CPW uses chlorine. CWS uses chloramine. That one-sentence distinction is the most important thing nobody in the Charleston water treatment market explains.
Why it matters
Chlorine (Cl2) is a simple molecule that off-gasses from water relatively quickly. A basic granular activated carbon (GAC) filter handles free chlorine well. Your Brita pitcher, your fridge filter, your showerhead filter, all designed around free chlorine.
Chloramine (NH2Cl) is a compound of chlorine and ammonia. It's more stable, which is why utilities like CWS, Mount Pleasant Waterworks, and Dorchester County Water Authority use it. That stability means it doesn't off-gas easily and it doesn't respond to basic carbon media the way chlorine does. Catalytic carbon or extended-contact GAC is required.
Which utility serves your home
If you're on Summerville CPW (Nexton, Cane Bay, Carnes Crossroads, Foxbank, Summers Corner): chlorine.
If you're on Charleston Water System (West Ashley, James Island, parts of North Charleston): chloramine.
If you're on Mount Pleasant Waterworks: chloramine.
If you're on Dorchester County Water Authority (Knightsville area): chloramine.
Why this changes the equipment conversation
The filtration media that works for your neighbor in Summerville may not work for your friend in Mount Pleasant. When I test your water, I'll identify which disinfectant you're dealing with and what media actually addresses it.
Free test. Call (843) 302-5720.