RO/DI Help

[tkeracer619]

If the intention of the dual membranes is to lower the amount of waste (Membranes wired in Series) and not produce more faster then the flowrate through the prefilters will remain the same I believe with a dual or single..

As it was explained to me by a filmtec engineer, the series membranes act as a single twice as long membrane. If you cut the waste ratio to 2:1 the second membrane doesn’t have the proper flow rate to keep from fouling. So where most people assume you cut the waste in half because that would be what common sense tells us, the reality is the waste ratio should remain 4:1 (or whatever you run at) to keep the membranes in good condition. So 4:1 with double product water gives you double waste water and total flow through the units.

Most people run a tighter waste than that with duals, no big deal, bulk membranes are cheap. I’m running my series spectrapure 99% membranes at 4:1 and after around 5 years and over 10s of thousands of gallons of product, they still are performing at a combined 99.5% rejection rate. This has saved me a ton on DI Resin.

 

[tkeracer619]

Also, I prefer to use a needle valve as a flow restrictor. This lets you keep it dialed in regardless of your water pressure or temperature of the source water.

 

[mcgyvr]

As it was explained to me by a filmtec engineer, the series membranes act as a single twice as long membrane. If you cut the waste ratio to 2:1 the second membrane doesn't have the proper flow rate to keep from fouling. So where most people assume you cut the waste in half because that would be what common sense tells us, the reality is the waste ratio should remain 4:1 (or whatever you run at) to keep the membranes in good condition. So 4:1 with double product water gives you double waste water and total flow through the units.

Most people run a tighter waste than that with duals, no big deal, bulk membranes are cheap. I'm running my series spectrapure 99% membranes at 4:1 and after around 5 years and over 10s of thousands of gallons of product, they still are performing at a combined 99.5% rejection rate. This has saved me a ton on DI Resin.

While I agree that running membranes in series may lead to a somewhat decreased lifespan I save the cost of multiple membranes each year just in the reduction in waste water... I'm on year 4 of my membranes and they are still going strong too..

 

[wrxreefer823]

That's my thought process as well. However since I went with the 90 instead of the 75, I'll see how that goes and maybe add a second if I see fit. The only reason I'm going single membrane for now is that the house pressure is right at the threshold of the requirement for a dual membrane setup. I'm going to pick up a couple of 70 gallon barrels tomorrow and then we'll be out of town for the weekend. Hopefully I can get it all up and running this time next week!

 

[Opus123]

It seems that your source may (please check by requesting your water quality report for your specific water vendor) use Chloramines which do require a bit more treatment to protect the membrane.. You may want to go with a block more suited for Chloramines..

Mine uses Chlorine which a single carbon block does just fine against..

Chloramines will not hurt the membrane, at least not as quickly as chlorine. From what I read on the manufacturers website, it would take a lot of chloramines to damage a membrane.

 

[mcgyvr]

Chloramines will not hurt the membrane, at least not as quickly as chlorine. From what I read on the manufacturers website, it would take a lot of chloramines to damage a membrane.

[MENTION=99003]Opus123[/MENTION] Yep..(kind of)
RO membranes typically tolerate 300 times the amount of Chloramines vs Chlorine but as Chloramines are basically just adding ammonia free Chlorine may still be present and still oxidize the membrane quickly..

Chloramines from my understanding also require more contact time/carbon,etc... so proper prefiltration is still quite important..

 

[wrxreefer823]

A bit off topic, but just for kicks and giggles I tested the water out of the tap and it's hovering right around 115 TDS, so I'm hoping it won't need too much filtration!


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[Opus123]

[MENTION=99003]Opus123[/MENTION] Yep..(kind of)
RO membranes typically tolerate 300 times the amount of Chloramines vs Chlorine but as Chloramines are basically just adding ammonia free Chlorine may still be present and still oxidize the membrane quickly..

Chloramines from my understanding also require more contact time/carbon,etc... so proper prefiltration is still quite important..

Can chloramines make it past the DI filter?

 

[Opus123]

A bit off topic, but just for kicks and giggles I tested the water out of the tap and it's hovering right around 115 TDS, so I'm hoping it won't need too much filtration!


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Take care of the chloramines/chlorine and it should using the spectrapure. My tds is over 400 at the tap and runs between 3 and 4 tds after my spectrapure membrane.

 

[mcgyvr]

Can chloramines make it past the DI filter?

DI resin will remove Chloramines and yes they "could" make it past and they will rapidly deplete the resins too..
You want to remove as much of the Chloramines in the prefilters (carbon) as you can..

 

[Opus123]

DI resin will remove Chloramines and yes they "could" make it past and they will rapidly deplete the resins too..
You want to remove as much of the Chloramines in the prefilters (carbon) as you can..

Interesting. We had a local guy claim his tank was destroyed by chloramines because the DI would not take the chloramines out.

 

[mcgyvr]

Interesting. We had a local guy claim his tank was destroyed by chloramines because the DI would not take the chloramines out.

If the resin was depleted/tunneled,etc...then its certainly possible..Of course there are tons of assumptions in this hobby that may or may not be correct...

 

[tkeracer619]

Interesting. We had a local guy claim his tank was destroyed by chloramines because the DI would not take the chloramines out.

I lost a tank to chloramines before I knew better. Everything exhausted way faster than I had expected. By the time I figured out what was going on, it was too late. If your prefilter isn't up to snuff your DI will burn rapidly.

 

[tkeracer619]

Chloramines will not hurt the membrane, at least not as quickly as chlorine. From what I read on the manufacturers website, it would take a lot of chloramines to damage a membrane.

Since Chloramines have a half life of around 20 days. Once the membrane is exposed to it, it remains exposed to it. Chlorine has a half life of several hours.

Also, when you are getting breakthrough, typically chlorine is much lower concentration since the carbon can remove so much more if it.

 

[Opus123]

From the Lenntech website:

"FILMTEC™ FT30 membrane has a 300,000 ppm-hour tolerance for chloramine, which implies that dechlorination is not required. However, since chloramines are formed by adding ammonia to chlorine, it is possible that free chlorine will be present. Since this free chlorine can be damaging to the membrane, dechlorination should still be considered. Residual chlorine can be reduced to harmless chlorides by chemical reducing agents."

 

[tkeracer619]

From the Lenntech website:

"FILMTEC™ FT30 membrane has a 300,000 ppm-hour tolerance for chloramine, which implies that dechlorination is not required. However, since chloramines are formed by adding ammonia to chlorine, it is possible that free chlorine will be present. Since this free chlorine can be damaging to the membrane, dechlorination should still be considered. Residual chlorine can be reduced to harmless chlorides by chemical reducing agents."

That’s interesting, my personal experience has not aligned with that. It must be due to free chlorine. I was burning membranes every year prior to significantly beefing up my carbon stages. Regardless, unless you enjoy buying DI by the cuft probably still a good idea to hit it hard at the carbon.

 

[wrxreefer823]

I'm honestly thinking of adding a prefilter just for sediment and going with three carbon blocks, then membrane, then 2 DI. Am I crazy?


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[Opus123]

I'm honestly thinking of adding a prefilter just for sediment and going with three carbon blocks, then membrane, then 2 DI. Am I crazy?


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I think that is overkill. I would go with a regular carbon block and then a PENTEK CHLORPLUS CARBON BLOCK or 2 PENTEK CHLORPLUS CARBON BLOCKs. Then just buy a kit to test for chloramines. Unless you are making a lot of water you will be fine and that should last you many months. As long as you don't let any chloramines thru, your DI will last you a long long time. The spectrapure ro membrane should yield you water with tds of 1, which means your 1 DI cartridge will produce around 4400 gallons of 0 tds water.

 

[wrxreefer823]

Gotcha. Okay, my total tank volume is 165, probably around 150 after sand and rock, maybe less. After that initial fill it's just top off and water changes.


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[tkeracer619]

Chlorplus goes BEFORE regular carbon.

The more the merrier.

I started using a chlorplus 20bb which is a size 4 big blue out in front of my system. (20x4.5” cart)

Then ended up just filtering the whole house with a 2.5cuft backwashing catalytic carbon tank and then a 48,000 grain softener. Tap water has no measurable chlorine or ammonia. Wife says it was the best aquarium purchase to date.