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I'm getting .03 tds output from my ro/di unit. It's .03 in and .03 out. The rosin is still blue which makes me think it's still good. Should I change the rosin anyway or is there something else that could cause an above 0 reading ?

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I don't understand what you are measuring.

 

It's .03 out of the RO and also .03 out of the DI? If so then the DI is shot unless your TDS meter is flawed. What is the TDS of your tap water?



I'm getting .03 tds output from my ro/di unit. It's .03 in and .03 out. The rosin is still blue which makes me think it's still good. Should I change the rosin anyway or is there something else that could cause an above 0 reading ?

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I'm saying that the water going into the unit is measuering .03 tds and the water coming out of the unit is also measureing .03 tds. It's a before and after refference. There's no difference between the two. My tap water has .03 tds reading.

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All I can say is the water going in is .03tds as read by the tds meter. It's well water being drawn for more then 200 feet below the ground.

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Sounds like a bad TDS meter if the TDS is the same going in as it is coming out. Plus, it's highly unlikely that the TDS is .03 going in.

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Sounds like a bad TDS meter if the TDS is the same going in as it is coming out. Plus, it's highly unlikely that the TDS is .03 going in.

I also have a handheld tds meter. I'll try it . Thanks.

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AZDesertRat

Using the handheld TDS meter, what is your tap water TDS, RO only TDS before the DI and final RO/DI TDS? Always test directly from the tap or filter, not from a storage container or ATO if you are measuring the RO/DI condition.

 

Dual inline meters lack the accuracy of a good handheld mostly because they are not temperature compensated. The handheld should be your best friend. Never rely on color changing resins, most are very inaccurate and unreliable.

 

Also the meters do not read in decimals, most are whole numbers, what appears to be a decimal point is actually a power on indicator. The HM Digital COM-100 is one of the only handheld meters I know of that does and it only reads to tenths or 0.1, it is the meter I use and trust myself.

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Thanks for the info. The handheld meter read my tap water at 011 and water directly from unit read 000. The in-line meter agrees with the HH unit. Both have the same readings. You are correct about the decimal ,there is none.;)

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AZDesertRat

You are only giving two TDS readings, to troubleshoot a RO/DI system it requires 3 TDS readings. Tap water TDS, RO only TDS which is critical and final RO/DI TDS. Since the RO membrane is the workhorse of the system and does 90-98% of the work this reading is probably the most important one to have.

 

Using a squeaky clean, clear glass drinking water glass washed by hand in very hot water grab a sample of your tap water and insert the handheld meter, allow the meter to stabilize (this is important since TDS readings change with temperature and is why inlines and some lower end handhelds are not accurate since they do not have ATC correction) then write the reading down. Triple rinse the glass and the meter in RO/DI or distilled water then draw a sample of RO only water by disconnecting the line between the RO membrane and DI filter and again insert the meter, let it stabilize, write it down and do another triple rinse in RO/DI or distilled. Finally take a RO/DI sample, let it stabilize, write it down and do a final triple rinse, cap the meter so it stays clean and accurate and turn the glass upside down so it is clean for next use.

 

What are the three TDS readings?

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