How are you removing chlorine/chloramine?

[Buckeye Hydro]

For those with spot-free rinse, how are you removing chlorine or chloramine from your municipal water before it reaches your RO membranes?

Backwashing carbon tank?
Non-backwashing carbon tank?
Carbon block cartridge(s)?

 

[Greg Pack]

Backwashing tank at one, non-backwashing tank at another. The one without a backwashing head seems to work just fine and the membranes last several years.

 

[Buckeye Hydro]

With non-backwashing carbon tanks, best to have either really low sediment levels in the feedwater, or put an appropriately-sized sediment filter ahead of the tank.

Have you tested the effluent for chlorine? FilmTec membranes (for instance) can handle exposure to free chlorine up to 200 to 1000 ppm hours.

 

[Greg Pack]

I haven't checked. Usually when my TDS rises I change both the membranes and carbon. It's not very often, every three years or so maybe. When I replace the tank (20 years old) I have considered buying a backwashing head.

 

[Buckeye Hydro]

At least in your backwashing tank you should be getting 5 years of life out of your carbon. The life span of the carbon in the non backwashing tank is another thing. That carbon bed never get reclassified or mixed/shuffled (as happens during backwash) so its likely the carbon that gets hit first by incoming water exhausts first. Because the tank doesn't backwash you have the additional concern of it clogging with sediment/particulates. Yes - a backwashing tank/valve is a much better set up. It's good practice to plumb in a sample port after the carbon tank (or any treatment equipment) where you could sample the water for the presence of chlorine/chloramine.

Membrane life is independent of the carbon life span, and can be very short (weeks in the absence of proper pretreatment) to a few years (2+ yrs not uncommon).

Another thing we've seen at some of our maintenance sites is incorrectly sized carbon tanks. The bigger the tank the more carbon can be used and the higher flows it can handle (as long as you have adequate feedwater flow for the backwash). If your water utility uses chloramine (chlorine + ammonia) rather than chlorine as a disinfectant, you'll want to use a different media (catalytic carbon) and size the tank for a longer contact time. The last I read about a third of the country is on municipal water with chloramine.

Russ

 

[Scott220]

I’m using a propak H100 (13” GAC 2CF) backwash filter. The carbon needs changed. is there a certain type carbon I need and how many pounds?

 

[DakotaHoskins]

We have chloramine at a busy site and we had to upgrade the 4 ft carbon tank to a 10ft carbon tank when the city made this switch. We were using 4 new membranes every 4 months. Now they are lasting over a year again.

 

[Buckeye Hydro]

Can't say I'm familiar with that particular model, but it's probably a 13" x 54" tank. Total volume of that tank is about 3.7 cuft and it's typically loaded with up to 2.5 cuft of carbon. https://www.buckeyehydro.com/gac-granular-activated-carbon-1-cuft/

So first, talk to your water utility and see what disinfectant they use - will either be 1) chlorine, or 2) chloramine.

That info will affect what kind of media you reload it with.

What diameter pipe feeds it? Does it supply an RO unit only, or does it feed other outlets as well?

You'll buy replacement media by the cuft rather than by the pound. Each cuft bag weighs about 27 lbs. https://www.buckeyehydro.com/cgac-catalytic-granular-activated-carbon-1-cuft/

You'll also want 30 lbs of #20 underbedding. It is possible to save the gravel when you empty to tank, but because the underbedding is so inexpensive most people don't mess with trying to save it.

 

[Buckeye Hydro]

We have chloramine at a busy site and we had to upgrade the 4 ft carbon tank to a 10ft carbon tank when the city made this switch. We were using 4 new membranes every 4 months. Now they are lasting over a year again.

Yep - chloramine will prompt use of a different media in the tanks, use of larger tanks (like your 24" x 72" or larger tank) and more media to get longer contact times.

Chloramine = Chlorine + ammonia