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Need to replace RO Filters and Membrane


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I bought a 5 stage RO kit from ebay like a year ago.... it looks exacly like this


However, the top filter says its a T/28, when it comes to membranes, what should I look for? I also use the system for drinking.


Here are my questions:


1. is 100gpd better than 50 gpd?

2. is 100gpd size same as 50gpd?

3. are all other filters the size standard?

4. should I buy a replacement kit from ebay? like this




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This is a photo and explaination of what a Dow Filmtec RO membrane and numbering system would look like:



You do not want a 100 GPD membrane, they are only 90% efficient versus 96-98% efficient for the 75 GPD or 50 GPD versions.


Yes they are the same physical size but the 100 is a NF or Nano Filter membrane while the 75 is a RO or Reverse Osmosis membrane, thats the 90% vs 96-98% difference.


Yes most other filters should be a standard 10" replacement.


Generally Ebay filters are not the same quality as reef filters as most are intended for drinking water and not a reef tank. The micron ratings are usually more coarse with drinking water systems as they are cheaper.


I would not buy the filters you linked to, they are 5 micron and you would be better served by a 1 micron or less prefilter, single 0.5 or 0.6 micron carbon block, a 75 GPD membrane and flow restrictor and use the empty housing for a vertical DI filter with just a few bucks and 15 minutes time to replumb it. Your reef tank will thank you for the addition of the DI.


Notice that vendor also neglects to tell you who makes the membrane which is not wise, it could be a knock off import and not even NSF approved.

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there is a company called www.airwaterice.com that has awesome prices on replacement filters.


I plan on doing an order in a day or so..



i also have a question.. how often should the membrane be replaced?


its been two years since i've replaced my filters lol but it still reads 001 on the TDS.


think i can get away with just doing the 3 stages and the DI?




btw i have a 10% code for airwaterice if you want it :) 29732

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To know when the membrane needs replaced you need three TDS readings, tap water, RO only and RO/DI. The RO only TDS should be in the 95%+ range of the tap water with a properly functioning RO membrane.


In most cases a membrane will last 18-36 months if you keep up with the prefilter and carbon block replacements every 6 months and disinfect the system at least annually if not every 6 months when you have it down for replacements, it only takes a few minutes.


The better the quality and lower the micron ranges of the prefilter and carbon block, the longer the membrane will last and better it will function. If you go with Air Water & Ice opt for their low micron filter set rather than the 10, 5 ,1 arrangement. The lower micron prefilter will do a better job of protecting the carbon blocks billions of tiny microscopic pores which is how it adsorbs chlorine and VOCs. If the carbon has to act as a secondary prefilter as in preceded by a high micron filter, then it will get fouled and not adsorb the chlorine which is what damages the membrane.

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