RODI - When to change filters?

[mattevo]

The replacement filter kits don’t typically come with this part. How often does this part need to be changed?

I’m getting 15 TDS before the DI and 0 after. That sound right? Would you ever change just some filters based on TDS readings or just change them all at the same time every time?

 

[Woodyman]

https://www.reef2reef.com/threads/ro-di-basic-guide.886770/post-9807561
This should give you detailed help!


15 may be normal or not, do you have any idea what your source TDS is? The only real way to tell when replacement is necessary is to do some math, even then replacement is arbitrary it's all about your comfort level and how often you want to replace the more expensive DI cartridges.

 

[JumboShrimp]

So many factors can be at play. I have the 7-stage BRS system; 5 canisters, two membranes. I exchanged the two membranes after about 4-5 years, and they were both still clean as whistles. That is just to say, generally speaking, if all of the parts of your system are working properly and being changed fairly regularly, that membrane you have in the photo should be good for at least three years or more, minimum. Just my 2-cents there. Hope that helps!

 

[Woodyman]

So many factors can be at play. I have the 6-stage BRS system; 4 canisters, two membranes. I exchanged the two membranes after about 4-5 years, and they were both still clean as whistles. That is just to say, generally speaking, if all of the parts of your system are working properly and being changed fairly regularly, that membrane you have in the photo should be good for at least three years or more, minimum. Just my 2-cents there. Hope that helps!

Indeed, 3-5 is probably a good general number for those that don't monitor rejection %. It's also not all about the number either. Some source water is harder on membranes, one person's 100 TDS source and someone else's may treat those membranes totally different. Leading one to start fouling after a year or less.

 

[JumboShrimp]

(Also I back-flush for a couple of minutes after each fill session; you can buy the flush valve and add it if you don't have it.)

 

[Woodyman]

Back flushing and pressure are your friends here with membranes!!

 

[JumboShrimp]

(Good point; I also have a booster pump.)

 

[Woodyman]

Makes a difference!!

 

[Luisn17]

Florida water, I get 1-2 TDS after the two membranes, then 0 and 0 after the DI units. I swap them once I see a 1. I have BRS 7 stage, water saver unit with pump booster and auto flush.