of water surrounding the membrane inside the housing and its no more than 1/2 the tap water TDS and usually much less than that. A few ounces is not going to kill a DI cartridge but it is a good idea to make water in larger less frequent batches so you get good long filter runs to flush the membrane well. If you make wate rnnually you can install a tee and ball valve between the RO membrane and the DI filter so you can open it and flush the first few ounces of treated RO water to waste so it does not get to the resin. Again this is treated wate ryou are flushing not waste like the fluh valve you see advertised do.