Chlorine questions

[ostrow]

Hi Randy:

I have been suffering slow speed die-off/regrowth swings for over a year with zero net growth. Weird. I test my levels regularly and all is normal in terms of ca/alk/mg/sg/ph/temp. Replace halide bulbs on schedule. Anyway...

As for about 3-4 yrs I have had only 12-18 month lifespan on my Dow 75gpd ro membrane I decided to test for chlorine /chloramine. I live near Chicago and the water here is not particularly high TDS from the tap (172 or so) and my town does not add chloramine they say but still.

So my tests:

"Total chlorine" measured 0. "Free chlorine" measured 1.4/5 = about 0.3 using a Hach CN-70 kit.

I tested the water post-carbon (2 1-micron blocks) going into the membrane.

Do you have a good explanation of total vs free carbon and whether this level is something I must address. And how?

I am kind of grasping but well...

Thanks.

 

[Randy Holmes-Farley Verified Community Expert]

Likely test error. Total chlorine is always equal or higher than free chlorine. But the kits may not have equal sensitivity. In general, chlorine very rarely gets through an Ro/DI if the carbon block is reasonably new.

 

[ostrow]

Thanks.

That level going in (assuming the free test was correct) won't rapidly destroy a membrane?

 

[Randy Holmes-Farley Verified Community Expert]

Going in after the carbon block?

 

[BlueCursor]

For water exiting an RO, check TDS. If your carbon blocks are shot, chlorine will destroy your RO membrane and your TDS will go up pretty quickly.

A 12-18 month lifespan on my Dow 75gpd isn't unreasonable if you are producing lots of RO. I know if I get lazy on changing my carbon blocks every 6 months my RO membrane doesn't last nearly as long as it should.

FWIW, I would get a PAR meter and check how much light your corals are actually getting. It sounds more like low light than a chlorine issue, unless your fish are doing poorly too.

 

[Brew12]

I'm not suggesting that I think chlorine is causing you a problem, but if it is something you are worried about you can add a carbon block filter before your RODI system for about $40 in parts from BRS.

 

[ostrow]

Randy: yes, after my 2 carbon blocks (I believe these are from Air Water Ice). They are both less than 6mks old. One is 3 weeks old the other 3 months.

Which should address the other posts above (not the par but I know this is not an issue).

 

[Randy Holmes-Farley Verified Community Expert]

I don't think it likely that chlorine is getting through two carbon blocks, especially if one is 3 weeks old.