RO/DI membrane

[antdizzle]

my membrane is a 50 gpd membrane. I wana increase its output. is it as simple as switching the membrane to a bigger one ? would like to kick it up to 100. how much di resin do you think itll burn through ? Im guessing a decent amount in a short amount of time.

 

[RBursek]

If the membrane size is the same you can go larger, you will also have to change the restricter in the wast line to match the GPD of the new one. I would not sugest going to 100gpd most of those membranes only filter out 90% of TDS's where most others are 96-98% effecient. Membranes are rate at 77*F water at 60psi, any thing less will give you less flow anything more will give more flow. theFilterguys is a great place to call and get what you need, one of the best customer service any where. I also posted a flow calculater site that will let you know what gpd you can expect from a given membrane based on incoming TDS;s and water pressure and temp.
The Filter Guys

RO Membrane Performance Calculator

 

[melev]

What consumes the DI resin is the TDS coming out of the membrane. The higher that number, the more quickly the resin is used up. If the membrane is efficient, this number should be nice and low.

I have a 150gpd membrane with a booster pump that keeps the water pressure between 92 and 102 PSI, and the TDS coming out of the membrane is 1. I've been using the same DI cartridge since August 2009, and it still appears to be at least one-third unspent.

A slower membrane such as the 75gpd one is considered the best efficiency for common water pressure in our homes, but with that comes slower production rates. With everything optimum, you could expect to get 3.13 gallons of RO/DI water per hour. With 100gpd, you'd get 4.16gph. I'm impatient, and want to make what I need quickly. With my boosted 150gpd system, it'll produce 5g in 40 minutes.

 

[RBursek]

I did not mention this in my prior post but high CO2 in your water wil eat up DI resin also. Which has nothing to do with the amount of TDS going into it, but yes hight TDS's going in will also use it up faster, that is why a 100gpd membranes at 90% effecientcy are not the favorite. The Filter Guys have a 75gpd membraine that will give you 90gpd at 77* at 60psi and has a 96-98% rejection rate.

 

[AZDesertRat]

All 100 GPD membranes are not the same. The 100 GPD that Melev uses is a GE brand which is the same 96-98% rejection rate as the Dow Filmtec 75 GPD. The GPD is even the same since Dow and GE rate them differently. They both do 75 GPD at 50 psi, 90 GPD at 60 psi and 100 GPD at 65 psi. The 100 to stay away from and the one RBursek is referring to is the 100 GPD Dow Filmtec which is not a true RO membrane and is only 90% rejection rate, it produces wate rfaster but is not as pure so eats resin.
You might check out this Sales flyer where you can get an individually hand tested and guaranteed better than 98% rejection rate membrane for $40 on sale. Mine is averaging 99.35% rejection which really extends the life of DI resin. To put it in perspective, for every 2% you increase the membranes efficiency you DOUBLE the life of your DI resin. That can be a significant cost savings over time.
SpectraPure Customer Appreciation SALE! 20% - 50% off
If you get a larger membrane make sure you get the flow restrictor to go with it, I prefer capillary tube type restrictors which you take a few minutes and fine tune to your exact conditions for best performance and membrane life.

Hey Marc, how are things? Haven't heard much from you since I am not welcome on RC anymore. Hope all is well.

 

[melev]

I'm good, AZ. Matter of fact, I'm here and no longer on RC.

 

[Troylee]

what i have recently noticed is i have a kent hi-s 35gpd unit and i recently replaced the membrane with a off the wall one from air water ice it was like 40$ vs the 100$ for a kent.....big mistake!!!! i have had all sorts of diatom outbreaks since... there def not all the same...... i guess you get what you pay for...

 

[AZDesertRat]

The SpectraSelect series membranes are on sale for $40 here and are individually hand tested and guaranteed in writing to be better than 98% rejection rate, they don't come any better or cheaper for a top quality RO membrane.
SpectraPure Customer Appreciation SALE! 20% - 50% off

My personal Select membrane is averaging 99.35% rejection with RO only and is approaching two years old now with no drop off in quality.