How often do you change RODI filters

[jeflen651]

Hey everybody, how often do you change your rodi filters? I only make about 40 gallons per month and I have not seen much of a pressure drop. Starting to see a little bit of color on the white polishers at the bottom. My tds are nearly "0". In the past I have been changing them yearly. I was just wondering what others do.

 

[bif24701]

Get BRS total chlorine test strips. When you start detecting more chlorine in the waste water it's time to change the carbon. When pressure drops to your RO from normal, change sediment. Change the DI when your TDS rises in the good water. RO membranes should last you many years if you maintain it, flush them, and keep chlorine away from them because it will oxidize them.

 

[ALs FLorida Corals]

once the tds goes up I change the expensive folters.once he sediment one turns brown I change it . that's only 3 bucks

 

[cromag27]

Here's the lowdown on rodi....

First, inline tds meters are not accurate. I use a handheld - hm digital com-100.

Membrane - change when rejection rate gets down to 96%, or you experience a decrease in psi.
Sediment - change at 6 months or if psi decreases, whichever comes first.
Carbon - change at 6 months or if detectable chlorine, whichever comes first.
Di - change when tds reaches 1

If you use dual di like spectrapure, then maxcap di get changed at a different interval and final stage di gets changed when tds reaches 1.

 

[Viracon13]

I just received my order of BRS RODI filters today. I change them once I notice my output decrease. In my case, this was 10 months. I probably make 50-60 gallons a month

 

[4FordFamily]

Not nearly frequently enough... I make A LOT of water and need to change them more with my really hard water :/

 

[NanaReefer]

My tap water has a TDS of 165. My filters last quite a while. My DI Resin lasts almost a year [emoji2] I make a little over 60g a month.

 

[bif24701]

Bottom line is all water is different and you filter life will be different.

When to change:
Sediment: pressure drops by +5%
Carbon: chloramines/chlorine is detected in waste water
RO: rejection rate falls +2%
DI: TDS detectable

Test and monitor. That how to know if your filters need changing.

My system is 300 gallons and I make hundreds of gallons a month. I changed my sediment and carbon filters @ 8 months, because I found them to be exhausted. RO membranes can last years and years.

If you run through DI fast you could have a lot of dissolved CO2 in your water. Collect water before going through the DI, use and air stone to get the CO2 has out then pump it through your DI.

Test and monitor.

 

[jeflen651]

Thanks to all who have commented. Very much appreciated.

 

[don_chuwish]

So my input pressure is showing 74psi before sediment, carbon x 2, then 69psi before RO membrane. Is that low enough to change carbon? Sediment filter is barely off white - the water here is very clean. Handheld TDI meter shows 38-40 tops.

 

[Buckeye Hydro]

Here's a cut/paste from our FAQ's section - you can access all of our FAQ's from our homepage:

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 more of the prefilters (all the filters that touch the water before it reaches the RO membrane) 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 much of the 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. Remember that all the water you process, both waste water and purified water, goes through the carbon block. It's good practice to change the carbon block out at no more than 50% of the stated chlorine capacity.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 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 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 membrane 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 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an 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 TDS in the water coming into 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 purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS 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.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ

 

[don_chuwish]

Thanks Russ, that's a great read!

 

[revhtree]

Get BRS total chlorine test strips. When you start detecting more chlorine in the waste water it's time to change the carbon. When pressure drops to your RO from normal, change sediment. Change the DI when your TDS rises in the good water. RO membranes should last you many years if you maintain it, flush them, and keep chlorine away from them because it will oxidize them.

Very helpful, simple and to the point!

 

[Larry L]

All good comments above, a couple things to add:

Get BRS total chlorine test strips. When you start detecting more chlorine in the waste water it's time to change the carbon.

I try to test for chlorine as close as possible to where it comes out of the prefilter. If your unit has a "DI bypass" that helps, or you can splice in a tee and ball valve just after the prefilter to make it easy to take a sample there.

track the TDS ... in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

This is easy if you use inline TDS meters with multiple ports, I've seen them with either two or three ports. My setup has two DI canisters, so in addition to those three places that Russ mentioned, I also have a TDS port in between the two DI canisters. When the numbers coming out of the first DI go up too much compared to what's coming out of the RO membrane, I swap the second DI canister to become the new first canister, and put fresh resin in what's now the second canister.

 

[Jizu Puentes]

I change my prefilters every 6 months and DI whenever it reaches 1 TDS. My setup is one sediment filter of transitioning microns then a carbon then RO then DI.

 

[Klaas]

Here's a cut/paste from our FAQ's section - you can access all of our FAQ's from our homepage:

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 more of the prefilters (all the filters that touch the water before it reaches the RO membrane) 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 much of the 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. Remember that all the water you process, both waste water and purified water, goes through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 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 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 membrane 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 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an 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 TDS in the water coming into 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 purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS 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.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ

Hi Russ. Thanks for the extensive information. As for DI resin would we need to use Anion or Cation resin or a combination of the 2? I can buy those in bulk here in Manila. Thanks for your help. Cheers. Klaas

 

[BMan]

Great thread. I just set up a used Maxxima HI-S last night and was wondering the same questions. The waste stream seem to be about the same flow rate as the product flow rate. Is this normal ?

 

[jwshiver]

Additionally, don’t forget to sanitize the entire system at least once per year,

I have never heard of this. Is there a standard procedure for this or a link you can provide?
Thanks.

 

[West1]

Great thread as when to replace was just on my mind.
Can you guys specify which replacement filters you use?

 

[gary henkel]

Great thread as when to replace was just on my mind.
Can you guys specify which replacement filters you use?

i find my di needs to be changed about every 3 months. if tds is not zero, it gets changed. one caveat. membrane life can be greatly increased by regular backwashing of the membrane. i use the aquatic life smart buddy booster pump with my filter. not only boosts pressure for better yield but does an 18 second backwash every time it starts up.

gary