Need advice on TDS meter readings

[Brisc0]

Okay, so I am ordering from doc mac the other day and I see the TDS meter and figure... "whats another 30 bucks" so I open it up and test my RO/DI reservoir. Its 001ppm right now with 6 month old media. Im thinking "not so bad". Then I get a sample from the 30G top off container behind my tank to make sure its okay and it reads 015ppm. I will however admit that I have no sense of scale as to what this thing is telling me, and for all I know 015 ppm is nothing, but then again I might be dumping trash into my tank. Anyone who can enlighten me with links or personal experience is greatly appreciated.

Thanks everyone

[fishfreek]

Test your tap water and youll notice even 15 is rather low. Although I suspect your 15 measure on the top off container is a result of it not being covered or if it is covered possible contaminants like sand or dust getting into the water when you add to the container or tak away from the container.

[Brisc0]

I tested the tap water and its around 145ppm. The top off container is just a closed rubbermaid 30G with a maxi12 in there to keep it from getting stagnant. Do you think i need to consider the 015 as cause to pull the can and replace it, or is it a trivial reading?

[Phyl]

Never test out of plastic. Always test freshly poured RO/DI out of the unit into a glass container. The plastic leaches something into the water. Try that and post back your readings. That will happen with any plastic container. No need to discard the one you have!

[aquafreak]

Agreed with last post. My top-off H2O (RO/DI) is exposed to the air and oftentimes knat flies land in the container and cause the PPM to increase a point or 2 but nothing drastic.

[fishfreek]

TDS meters are insanly sensitive. If you dont have an absolutly clean cup that your testing your water in you will have the potental to get rouge readings. An example. If you let a cup sit exposed with the top up for 1 week and then get a clean cup that freshly been wiped clean. Add RO water direct into each and then test I bet you the cup thats been exposed to dust and dirt will have a higher TDS.

Tap water of 145 is fairly good. Are you on city water or well water? Either way it sounds like you have fairly good water to begin with. I have heard some folks tap water being over 300ppm's.

[Brisc0]

Okay, well you have all made me feel waaaaay more comfortable. Here I am an experience reef keeper and I fell for the oldest trick in the book... (got scared from a new gadget I didn't understand)

Are you on city water or well water?

City water here. You can see in the pic im attaching the large 30G trash can behind my sump/fuge. That is what I got the 015ppm reading out of. The 001ppm reading came straight out of the hose from my RO/DI.

Thanks again everyone, much appreciated help.

[seaham358]

If there is any chance that salt got into that can it will increase the TDS.
TDS total disolved solids, no way to tell if there good or bad. I used to run my ro/di till I hit a tds of 15+ before I changed out my di resin. I also know guys who change it out as soon as it hits 2-5. If your using a high grade trash can like a rubbermaid rough neck then I would not worry about any leaching into the water. These are food grade cans from what I under stand so there should be no leach back.
If the can is close to the tank it is possible to get spray from the tank and if there is any salt in the can it will measure on the tds meter.

[Brisc0]

Update!

I use a vaccum pump to bring that water from the can to the tank when the float switch kicks on. This pump uses small airpump type tubing. I stuck a fresh clean tube on the pump and it lowered the readings to like 5 LoL. I am using a 32G roughneck btw.