Replacing RODI filters?

[steri]

At what point do you replace RODI filters? I used my TDS meter this weekend and it tested out at 10 PPM. That seems very low, but it is higher than 0.

What do you think? The filters were last changed about 4 months ago (maybe 5), and that is when I bought the TDS meter. I figured I didn't want to change the filters just because, and wanted to make sure that the filters actually needed to be changed.

 

[melvinakshay]

Depends on how bad your inlet water quality is. Did you check the regular water ?

 

[steri]

When I first got the TDS meter I did. I seem to recall the tap water being around 60 if my memory is correct. I can check again tonight to be sure.

 

[xtlosx]

I use my color changing DI resin, and when it gets above 0, I replace the resin. When I can see visual discolorment in the sediment filter, I replace it. Carbon filter(s) change once or twice a year... The couple of bucks you'll save by not replacing them early and often for me personally, isn't worth the trouble of nuisance algae.

 

[ostrow]

Sediment every month.

Carbon every three.

DI when tds above 3.

Our systems are close enough in size that we must use similar water amounts.

 

[kawicivic]

Based on the ro/di websites, you shouldn't have to change your other filters that often. They say your pre-filters really only need to be changed when you notice a pressure change.

I use 2 dual TDS meters on my RO/DI to tell when to change filters. I also run dual di resins as well. The first TDS tests water going in - in my case low to mid 200s. The next one tests after RO - mine is normally under 10. This number will vary based on what kind of RO filter you have. That is what the percentage rating is for. If its a 90% filter then your reading should be 90% of what is going in. When winter gets here and my incoming water is super cold, I will usually get about 3 TDS out of the RO but the amount of waste is ridiculous. Finally, I test after each DI filter. The second DI filter is more of a backup for when the first is exhausted. I just installed the second TDS meter when I replaced my filters last and I have realized I was not changing my DI frequently enough. I also try to run to waste more frequently on startup as that is when my DI filters quite a bit more. Having a reading at each of these stages has really opened my eyes on how everything is working. I also installed a volume meter - that was also eye opening. I knew something was going on with my system in the winter and that was when I realized my waste water ratio was messed up and I did some research and found it was due to cold incoming water. Hot water will fry the membrane, but super cold lowers efficiency.

 

[kawicivic]

They recommend changing the pre-filters once a year I believe - I find it cheap insurance to change it more often.

I use these guys for filters and they have a pretty informative website:
http://www.airwaterice.com/category/18.filter_array/
http://www.airwaterice.com/category/z.5/

Here is a quote from their site:
When to change Filters and DI?
As mentioned before in our filters, membrane and DI FAQ pages, the filters need to be replaced when:
Pre-filters should be replaced at least annually. They include the 10 micron sediment filter, the 5 micron carbon block or catalytic carbon filter and the 1 micron carbon block filter (if one is installed).
>The sediment filter does tend to look like it's getting dirtier faster than the others. This is normal. Since it's the first filter, it's removing most of the heavy particulate matter. IF water production slows, see if it's the sediment filter first.
The RO membrane needs to be replaced every 3-5 years. If your water is hard and you do not have a softener, then you may need a larger flow restrictor. This is just a temporary measure and will only slow down the scaling process.*
The DI is based upon how well the RO removes TDS from the water.** Though we recommend replacing it at least annually, it may need to be changed more or less often. Go by TDS readings instead. If the TDS is above 5 ppm {stabilized), then you should replace the DI.

I am pretty sure they are a sponsor here as well. All of the sponsors that sell these filters are very helpful - the filter guys seems to search for RO/DI questions to help out people having issues.