Join Date: Nov 2008
Location: Deale, MD
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Re: Simple in-line hose filter without carbon?
^^ Actually, it 's hysterical, because the filter doesn't do spit. I just did some testing. The problem is contact time; go to any carbon manufacture web site, look at design data and contact times for the removal of anything, and the removal generally does not become significant until some minutes have passed. unlike air filtration, it takes time for the contaminants to diffuse over to the carbon and into the pores. The process is FAR from instantaneous. As I always suspected, hose-end filters are simply inefficient depth filters, removing some portion of organics and chlorine, but not much. They will, however, stop pipe scale, some of the gook that grows in the hose, and some sulfide. Did you know, for example, that to receive NSF certification, a device need only remove 25 % of the chlorine, and none of these are certified.
I just happened to have 2 brand new filters on my desk preparing for flow testing:
Chlorine in 1.2 ppm
Chlorine out 1.1ppm
Chlorine in 1.3 ppm
Chlorine out 1.2 ppm
Given testing error, they are the same. Given they are filled with basically the same amount of the same material, they are expected to be the same.
So my tank has been receiving a chlorine residual, which helps explain why it has stayed pristine with only annual cleaning and drying. I've used a variety of hose-end filters over the last 6 years, without thinking too much about it. I think I just assumed they would adsorb little and that they would filter some, which was all I asked of them. I knew chlorine was blowing through, I just hadn't bother ed to test how much. wasn't very interested.
One less mystery, no reason to look for another filter type, since the Camco filters are only $10 complete (Walmart).
And now you know the rest of the story.
BTW, carbon filters in RO units and may other applications are very effective (my home RO reads zero chlorine before the membrane--I got nosy) because the flow rate is very low, perhaps 1000 times slower. The contact time is sufficient. I have one process (glycol polishing) where the optimum contact time is over 24 hours (glycol is more viscous and the contaminants high in MW). No, we don't use the RO for drinking--I trust tap water and we need the minerals--it was free and we use it for humidifiers and CPAP.
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")
"Well, I just climb up to them."
by Joe Brown, English rock climber
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Last edited by pdqaltair; 06-06-2014 at 06:25 PM.