Ro/DI

scvc · 07-04-2007, 05:37 AM

I need some advice on my RO/DI. Prior to moving I only had a RO unit and I lived in a city with public utility water.

I am now in South Florida with a well and water softener and a RO/DI set up. the DI cartridge changed colors in less than 2 months. The other cartridges look fine. I guess my question is do I just need to plan on changing that cartridge every 6 weeks? do I need a different type of cartridge? or what about an additional cartridge? I had heard someone say that when on well water there was another cartridge I might need to add, but I do not know what it was.

I have seen that some of you are here in South Florida albeit spread around a bit, any suggestions would sure be a help.

chrisANDbarb · 07-04-2007, 05:51 AM

your RO membrane might be bad. how old is it, what brand and GPD is it, what is your TDS before and after the membrane(not after the DI)

Tangster · 07-04-2007, 06:58 AM

The D/I if its a dual or mixed bed color changing polymer/resins it needs to have the polymers/resins changed out when they change off to a white tan color from the deep red if thats the type you have ?
Now a R/O is good for several yrs if you changed the pre-filters as you should and ran a 1. Micron sediment filter. The chlorine and chlordanes in water is what deteriorates the membranes . Also the membranes will decrease in GPD output if the proper waste water rejection was not maintained . If you have a TDS meter and you really should as thats the only way to tell whats going on in there..
But when you break the unit down take the R/O membrane out and wrap it in a large plastic freezer bag and keep it wet and refrigerated to retard bacterial bloom . Then replace the pre filters and carbon and then recharge the D.I and you will be good to go. A R/O membrane will last 3 to 5 yrs if maintained properly ours here is now 3 yrs old.

scvc · 07-05-2007, 04:26 AM

This unit is an Aqua FX, 4 stage Barracuda RO/DI, 100 gpd. It does have a TDS meter, but I do not know if that is before or after the DI. It was installed the first week in May and has been used to fill the 120 gal plus top offs and some small changes since then. So, not much use as of yet. One of the instructions say "You will know when to change the reusable DI when the color has changed completely from the bottom up." Well, it did change from white to this brownish tan color. But darn, I would think I would get a lot more than this out of that filter.

Tangster · 07-05-2007, 05:44 AM

The TDS meter should be after the R/O not sure of the model you have But if properly plumbed then there D.I should be after the R/O so that there is no waste water passing through the D.I Now the life span of the D.I depends on the supplied water and I'd say maybe something is crossed up somewhere ? Our D.I last about 12 months and after filling a 180 and supplying a friends 55 and filling that also. Make sure the D.I is definitely down stream of the out let of the R/O. What does the TDS read ?

chrisANDbarb · 07-05-2007, 07:02 AM

on that unit you should be able to get 2 readings of TDS. one reading should say "in" this would be before any filters and will tell you what kind of water you are working with. the second reading should say "out" this will be after all filters and if the unit is working properly should be 0. to find out if the RO membrane is working properly, remove the DI cartridge and replace the cover to it (empty/ without the DI) run the unit for a few min. then take a TDS reading of the water going in, then a reading of the water going out. let just say that the water going in is at 100-TDS and out is 10-TDS that would mean that the RO membrane has a 90% rejection rate.if your rejection rate is 85% or lower i would say the membrane is shot. most RO membranes over 75gpd that are working properly have a rejection rate of about 90%. most membranes under 75gpd have a rejection rate of about 98%. thats why most people will recommend 75gpd membranes because the membrane does most of the work and the DI only has to clean up the remaining 2%= longer DI life. with a 90% rejection the DI has to remove the remaining 10%, let say your source water is 500-TDS, DI would have to remove 50-TDS=using lots of DI

scvc · 07-06-2007, 03:42 AM

I just checked it. Going in says 000, out is 003. Is there something wrong with that picture?

the_h2o_guru · 07-06-2007, 06:36 AM

Something is very wrong with that. What is the TDS of your tap water? Either way, something is getting through your membrane and killing off the DI. If there are a lot of nitrates or phosphates in your water, it may be slipping through the membrane and exhausting the DI. Nitrates and phosphates are something that the membrane can't reject too well. Usually, the membrane rejects at least half of them and the DI cleans up the rest. If you have a high level of either one, that's your culprit.

chrisANDbarb · 07-06-2007, 03:08 PM

Quote:

Originally Posted by scvc

I just checked it. Going in says 000, out is 003. Is there something wrong with that picture?

i think you might have your TDS meter hooked up backwards. "in" should be the water that is comming from your tap(and tested before any filters) and should be a higher number

scvc · 07-06-2007, 04:39 PM

It was all hooked up when I bought it, but that would sure make sense. that never quite made sense to me. i found the brochure on the unit and I am going to call the manufacturer on Monday and see what they can tell me. I will share that infor when I get it.