View Full Version : New Filters.

03/15/2009, 08:40 PM
I purchased a BFS-161 Premium Series 75 gpd RO/DI System last year from you. I saw you advised someone else to use replacement filters :

BFS-240 2-pack, Specialty Sediment Cartridge, 1 Micron Depth Filter - $7.99
BFS-2 Carbon block cartridge - The Chlorine Guzzler, 10-inch - $11.49

Is that what I would use?


Buckeye Hydro
03/16/2009, 04:02 AM
Yes sir.

Do you also need a refill for your DI resin cartridge?


03/16/2009, 05:57 AM
I don't know. How can I tell?

Buckeye Hydro
03/16/2009, 06:04 AM
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. The Matrikx+1 (“Chlorine Guzzler”) for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker then would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!


In this hobby we measure Total Dissolved Solids in parts per million, or "ppm." We often try to measure TDS down near 0 ppm. Because this TDS level is so low, we have to keep in mind the sensitivity of the meter used to measure it, and the technique used to measure the tds.

Nearly any contamination in the sample container will cause an erroneous TDS measurement. Some plastic containers are difficult to get absolutely clean, and although they appear clean, they are not. An easy standard approach is to use a drinking glass as a sample container - use one right out of the dishwasher. Obviously, keep your fingers away from the inside surface of the glass.

Calibrate your meter. Use a calibration fluid generally in the range of the tds measurements you'll be taking. Some meters require a specific tds calibration fluid (e.g., 800 ppm), regardless of the tds levels in your samples.

Be careful with how you take your samples. Let's say you intend to measure the TDS in your 1) DI water, 2) RO water, and 3) tap water. Start with the cleanest of the three - the DI water. After letting the system run for a sufficient period of time that you are sure the tds levels have stabilized (to assure you are not measuring tds creep water), rinse the sample container two or three times with the water you intend to sample, and then fill the sample container with sufficient DI water to take a reading.

Now on to the RO water. The water we are interested in here is the permeate – i.e., the water that has been purified by the RO membrane – not the waste water. Make sure you understand which is which before taking the sample. Most RODI systems other than Buckeye Systems are not plumbed to facilitate taking a sample of the permeate. If that is the case, you’ll need to unhook some tubing – likely where the tubing attaches to the “in” port on the DI housing in order to take this sample. This is inconvenient for many people, and we find that people never do it. They report only the tap water TDS and the DI water TDS. Contact Buckeye if you need guidance regarding installing a couple of extra fittings and tubing to facilitate measuring the TDS of the RO water (permeate). When you take the sample, follow the same procedure described above – use a clean sample container, assure you are not measuring TDS creep water, rinse with the permeate several times before taking the sample, and use a calibrated meter.

Use the same approach to collect and measure your tap water as well.

03/16/2009, 07:09 AM
Wow, Thanks for all the info. I hope you have this saved somewhere so you can just copy and paste. I am sure you get asked this stuff all the time.

Thanks again, and the new site looks great by the way.

Buckeye Hydro
03/16/2009, 04:49 PM
Thanks! All that info and more is available on our FAQ's Page (http://buckeyefieldsupply.com/faq.html)