TDS in Auto Top Off reservoir is 333!

Reece · Sep 27, 2018

Hello,

So I was calibrating my tds meter and I wanted to make sure my RO/DI water was sitting below 5 which it was. I have just recently transferred my old reef tank to a new Aqua one reef 180. The sump has a reservoir for top of water. I filled the section up last night and this morning for what ever reason I tested it with the tds meter and it reads 333. Is this normal due to evaporation with in the sump area or is something not right. I know the reservoir seals are okay because it was left empty for a while whilst I set everything else up and before filling it with Ro I made sure to give it a good clean.

I have never had this problem before as I have always toped off from a barell.

I was doubting myself that maybe I used the wrong barell to fill it up so I went out and tested the water from the same barell and the tds for that batch is 3... would be grateful for anyone's input. TIA

Retro Reefer · Sep 27, 2018

Either the reservoir was dirty when you filled it or it’s leaching contaminants into water.

pwilliaml · Sep 27, 2018

Is the tank / reservoir brand new? If you didn't clean it out with DI water, it may still have some residual chemicals on it from the machining process that were absorbed into the water. Either way, empty it, clean it all out with DI water and set it back up and check it again after a few hours to see if the TDS slowly creeps back up.

miPapareef · Sep 27, 2018

Salt creep. Either in there before you filled or it’s getting some splash after you filled.

ajm83 · Sep 27, 2018

I had this when I had a tiny bit of back flow from the sump to the ATO chamber.

Why is your RO/DI TDS reading so high though?

Reece · Sep 29, 2018

Okay so thanks for the suggestions. I emptied the reservoir, dried it and left it for 12 hours to check for any tiny leaks, there were none. Have rinsed out with di multiple times and have filed the chamber back up. Will test tds in an hour and in the morning... hoping for no change.

Randy Holmes-Farley · Sep 29, 2018

As little salt spray landing on it will do it. The reef tank water itself is on the order of 50,000 ppm TDS, so it doesn't take much to give an effect.

Reece · Oct 2, 2018

Randy Holmes-Farley said:
As little salt spray landing on it will do it. The reef tank water itself is on the order of 50,000 ppm TDS, so it doesn't take much to give an effect.

I think you are on the money. I left the doors open and left for a few hours and measured the tds... was reading 3/4 and then closed it and left it over night. What would you know slowly creeping up again. At least now I know. I was worried there was something in the silicone or a small leak but it's just one of many questions answered for now. Thank you