Exhausting DI - Need Insight Please

[CUSE1315]

About a year ago i started using RODI and cannot seen to comprehend why i have used 8 LBS of DI. I am on city water and my TDS is around 260 to 290 Consistenty.

Background:

Started with 6 stage RODI from ebay 50GPD.
Installed a flush and used for a few months. It was not selling to do the trick so 6 months in i added a 90 GPD high efficieny spectra pure membrane.

Still no noticeable difference as i was getting 50 to 75 gallon of 0 TDS water per DI.

I then switched to a 5 stage 90GPD spectrapure RODI unit. I am currently running 1 micron sediment. Carbon. 99% membrane and then dual DI. I am getting 9 to 11 after my membrane.


I then decided to add a booster this increased my pressure from 43 to 70.

I am looking for some help it is driving me crazy how much DI I an using and now i am getting 20TDS after my membrane.

I have changed my filters 3 times in a year.

Someone please help me solve this.

 

[cougareyes]

Since you just put in a new system I'm at a loss also, my first instinct would be to replace the membrane. I get my supplies and got my unit from brs. It's a 75gpd and I'm not sure how much I make but I change my filters about 3 times a year, I always flush my membrane and haven't had to change it over 4 years now. My pressure runs around 60 and my water is hard, around 450 tds going in and always 0 coming out. If it's not the membrane maybe try some different filter supplies.

 

[runningrandy04]

Hey there, sorry to hear about your membrane going bad.
I believe it's due to the chlorine in your water. I looked at your cities water report and it looks to have .5-3.5 ppm chlorine. Only the carbon can filter that out and any chlorine that makes it to the membrane destroys it. Carbon filters also need an on/off cycle in order to recover from the chlorine. There is a good BRS video on carbon filters with Ro/Di.

Ps You shouldn't be getting more than 3tds after the membrane. If so, check the ratio of waste to clean water volume. Should be 4:1

 

[amcvay1979]

Did you change your restrictor valve after you went from a 50 to a 90 gpd membrane? What are your rejection rates? You should be getting 1 gallon of pure water to 4 gallons of waste water, roughly.

I had a similar problem and what my solution was is this; my local water dept uses Chloramines to sanitize the water. Then my incoming water ph is around 9.0, really high. When high ph water is combined with chloramines, it will literally destroy and eat away RO membranes. So I added 2 of the BRS Chloramine Carbon cartridges to my system. So I have the BRS sediment, 2 BRS Carbon blocks, RO Membrane and a dual DI resin cartridge. My input TDS is about 150, after the RO it's down to 6-7, after DI it's 0 and has remained zero for months now.

Before the Chloramine Carbon blocks x 2, my DI resin would last about a month. So check with your local water dept and ask if they use Chloramines, I'm sure they probably do. Then check your input water Ph. If it's over 7.2 you'll want to buy the BRS filter change kit and use their Sediment, 2 Chloramine Carbon Blocks and DI resin. Best change I've ever made. Saving tons of $$$ now.

Good luck!

 

[reefgeezer]

Forgive me for asking if you already know but... How do you operate the system? Long or short periods of water production? I ask because there is a small amount of high TDS water that bypasses the membrane when the unit is first started. The DI resin absorbs the excess impurities so you don't see it. However, if you turn the unit on and off a lot, it will consume the DI resin much quicker than if you start the unit and let it run for long periods.

If you're already running the unit for long periods already, I'd +1 the chloramine issue.

 

[amcvay1979]

I run my RO/DI on a float switch and it runs for very short times so when I exhausted my DI resin I thought this was why. After I switched to Chloramine specific carbon blocks I still run a float valve to the sump and ATO from my RO/DI. It's still working well for me after a few months of the BRS Chloramine filters and my DI resin is still reading zero. It's amazing how chloramines can screw things up royally

 

[amcvay1979]

I flush my RO membrane weekly to combat this, even when I do, the TDS starts at about 70 ish, then gets down to 6 or 7 in a few minutes. Then I let it run normally into the drain for about 5 min to let it stretch its legs a bit, then right back onto the float switch.

 

[reefgeezer]

I run my RO/DI on a float switch and it runs for very short times so when I exhausted my DI resin I thought this was why. After I switched to Chloramine specific carbon blocks I still run a float valve to the sump and ATO from my RO/DI. It's still working well for me after a few months of the BRS Chloramine filters and my DI resin is still reading zero. It's amazing how chloramines can screw things up royally

Maybe someone else will chime in... I thought there was nothing you could do to prevent the initial bypass when water first starts to pass through the membrane. I thought a float switch driven system in particular runs for very short periods and creates a lot of bypass water. The chloramine blocks may be extending the time it takes the DI to be exhausted but, IME, not running it for short periods will really extend it.

I run my El-Cheapo RO unit that has a simple gross filter and carbon block to make at least 5 gallons at a time for water changes and 20-30 gallons at a time for filling the ATO container (Brute). My city water is in the 300-400 TDS range. I've never kept track of how much water I get from a single 10" cartridge of DI resin, but I'm certain it's more than a couple hundred gallons. I once tried to run it on a float switch for my ATO. It exhausted the DI in a few weeks. I evaporate about 1.5 gallons per day so that's maybe 40 gallons. When I complained here @ RC, someone set me straight.

 

[amcvay1979]

I believe you are correct, the initial high TDS spike is probably lessened by the chloramine filters and it has to be the 1 thing that has kept my dual DI canister from exhausting quickly.

That and the weekly flushes help keep the RO Membrane clean of any buildup or chloramines that would chew it up.

 

[Buckeye Hydro]

Cuse1315 - be happy to get your system squared away with you. Please give us a call when you are in front of the system if you'd like help troubleshooting it. Should only take a few minutes.

Russ
513-312-2343

 

[Buckeye Hydro]

Guys - there is a difference between a float SWITCH and a float VALVE.

A float switch is an electrical switch.

A float valve is a mechanical valve that operates like the valve in your toilet tank.

When you first turn on any RO system, the first water that comes out of the system won't be terribly clean. Here's some data from two test runs with a 75 gpd RO membrane:

You'll see that after about 60 seconds the TDS of the permeate (RO water) is down where you'd expect it.

So if you have your system set up such that it only comes on for a couple/few minutes at a time - yes - you'll significantly shorten the life of the DI resin.

Russ