Should I change my RODI filters if water is 0 ppm?

[Neto]

Its time to change my RODI filters, I usually change them every 6-9 months but it has been 9 months and my TDS meter reads as follows:

 

RODI: 0 ppm

RO: 6 ppm

Tap water: 277 ppm

 

I did calibrate the tds meter (tds-ez) with the 342ppm solution and all the readings where on a small clean glass jar.

 

So the question is, should I change these filters even though the readings look good? 

[YHSublime]

Should you change your oil every 3 months if you haven't driven 3000 miles? 

 

I wouldn't, but I usually use synthetic and change it after 3k regardless, not time wise. If you've still been making consistent water on it, and it's not done, then why would you? What I would do is have filters on hand, and test every couple of weeks, JMO. 

[WheresTheReef]

The recommendations for changing will vary based on how much water you produce. Seems like your filters are still good based on your numbers.

 

This might be useful.

https://www.bulkreefsupply.com/video/view/howto-know-when-to-change-your-rodi-filters/

[Jon Lazar]

The sediment filter's purpose is to protect the carbon filter from getting gummed up.  The chlorine block's purpose is to protect the RO membrane by removing chlorine (and maybe chloramines) which damage the RO membrane.  That's their real purpose: protecting and extending the life of the RO membrane.

 

If the carbon block is exhausted or clogged, you'll damage your RO membrane.  Maybe then you'll see increased TDS, or maybe you'll just lose RO production.  

 

The bottom line is you can't wait until you see increased TDS.  You need to change the sediment filter and carbon block when they're nearing exhaustion.  I think most folks guesstimate when the filters are about used up and change them, rather than risk damage to the (more expensive) RO membrane. 

[Origami]

The sediment filter's purpose is to protect the carbon filter from getting gummed up.  The chlorine block's purpose is to protect the RO membrane by removing chlorine (and maybe chloramines) which damage the RO membrane.  That's their real purpose: protecting and extending the life of the RO membrane.

 

If the carbon block is exhausted or clogged, you'll damage your RO membrane.  Maybe then you'll see increased TDS, or maybe you'll just lose RO production.  

 

The bottom line is you can't wait until you see increased TDS.  You need to change the sediment filter and carbon block when they're nearing exhaustion.  I think most folks guesstimate when the filters are about used up and change them, rather than risk damage to the (more expensive) RO membrane. 

+1 to this.

 

Your sediment and carbon filters are the cheapest insurance that you have on water quality and RO/DI production efficiency. Putting them on a regular schedule makes good economic sense.

[Neto]

Thanks folks

[zygote2k]

the old rule of thumb was to change filters when the TDS "out" is greater than 10% of TDS "in".

[Origami]

the old rule of thumb was to change filters when the TDS "out" is greater than 10% of TDS "in".

Note: This rule would not apply to your front end filters. Rather, it's more applicable to monitoring the efficiency of the RO membrane (that is, comparing TDS in and out of the membrane - not out of the DI stage) to determine when to change that stage out. I would contend, however, that letting your RO membrane get that bad would be preceded by a rather expensive period of DI resin quickly exhausting (assuming that dissolved CO2 wasn't already causing that problem). Instead, I would keep a log of how the system is performing and when you make changes. Change the front end on a schedule - maybe every 6 months or so for the inexpensive front end filters. They are there to protect the more expensive RO membrane which is there to clean up the water as much as it can before it reaches the DI stage. Monitor the long term TDS in/out of a membrane to see when it's efficiency falls off and to monitor the time between DI resin replacement to figure out when the RO membrane is degrading. 

 

Using this approach, back in my old Ashburn home (which was on municipal water, unlike the well that I'm on now), I was able to sometimes get 9 months out of my DI resin stage before it needed replacement. (I had something like 180 ppm coming in and 2 ppm coming out of the membrane.)

 

I would say that your DI membrane is still performing fine. Depending upon the make/model/speciication of that membrane, you're getting 98% rejection which is very good.

[YHSublime]

This is all great information, thanks for starting this!

 

 

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