freddie40
06/02/2007, 11:20 AM
3 years ago I bought a RO/DI off of Ebay for $60 plus shipping. It was advertised as a 75 GPD but never produced more than 25GPD.
Last year I replaced the Chloramine and DI with refillable ones from The Filter Guys and the 2 other pre-filters with new ones from Wal-Mart.
I am not complaining because mt TDS was always fine, but the flow rate sucked.
This year I looked at things a bit more seriously and made some discoveries that I would share.
First I replaced the DI resin. Did you realize that enough DI resin to fit in a 10" horizontal cartridge only treats 2000 TDS. A full size vertical cartridge should handle about 6800 TDS.
This means it depends on what your TDS is doing into the DI as to how long the resin will last.
My TDS after the RO was 10, so the DI resin should last for 200 gallons.
However, with a 96% rejection rate the TDS should have been lower than 10, making the DI last longer. My tap water has a TDS of about 140.
So, I replaced the RO membrance ($45 from The Filter Guys) with a 75GPD at 98% rejection. I also added a Dual inline TDS meter to be safe.
Low and behold, after replacing the RO membranve I really am getting 75 GPD and my TDS after the RO is now 4. Does it really matter, maybe not. However, the water that you put in a tank is the easiest thing to control, so the purer the better.
One final thought. If one vertical cartridge can handle 6800 TDS, and your tap water is 200 TDS this means that you can probably process 34 gallons if you are using a DI only system. Since the Resin costs $53 for a 4 pack (including shipping) and 1 pack will fill a vertical cartridge the cost is about 50 cents per gallon. I will not try to draw any conclusions from this.
Any comments. I got the 2000 and 6800 numbers from the Filter Guys.
Dave
Last year I replaced the Chloramine and DI with refillable ones from The Filter Guys and the 2 other pre-filters with new ones from Wal-Mart.
I am not complaining because mt TDS was always fine, but the flow rate sucked.
This year I looked at things a bit more seriously and made some discoveries that I would share.
First I replaced the DI resin. Did you realize that enough DI resin to fit in a 10" horizontal cartridge only treats 2000 TDS. A full size vertical cartridge should handle about 6800 TDS.
This means it depends on what your TDS is doing into the DI as to how long the resin will last.
My TDS after the RO was 10, so the DI resin should last for 200 gallons.
However, with a 96% rejection rate the TDS should have been lower than 10, making the DI last longer. My tap water has a TDS of about 140.
So, I replaced the RO membrance ($45 from The Filter Guys) with a 75GPD at 98% rejection. I also added a Dual inline TDS meter to be safe.
Low and behold, after replacing the RO membranve I really am getting 75 GPD and my TDS after the RO is now 4. Does it really matter, maybe not. However, the water that you put in a tank is the easiest thing to control, so the purer the better.
One final thought. If one vertical cartridge can handle 6800 TDS, and your tap water is 200 TDS this means that you can probably process 34 gallons if you are using a DI only system. Since the Resin costs $53 for a 4 pack (including shipping) and 1 pack will fill a vertical cartridge the cost is about 50 cents per gallon. I will not try to draw any conclusions from this.
Any comments. I got the 2000 and 6800 numbers from the Filter Guys.
Dave