tds meter question

[Delphinus]

I had actually been using my RO/DI directly to the float valves on my tanks and let them kick the solenoid on and off as required, but I found that I was exhausting RO membranes prematurely this way. At one point (you could even read about it here, there's a thread about it somewhere, I think from about a year ago) I went through 3 membranes in the space of a couple of months. So that's why I switched to filling up the reservoir, as needed, in one go (that's what was suggested to me anyhow). Maybe I should switch to a smaller reservoir - one that requires refilling slightly more often than the current 10 days it seems to offer me. Moving the float valve lower into the tank ought to do the trick.

[TheReefGeek]

I trigger my RODI once a day, I am still on my origital RO membranes, they are over 2 years old now, I haven't even flushed them out. I have gone through a few sets of the other filters & DI though.

My waste water production has probably increased, but I don't measure it so I don't know. Its probably time to replace my membranes.

[Delphinus]

At two years you might be getting close to needing to replace it. Then again maybe not. I think I got 3 years on my first membrane which is why I was so surprised at how finicky they can be after all.

Basically I wouldn't worry about replacing the RO membrane unless you get uncharacteristically high tds coming out. I.e., if you watch your tds then you'll know when it's time to replace it. I would get about 40-70 tds coming out which is still basically a tenfold reduction, so there was still function left, but still, obviously there's a problem if you get those kinds of numbers and not, say, 0 to 10.

I replace my prefilters approx. every 3 months.

[Delphinus]

Maybe when I come back from vacation I'll try a little experiment with a sprinkler solenoid valve, and just run the RO/DI every night for about an hour, and see what that does to the tds surge.

The only thing is I like running my reservoir empty between fills, that way I know I have water that's no more than "X" days old. I.e., if you run all time at near about the same level of water in the tank, then it becomes a pool of water that isn't completely refreshed periodically, and I can see that things like bacteria and whatnot could gain a possible foothold...

Sheesh - there is no end to the pros and cons of any idea, is there??

[TheReefGeek]

When you do a water change, you could use the reservoire water, then you know it is being 100% replaced.