WHEN to change RO/DI membrane and DI cartridges

[blackstallion]

As the subject suggests, looking for guidance on whether it's necessary to change out the membrane and DI cartridges on a regular basis, ie. yearly, OR, is it based off of TDS coming out?

I have a 90gph Spectrapure 5 stage system, been running for about 2 years on the original membrane and DI cartridges. I have swapped out the pre-filter and carbon filter.

Right now, TDS out is still 0 (coming in anywhere from 60-90), although water production rate is down from what it used to be, which doesn't bother me to much.

Would there be any reason I need to consider changing out the DI cartridges or Membrane?

 

[Spare time]

Membrane: When the TDS outgoing starts going up a lot

DI Resing: when TDS is greater than 0

Carbon: when (hach) chlorine strips detect chlorine. I sometimes swap this out with sediment filter


Sediment: When the psi drops below 60 or so

 

[Spare time]

Have you calibrated the TDS meter? The water going in has a pretty low TDS which is interesting, so maybe that's why the di resin is still working

 

[mfinn]

I change the membrane when the TDS goes from a normal 2-3 up to 4-5. ( It's been a couple years now and it's still come out at 2-3.
I change my di when it shows 1. I have a dual di system so if I'm making water and I notice it at 1, I'll continue until I've made all the water for that period. Then I'll switch the di around and replace the one that was showing any tds.

 

[Jeeperz]

I'm on year 4 of my spectrapure ro membranes. I have the megamax cap 180 gpd unit. I change sediment/carbon yearly. 2 years on di but that was due to do being made at the end of their batch and it was difficult to push through it, spectrapure sent me new di that fixed it. I do have to degas my ro before pushing it through the di though. I'm going to replace all filters first of the year just because. I make between 40-80+ gallons of rodi each week just for a reference. My incoming water is between 80-90 tds, ro roughly 0-1, di 0

 

[Uncle99]

As the subject suggests, looking for guidance on whether it's necessary to change out the membrane and DI cartridges on a regular basis, ie. yearly, OR, is it based off of TDS coming out?

I have a 90gph Spectrapure 5 stage system, been running for about 2 years on the original membrane and DI cartridges. I have swapped out the pre-filter and carbon filter.

Right now, TDS out is still 0 (coming in anywhere from 60-90), although water production rate is down from what it used to be, which doesn't bother me to much.

Would there be any reason I need to consider changing out the DI cartridges or Membrane?

No reason at all if the end result is zero and your not eating up DI super fast.
Zero TDS is Zero TDS…..fix only what’s broken.
Carbon and sediment cheap so those I do at 6 months.

 

[Buckeye Hydro]

This is copied from our FAQ's:
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. 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

 

[Big E]

This is copied from our FAQ's:
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. 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.

Any suggestions on good pressure gauges that last. I've tried the liquid & dry and they crap out in less than a year.

Is one brand better than others?

 

[Buckeye Hydro]

HI Russ.

Any suggestions on good pressure gauges that last. I've tried the liquid & dry and they crap out in less than a year.

Is one brand better than others?

Hmmmm. We've not had anything but very rare issues with the pressure gauges we stock. There are so many manufacturers....

What happens when your gauges fail?

 

[mnl119]

Right now, TDS out is still 0 (coming in anywhere from 60-90), although water production rate is down from what it used to be, which doesn't bother me to much.

Have you tried flushing out the membrane housing? This might restore the original flow rate.

 

[Jason_MrFrags]

When the psi drops or the tds out of the membrane starts to rise. Keeping the prefilters changed will extend the life of your membrane. Also flushing the membrane after you are done making water will also help.

 

[Big E]

Hmmmm. We've not had anything but very rare issues with the pressure gauges we stock. There are so many manufacturers....

What happens when your gauges fail

It's just reads zero..........no pressure showing when the unit is on making RO water.

 

[Buckeye Hydro]

It's just reads zero..........no pressure showing when the unit is on making RO water.

Feel free to give us a call - you need a new pressure gauge.