When to Proactively Change RODI filters

[PeterC99]

New member to R2R and looking for advice to proactively change RODI filters. Have Red Sea Reefer 170 for 6 months. Change 5 gallons with fresh RODI saltwater every week. Corals and fish doing very well. Just bought used 425 XL and starting process of setting up and cycling. Really enjoying this hobby!

Back to RODI filter changes. Do you recommend scheduled changes (e.g., every year), when TDS output is no longer zero, sudden changes in tank parameters, or something else?

Appreciate any guidance or feedback.

Thanks!

 

[pdxmonkeyboy]

I change the prefilfers as soon as they are light brown. I learned the hard way that when they get too dirty sediment can pass and clog the RO membrane.

I also flush the membrane before making RO. That helps keep the membrane clean.

Once TDS gets to like 3 i replace the membrane.

 

[piranhaman00]

I change the prefilfers as soon as they are light brown. I learned the hard way that when they get too dirty sediment can pass and clog the RO membrane.

I also flush the membrane before making RO. That helps keep the membrane clean.

Once TDS gets to like 3 i replace the membrane.

Sediment should never pass the sediment cart. When it gets clogged you will see your PSI drop. The more clogged the less sediment getting through actually.

 

[Finnaddict]

I change the sediment when it gets brown or my pressure drops. Carbon are changed every 8 -12 months and RO membrane every 3-5 years. All depends on how much water you make. Resins are changed when color changes or I see a 1-2 TDS coming out.

 

[mike550]

I think the suggestions I've seen are to swap pre-filters when the water pressure drops. I use a color changing resin for the DI stage. And the membrane is once every three years. That said, I try to track the amount of water I produce and then I change the carbon block and sediment filters around 60-70% of estimated lifetime of the carbon block since that occurs before my sediment filters start to reach capacity.

 

[pdxmonkeyboy]

Sediment should never pass the sediment cart. When it gets clogged you will see your PSI drop. The more clogged the less sediment getting through actually.

Not when you have a 95 PSI pump pushing it. The water WILL find a way to bypass around the sediment filter and I have the filthy RO membrane to prove it.

 

[piranhaman00]

Not when you have a 95 PSI pump pushing it. The water WILL find a way to bypass around the sediment filter and I have the filthy RO membrane to prove it.

Oh yes that does make sense with a booster pump

 

[pdxmonkeyboy]

Yeah, I thought the same thing. A clogged filter is actually a better filter. But my production dropped off big time, pulled the RO membrane out and cut it open... Well, won't do that again

 

[Reef.]

The booster pump should be after the prefilters, this way no sediment is going into the booster pump, it also helps protect the seals etc on the containers.

 

[chipmunkofdoom2]

If you're changing filters proactively, change the prefilters every 6 months, the membrane every 2 - 3 years, and the DI resin when your TDS reads above zero. That's pretty wasteful though. With basic testing you can tell exactly when specific filters in your system need to be replaced. I've been on my current prefilters for 2+ years and used my last RO membrane for 10+ years.

The sediment filter needs to be replaced when pressure drops over the prefilters. To measure this, put a pressure gauge before the prefilters and another after the prefilters. When the pressure drops significantly*, the prefilter is clogged and needs to be replaced. If replacing the prefilter doesn't raise the pressure, your prefilter may have been too big and your carbon blocks may be clogged. They might need to be replaced too.

The carbon blocks need to be replaced when they can no longer process chlorine/chloramines. To test this, measure chlorine using test strips in the brine (waste water). If the reading is anything above zero, your carbon blocks need to be replaced.

The membrane needs to be replaced when the rejection rate drops too low. To measure the rejection rate, test the TDS before the membrane and after. Divide the "after" number by the "before" number. The membrane should remove 95%** or more of the solids from the water. If the number you calculated is higher than 0.05**, the membrane needs to be replaced.

DI resin should be replaced when TDS is above zero. This is pretty important since weakly-charged ions will begin to detach from DI resin as the resin exhausts. As a result, your DI resin can actually release compounds like ammonia in bulk as it gets close to the end of its useful life.

* What significantly means will vary to you, but I try not to let mine go for more than 5 - 10 PSI. It all depends what your source PSI is.

** this number depends on your preferences and setup. You may not have 98%+ rejection if you have low pressure. Also, you might not want to replace the membrane the second the rejection rate drops a single percent. So, I chose 95% as the threshold. Choose whatever number works best for you.

 

[PeterC99]

Thank you - didn't occur to me to test the individual components but will going forward. Definitely more economical and environmentally friendly (not getting rid of filters before they are exhausted and tossing into the garbage/landfills).

 

[ichthyogeek]

So, the carbon filters actually have a rating for how much chlorine/chloramine they can take out:


And the DI resin is supposed to be changed out when it's changed color to an inch from the top. The most economical way, would be to buy the anion and cation resins separately, and recharge as needed, since most households tend to have an excess of one or the other.

As for the sediment filter, I change it when the carbon filter needs to be changed.

 

[homer1475]

I change my prefilters when I change my DI, or when TDS is above 0. Seems to work out just about right for me. Pressure starts dropping right about the same time my DI is shot(I get 1 TDS out of my membrane pre DI).

Just the way I've always done it wasteful or not.