Jump to content

RO / DI Replacement filters


Recommended Posts

Which sponsors sell filter stuff for a kent marine hi s di filter?


I think the sediment filter and carbon filter are pretty universal so i'd like to know who carries just these because they get replaced most often.


Lastly how often are replacing their filters here? (especially anyone using a silicate remover)


I found this on another forum so I thought I would share


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 its 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!

Link to comment
Share on other sites

So far after new filters and di resin I am getting 0 ppm outgoing' date=' in Gresham the water is between 16 to 20 ppm.[/quote']


Portland is obviously very similar..its about 15ppm from the tap for me.


I use a dual in-line tds meter. I generally change my resin when it starts changing color, but sometimes the TDS goes up to 1ppm before it looks like the resin is "used up". The meter definitely helps a lot in this situation.


Personally, I don't use RO. I just use a carbon filter to remove the chloramine, then a DI filter to remove everything else. I consistently have 0 TDS after the DI filter. I don't think you can get away with this if your TDS from the tap is in the 100's though...

Link to comment
Share on other sites

One thing different between the water sources of vancouver and portland is portland is bull run water and vaccouver water comes from wells. I have checked my water for TDS in vacouver and found between 103-140 over the last 3 years. Vancouver water also has between 9-10ppm of nitrates out of the tap. Most people didn't realize that...

Link to comment
Share on other sites

Anyone know if there is much silicates in Portland water?


Portland drinking water report can be seen here:



It does not appear to have silicates in the water...


Most major cities post their drinking water reports online. It's a nifty way to see what exactly is in your water without doing a bazillion tests.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...