RO Membranes and RO/DI Filters

d2mini · 11/27/2009, 10:23 PM

How do you know when to change the RO membrane? These are just as expensive as the rest of the ro/di filters combined. Do you need to change at the same time or do they last longer? Do you always change everything all at once or one at a time?

FranktheTankTx · 11/27/2009, 10:50 PM

Do you have a TDS meter? This would help greatly, as you could detect TDS present. RO membranes should have a 96-98% rejection rate - if you're worse than that, it's getting time to change the RO membrane.

ricde · 11/27/2009, 11:29 PM

+1 to Frank
Also check out the Spectrapure sponsor section on RC. They've got some great deals on membranes exclusively for the RC community.

The membrane usually last 2-3 years (depending on the input water purity) if cared for properly. I use color changing DI and change the sediment and carbon filters when the sediment filter shows a lot of gunk in it. TDS is always the best indicator of the filters though.

d2mini · 11/28/2009, 08:26 AM

Well i have a tds meter connected to the last stage. It came with my FilterGuys OceanReef+1 RO/DI system. The tds meter reads 2-3 on the way in and 0 on the way out. The first stage filter is nasty orange. The carbon in the DI I can't really see but the water in there looks brown. The other 2 filters look gray-ish. And of course the RO memberane i can't see. I've had the system for about a year.

Nereaga · 11/28/2009, 08:50 AM

What is the TDS of your tap water?

FranktheTankTx · 11/28/2009, 11:37 AM

Sounds like you should change your poly & carbon filter definitely. Is your DI resin the color changing type? 2-3 TDS from RO is just right, and sounds like your RO membrane is fine. If you haven't changed your other filters in a year, I would do so.

Summary

Change out the poly, carbon, & DI & use the RO membrane for another 6 months & test your TDS coming out of it again. You know you're at 2-3 TDS now. If you see a major jump in that number, change out your RO membrane. Sounds like you have another 6 months life it at least.

d2mini · 11/28/2009, 03:38 PM

Yes, my DI resin is the color changing type. I can't really see anything in it except that the bottom half seems to have brownish water in it. I went ahead and ordered a new filter set and I will get the RO membrane later like you said.

11/27/2009, 10:23 PM	#1
d2mini Registered Member Join Date: Nov 2008 Location: Houston, TX Posts: 10,344	RO Membranes and RO/DI Filters How do you know when to change the RO membrane? These are just as expensive as the rest of the ro/di filters combined. Do you need to change at the same time or do they last longer? Do you always change everything all at once or one at a time?

11/27/2009, 10:50 PM	#2
FranktheTankTx Registered Member Join Date: Dec 2007 Location: Texas Posts: 2,306	Do you have a TDS meter? This would help greatly, as you could detect TDS present. RO membranes should have a 96-98% rejection rate - if you're worse than that, it's getting time to change the RO membrane. __________________ Frank the Tank "What, I thought we were in the trust tree... in the nest? Are we not?" Current Tank Info: Custom Rimless 60g (30.5"x24.5"x18.5")

11/27/2009, 11:29 PM	#3
ricde Registered Member Join Date: May 2008 Location: Fayetteville, NC Posts: 452	+1 to Frank Also check out the Spectrapure sponsor section on RC. They've got some great deals on membranes exclusively for the RC community. The membrane usually last 2-3 years (depending on the input water purity) if cared for properly. I use color changing DI and change the sediment and carbon filters when the sediment filter shows a lot of gunk in it. TDS is always the best indicator of the filters though. Last edited by ricde; 11/27/2009 at 11:36 PM.

11/28/2009, 11:37 AM	#6
FranktheTankTx Registered Member Join Date: Dec 2007 Location: Texas Posts: 2,306	Sounds like you should change your poly & carbon filter definitely. Is your DI resin the color changing type? 2-3 TDS from RO is just right, and sounds like your RO membrane is fine. If you haven't changed your other filters in a year, I would do so. Summary Change out the poly, carbon, & DI & use the RO membrane for another 6 months & test your TDS coming out of it again. You know you're at 2-3 TDS now. If you see a major jump in that number, change out your RO membrane. Sounds like you have another 6 months life it at least. __________________ Frank the Tank "What, I thought we were in the trust tree... in the nest? Are we not?" Current Tank Info: Custom Rimless 60g (30.5"x24.5"x18.5")

11/28/2009, 08:26 AM	#4
d2mini Registered Member Join Date: Nov 2008 Location: Houston, TX Posts: 10,344	Well i have a tds meter connected to the last stage. It came with my FilterGuys OceanReef+1 RO/DI system. The tds meter reads 2-3 on the way in and 0 on the way out. The first stage filter is nasty orange. The carbon in the DI I can't really see but the water in there looks brown. The other 2 filters look gray-ish. And of course the RO memberane i can't see. I've had the system for about a year.

11/28/2009, 08:50 AM	#5
Nereaga Registered Member Join Date: Oct 2007 Location: Oley, Pa 19547 Posts: 1,513	What is the TDS of your tap water?

11/28/2009, 03:38 PM	#7
d2mini Registered Member Join Date: Nov 2008 Location: Houston, TX Posts: 10,344	Yes, my DI resin is the color changing type. I can't really see anything in it except that the bottom half seems to have brownish water in it. I went ahead and ordered a new filter set and I will get the RO membrane later like you said.