A head scratcher

[reddrum]

So after several weeks of declining conditions in my tank (algae growth and general unhappiness of corals) I tested the ro/di water in my holding containers that I use for top offs and water changes. The TDS was 500! First thought was somehow the waste line got use to fill instead of the fill line. However, the waste line never leaves the drain and is labeled. I have a tds meter on both incoming and out going lines. It usually reads around 300 incoming and 000 outgoing. Also, nitrate and phosphate levels in the tank are at zero. I would expect that there would at least be measurable amounts if the waste line was being used. My containers are 5 gallon nalgene. Has anyone ever heard about nalgene leaching stuff back into the water? Ideas?

[FireWater]

Have you double checked your TDS meter on the R/O unit? Or are you using a hand held? Tried using a different bucket to hold top off to see if the problem is truely the nalgene material?

[CoryDude]

I'd double check both tds units for accuracy. I've found that a low battery can cause bad readings.

[reddrum]

I have switched the incoming and outgoing meters as well as used a separate handheld meter. The TDS meters are accurate. I have not tried storing the water in other containers yet since this was just discovered.

[Third Coast Tropical]

Barrett,
If it is the same nalgene container that I am thinking....I have never had any problems as you mentioned with the one I have, but it might not hurt to switch to another receptacle to see if it is the issue. How big are your water changes?

[reddrum]

Yes Lindsay I am sure they are the same ones you have. I am doing 5-10 gallon water changes. Today I am going to put some ro/di in another container and let it sit. Then retest it.

[Bill S]

Barrett, have you fooled with the membrane recently? In other words, are you SURE it's completely seated in the unit.

I'd guess you've either blown the membrane, or it's not seated fully/correctly. I remember Russ at Buckeye telling me that improperly seated membranes is his single largest issue.

BTW, when you test your source water (tap), what is the TDS?

Nalgene should never leach anything.

[CoryDude]

Forgot about this one. Have you checked the drain line to make sure it's not blocked? Had an issue with that where the drain line became plugged w/lime. Ended up having to replace the damaged tfc membrane.

[reddrum]

Unit is 2 months old. Drain line is flowing fine. If the membrane was blown then I should not get 000 readings out going. I even tried popping out the incoming meter that reads 300 normally and putting it in the outgoing water and it reads 000. So, I think the meters are accurate.

I have put LFS RO/DI in my container and I have put my RO/DI in a different container and I will test them after sitting overnight. I know measured TDS can increase with temperature but do ya'll think storing it in the garage could create a problem?