RODI unit question?

[StikHedRon]

I have the brs 5 stage and use their nuke grade di resin. The last two refills I have tracked my production out of it and it has been 150 give or take 10 gals on the high side. My TDS is 5-6 into the di stage and I change the resin as soon as it jumps to 1. What can I do to get more water volume out of my resin? My psi runs about 55 also. Any tricks or tweaks would be appreciated.

 

[bluewaterbruce]

IMO .. You should be getting way more product water than that out of that resin. The membrane might be blown and I don't think the TDS reading before the DI is correct. I get about 400 to 500 gal. out of it before changing filters or resin. My TDS reading before the DI is usually 2 to maybe 4.
The only other advice is when starting a batch of water, divert the product water for a minute before the DI until the TDS number drops to normal levels. This will extend the life of the resin.

 

[kschweer]

Are you on well water? Well water can be very high in co2 which can eat through your di resin very quickly.

 

[StikHedRon]

I am on city water, how would I be able to check the co2 content of my water to see if this is an issue?

 

[kschweer]

I don't think I have heard this as an issue with city water but it's easy to check so it can't hurt. You need to take the pH reading and KH reading of your water and plug it into this calculator.
http://www.fishfriend.com/aquarium_co2_calculator.html

Also with the dual membrane systems the rejection rate is very important. Do you know your rejection rate?

 

[salttanklife]

Have you tried back flushing the system when you get a tds reading to clean it out?

 

[AZDesertRat]

CO2 can be a DI killer and it often goes unnoticed or unchecked.

We have CO2 here in Phoenix and when i was using regular nuclear or semicionductor grade resins I would only get 150 +/- gallons like you. I switched to Spectrapure and my first DI lasted 830 measured gallons and it has been over 1000 gallons ever since, huge difference!

You can check the pH and alkalinity of your RO only water and use this nomograph to get close or Spectrapure sells a CO2 test kit to get more precise:
FAQ

Carbon Dioxide Test Kit


How to test for CO2 and what problems CO2 may cause... - Reef Central Online Community

 

[StikHedRon]

This is all pretty confusing to me, I will check the co2 when I get home tonight. I checked that Spectapure sight and they have tons of different types of DI resin. I will have to call them to see what would be best for my application. I appreciate the advice.

 

[AZDesertRat]

Their SilicaBuster is blended specifically for reef use and is my resin of choice if you have a single DI and used in conjunction with their MaxCap if you have dual DI. They also no offer Super versions of each which has 30% more capacity. I installed my first Super cartridge about 6 months ago so have at least another 8-9 months before it exhausts I hope.

 

[SloppyJ]

I knew AZ was going to comment. He can't stay away from the municipal water discussions

 

[StikHedRon]

Their SilicaBuster is blended specifically for reef use and is my resin of choice if you have a single DI and used in cnjunction with their MaxCap if you have dual DI. They also no offer Super versions of each which has 30% more capacity. I installed my first Super cartridge about 6 months ago so have at least another 8-9 months before it exhausts I hope.

So you just buy their cartridge and resin all in one for refills?

 

[AZDesertRat]

I buy the replacement cartridges prefilled. I found buying bulk resin is not the answer since the unused portion goes bad before you can use it all up. Since they last me over a year each and resin has a 6 month shelf life even when packed and stored properly it would not be cost effective for me. They also pack their cartridges in a special layered way to take advantage or pH changes internally within the resins and is another key to their success.

 

[StikHedRon]

If I do have a high CO2 level in my water will upgrading from a BRS unit to the MaxCap 90gpd be a wise choice or even an effective choice?

 

[AZDesertRat]

CO2 passes through any membrane but the rejection rate gained by going from whatever your is now to their 99% guaranteed rejection rate can make a huge difference in DI life with or without CO2. For every 2% you can increase the rejection rate you double your DI life.

 

[StikHedRon]

Thanks, This sounds like a simple fix if I want to increase my DI life. Invest in a quality RODI unit! Thanks you are quite the RODI unit guru!

 

[AZDesertRat]

I wouldn't get rid of what you have unless you could sell it for a good price which is tough to do.
At your first or next 6 month filter change I would invest in better filters though like 0.5 or no larger than 1.0 micron sediment and carbon block, toss the unneeded second carbon block and turn that empty caniste rinto a dual DI to get bang for your buck. I would also monitor your rejection rate and your waste ratio to make sure you are as efficient as you can be. If the membrane rejection rate is less than say 97% I might think about a new 99% membrane and if the waste ratio is not where it should be a simple $5-$6 capillary tube flow restrictor could fix that when you trim it to fit your exact unique conditions.
Your housings, bracket and fittings are quality components its just the internals that may need improvement.

 

[StikHedRon]

How do I monitor rejection rate?

 

[AZDesertRat]

Using your handheld TDS meter and a squeaky clean clear glass drinking water glass washed by hand in extremely hot water so it doesn't have any dishwasher soap residue or anti spotting agents to skew the readings take a sample of your tap water and insert the meter letting it stabilize. Record the reading, triple rinse the glass and meter in RO/DI or distilled water then take a sample of the RO only water directly from RO by disconnecting the line between the RO and the DI to fill the glass. Again, insert the meter, let it stabilize and write the reading down. Those two numbers are used to calculate the rejection rate but while you are at it do another triple rinse and sample your RO/DI directly from the unit, take the reading and do a final triple rinse so both the meter and the glass are clean for next use.

Take the tap TDS number and subtract the RO only TDS, divide that number by the original tap TDS then multiply it by 100 for your rejection rate. An example using my readings of 560 tap TDS and 2 RO TDS goes like this: 560-2= 558, 558/560= .9964, .9964x100= 99.64% rejection rate. Out of a 6+ year old RO membrane that has never been changed is pretty good. Dow Filmtec membranes should be somewhere between 96 and 98% off the shelf but not always and when tested most come in around 96-97%.