TDS Meter and RO/DI

[RudyCDX1]

Greetings,

 

Two part question

[emissary]

I have an RO/DI unit producing my fresh water.  I purchased a TDS meter at the last meeting from Dr. Mac.  I have watched the meter readings begin to grow from .014 to now a reading of .028.  At what point should I take action on the RO/DI unit?

 

What should be changed on the RO/DI unit?  The DI?

 

What scale is this? My TDS meter measures in parts per million (ppm). I'm content when the PPM coming out of the filter is below 4 or so. But be careful to measure the water coming DIRECTLY from the output line. If you're using a resevoir, the tank you're using may have some contaminants that afffects the TDS testing. TDS testing should be done as "close to the source" as possible to answer the question "should I change my filter yet?"

 

How many stages is your filter? I used to have a cheapo Kent barebones filter that produced water at about 15ppm. Not great. Not terrible. Water from my brita is about 60ppm. Water from my tap is about 130 to 160ppm.

 

I now have a five stage (two DI stages because I'm lazy) filter that produces at 0 to 1 ppm. They're also color changing cartridges so I know when it's time to replace them. That is, unless there's a problem with the membrane. I honestly don't know how often to replace that. I replace my cartridges perhaps twice a year depending on what interesting things I've done that year.

[Grav]

All good advice.

 

I get 0 PPM and like it like that. 3 or 4 is no big deal, if that is what you consistantly get, but if you were getting 0 and suddenly you are at 4, it could be that the DI resin is going going going....

[RudyCDX1]

Thank you on the reply. I just checked the water directly out of the unit and my reading is 4. I must have some contamination in my container that is taking my reading up to 28. Thank you for the idea of the

[emissary]

Thank you on the reply.  I just checked the water directly out of the unit and my reading is 4.  I must have some contamination in my container that is taking my reading up to 28.  Thank you for the idea of the

[OUsnakebyte]

To extend the lives of your sediment cartridges until you order new ones, can you soak them in something? Is it vinegar...? I seem to remember reading that somewhere.

 

Then you throw out the next 5 gallons made, or something like that...? Am I totally out of it today?

[xeon]

As ongoing maintenance, it is a good idea to back flush the RO membrane. This will help extend the life of the RO. The filters you should replace more than anything else will be your sediment and carbon cartridges. If you have a pressure gauge on your unit and you see it dropping, that can be a sign the sediment filter needs replacing... plus you can visually inspect it. (Provided the housing is clear)

 

Putting a time on length on their life is tough to do since it depends a lot on how much water you run through them and the quality of the water to begin with. Replacing them (carbon and/or sediment) when they are nearing the end of their life will extend the life of the both the RO and DI. A used up carbon filter will do little to chlorine, which will wreak havoc on your RO membrane. If you want to take an extra step, you could also test the waste water for chlorine/chloramine in addition to regular TDS readings.

 

I don't know what is really "acceptable", but I try to keep my TDS as low and close to zero as I can.