Time to change my RODI filters / membrane?

[offshored]

I've had my RODI system up for about 6 months and have probably made ~ 200 gallons of RODI water with it.

I see my filters say 6 months or 3000 gallons, so since it's been 6 months and I haven't even passed 10% volume through the system... is it time to replace them?

Also, should I replace the membrane and final filter as well? Or just the carbons and sediments?

I've seen a little bit of a brown diatom build up, so that's what's sparking my question. Turbos are taking care of it, but still :debi:

Thanks guys :thumbsup:

[GSMguy]

Replace the DI and first stage at the minimum. I usually replace everything, but the RO membrane. The membrane is good for two years.

[offshored]

Thanks Nick!

I am about to start filling up my 240 this month, so I want to make sure the water going in is good.

The filters are dirty cheap, good thing I can hold off on the membrane for a while :)

When the annual pack of filters is up, I'll get a pack with a membrane, so 1 1/2 years on the membrane.

[GSMguy]

Sounds like a good plan. I recently changed my DI and prefilters and my TDS coming out of the membrane went from 8 to 3. Which means this DI will last me longer than the last.

[DHyslop]

Without a TDS meter there is no reliable way to monitor the performance of the system and determine an effective replacement strategy. Using color change resin can be helpful for the DI stage but still leaves you clueless about how the RO membrane is performing.

[Buckeye Hydro]

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable 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. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some 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 dependent 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, 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 than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Russ

[GSMguy]

Russ i am on a well, my prefilters start to yellow at 5 months but I have no chlorine obviously. Should I replace my carbon blocks less frequently than the current every 6 months?

[catfish]

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable 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. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some 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 dependent 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, 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 than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Russ

What he said

[Buckeye Hydro]

Russ i am on a well, my prefilters start to yellow at 5 months but I have no chlorine obviously. Should I replace my carbon blocks less frequently than the current every 6 months?

First, because your water isn't chlorinated, I wouldn't use a carbon block any better than a 5 micron. Can you go longer than 6 months? Probably. How much longer? Hard to say. I wouldn't go more than 9 months. Remember your entire system is bathed in non-chlorinated water, and is prone to microbial growth. So if you see any evidence of this when you change your prefilters, I'd stick to 6 months. Also - you should be sanitizing your system at least once /yr.

Russ

[crackedcorn]

What is the best way to sanitize the ro di system?

[Buckeye Hydro]

http://i224.photobucket.com/albums/dd293/BuckeyeFS/Sanitize.jpg

Russ

[Landsailor]

That's great advice, Russ. Is the squirt of hydrogen peroxide in a pressure tank sufficient or do you have a better idea?

I'm doing the RO/DI presentation for our club in November. Mind if I steal that pic? I also want to pick your brain about some water saving ideas from other vendors. :)

[Buckeye Hydro]

We have some different instructions for systems with pressure tanks. Drop us a pm with your email and we'll send it to you.

OK by us if you use those instructions as long as you keep our logo and copyright message on there.

Be happy to talk with you re prep for your presentation. There may be other graphics we can provide if you are doing a powerpoint.

Russ

[asylumdown]

Russ i am on a well, my prefilters start to yellow at 5 months but I have no chlorine obviously. Should I replace my carbon blocks less frequently than the current every 6 months?

Wow, well water and you get 5 months out of your pre-filters? That's great. I'm on city of Calgary tap water, and my pre-filters are dark orange after 2 months if I don't change them, and we're supposed to have some of the best drinking water in the world. Makes me squeamish about drinking normal tap water.

[Buckeye Hydro]

Wow, well water and you get 5 months out of your pre-filters? That's great. I'm on city of Calgary tap water, and my pre-filters are dark orange after 2 months if I don't change them, and we're supposed to have some of the best drinking water in the world. Makes me squeamish about drinking normal tap water.

"orange" is often indicative of iron in the water