RO System Types in Florida: What You're Actually Paying For
Reverse osmosis comes in very different scales, and the price gap is mostly about how much water you are treating and to what quality.
Under-Sink RO (Point-of-Use)
A compact 4-5 stage unit under the kitchen sink that feeds a dedicated drinking-water faucet and (optionally) the refrigerator/ice maker. This is the most common FL choice for great-tasting drinking water without treating the whole house. Includes sediment and carbon prefilters, the RO membrane, a storage tank, and a post filter.
Premium / Remineralizing Under-Sink
Same footprint but adds a remineralization or alkaline stage (RO water is very pure and can taste flat; remineralizing restores minerals and raises pH) and often better fittings and a higher-output membrane.
Tankless / High-Flow RO
Newer designs skip the bulky tank, deliver water on demand at a higher flow, and often show a TDS readout. They cost more but free up cabinet space — popular in updated FL kitchens.
Whole-Home RO (Point-of-Entry)
A large system that treats all water entering the home. This is a significant investment with a big membrane array, storage, a re-pressurization pump, and often a drain to handle the reject water. Used mainly where the entire supply is very high in TDS or on problem wells — most FL homes solve drinking-water quality with a point-of-use unit instead.
FL Water Chemistry: Why RO Is Popular Here
Florida's water gives RO a lot to remove, which is exactly why these systems are common across the state.
Hardness & TDS
Groundwater from the Floridan Aquifer is often very hard and high in total dissolved solids. A softener swaps hardness minerals for sodium but does not lower TDS; RO actually removes the dissolved solids, which is why many FL homes run a softener for the whole house and an RO at the kitchen for drinking water.
Chloramine & Chlorine
Many South FL utilities disinfect with chloramine rather than chlorine. Chloramine is harder on RO membranes than chlorine, so a quality carbon prefilter (and on some systems a catalytic carbon stage) protects the membrane — worth confirming with your utility.
Coastal & Well Specifics
Coastal areas can see saltwater intrusion raising chlorides; the FL Keys largely run on RO-desalinated supply. Private wells may carry iron, sulfur (rotten-egg smell), sediment, or nitrates — all of which can foul an RO membrane and usually call for pretreatment before the RO.
FL Code: Drain Connection, Air Gap & Cross-Connection
RO is mostly a filtration appliance, but its connections fall under the plumbing code.
Reject Water to Drain
RO produces clean permeate and a concentrated reject (brine) stream that goes to drain. That connection must be made so wastewater cannot back-siphon into the system — commonly via an air-gap faucet or an approved air gap at the drain saddle. The Florida Building Code (Plumbing) treats this as an indirect waste / cross-connection concern.
Cold-Water Feed
RO connects to the cold supply (hot water damages membranes and filters). A dedicated feed valve taps the cold line under the sink.
Drain Saddle vs. Air-Gap Faucet
A drain saddle clamps onto the sink drain tailpiece above the trap for the reject line; an air-gap faucet builds the required air gap into the faucet itself. Some inspectors prefer the air-gap faucet on permitted work. Whole-home RO has larger drain and electrical needs and is more likely to involve a permit. Verify the adopted FBC edition and any local amendments with your AHJ.
Sizing, Efficiency & the Reject-Water Question
RO trades some water and some flow for purity, and FL homeowners care about both.
Output & Tank
Under-sink membranes are rated in gallons per day; a tank stores treated water so you get a normal flow at the faucet. Tankless units deliver on demand at higher flow but draw more instantaneously.
Reject (Brine) Ratio
Traditional RO sends several parts to drain for each part of permeate. Newer high-efficiency membranes and permeate pumps sharply improve that ratio — a permeate pump uses the drain-water energy to push the membrane, cutting waste and boosting output, which matters where pressure is low. In FL where water bills and conservation both count, efficiency is a real consideration.
Pressure
RO needs adequate incoming pressure to work well. Low-pressure FL homes (long runs, well systems, upper floors) benefit from a permeate or booster pump.
Maintenance: Filters, Membranes & FL-Specific Wear
RO is low-effort but not no-effort, and Florida water accelerates some of the wear.
Prefilters
Sediment and carbon prefilters typically get changed every 6-12 months; in sandy or high-sediment FL well water, sediment prefilters clog faster and may need more frequent changes. The carbon prefilter is what protects the membrane from chlorine/chloramine, so do not skip it.
Membrane
An RO membrane commonly lasts 2-5 years depending on water quality and prefilter upkeep. High TDS, chloramine without adequate carbon, and skipped prefilter changes all shorten membrane life.
Post Filter & Sanitizing
The final polishing filter is changed annually, and the system and tank should be sanitized periodically. A TDS meter (built in on many units, or a cheap handheld) tells you when the membrane is wearing out — rising product-water TDS is the signal.
Costs & What Drives Them in Florida
These are planning estimates for the system plus professional installation in the FL market. Ongoing filter and membrane replacement is a recurring cost not included in the install figure.
The System
A standard under-sink RO is the entry point; remineralizing and tankless units cost more; a whole-home RO is in a different category entirely because of the membrane array, storage, re-pressurization pump, and drain handling.
Installation
Mounting an under-sink unit where a cold feed, drain saddle, and faucet hole already exist is the floor of the range. Adding a drain saddle or air-gap faucet, running a new feed, drilling a granite/quartz counter for the faucet, or tying in the fridge all add labor.
Add-Ons & Source
Remineralization, permeate pump, or UV stages add to the system; well water often needs sediment/iron pretreatment or a softener upstream, which is a separate but related cost. Use the calculator tab to combine these.
DIY vs. Licensed: When to Call a Pro in Florida
A standard under-sink RO kit into an existing, ready spot is a reasonable DIY for a handy homeowner who is careful with the drain saddle and feed connections and leak-tests thoroughly. The risk is a slow under-cabinet leak — common, and on FL slabs it can reach flooring before you notice.
Call a Licensed Pro When
You need a new cold feed run, an air-gap faucet on permitted work, a faucet hole drilled in granite/quartz, a whole-home RO with its drain and re-pressurization pump, or well-water pretreatment design. New supply and drain connections are regulated plumbing work in FL; whole-home systems and well pretreatment especially benefit from a licensed plumber (CFC/CPC).
Insurance Angle
Under-sink water-treatment leaks are a known source of FL homeowner water-damage claims. A documented professional install — with photos of the feed, drain, and air gap — supports a claim if one is ever questioned.
Troubleshooting an FL RO System
Slow Flow / Little Water at the Faucet
(1) Low storage-tank air pressure (re-pressurize the tank bladder); (2) clogged prefilters; (3) low incoming pressure (consider a permeate/booster pump); (4) aging membrane. Check the tank pressure first.
Water Tastes Flat or Slightly Acidic
Normal for very pure RO water. A remineralization/alkaline stage restores taste and raises pH — common upgrade in FL.
Constant Drain Running / Won't Shut Off
(1) Tank not filling due to low pressure; (2) failed shut-off valve; (3) check valve issue. The system keeps sending water to drain if it never reaches shut-off pressure.
Rising TDS / Poor Removal
(1) Membrane near end of life; (2) chloramine damage from a skipped/exhausted carbon prefilter; (3) prefilters overdue. A TDS meter confirms it — replace the membrane and stay on the prefilter schedule.
Membrane Fouls Quickly (Well Water)
Iron, sulfur, sediment, or hardness reaching the membrane. Add sediment/iron pretreatment or a softener upstream of the RO; do not run problem well water straight into an RO membrane.
FL Permit Requirements
Usually No Permit in FL
- Installing a standard under-sink RO using an existing cold feed, drain saddle, and faucet hole
- Replacing filters, the membrane, or a like-for-like under-sink RO unit
- Adding a remineralization or post filter cartridge to an existing under-sink system
Permit Required in FL
- New cold-water supply piping or a new drain branch for the system (plumbing permit)
- Whole-home (point-of-entry) RO with its drain handling and re-pressurization pump
- A new dedicated circuit / outlet for a booster or re-pressurization pump (electrical permit)
- Well-water pretreatment / softener plumbing tied into the home's supply as part of permitted work
FL County Permit Fee Reference
For work that requires a plumbing or electrical permit (many simple jobs do not). Fees and timelines are approximate — verify with your local building department / AHJ before starting work.
| County | Permit Fee | Est. Processing |
|---|---|---|
Who Can Pull a Permit in FL?
A standard under-sink RO using existing connections is generally a no-permit appliance install in FL. New supply or drain piping, a whole-home system, or a pump circuit is regulated: per FL Statute 489.105, new plumbing supply/drain work is performed under a licensed plumbing contractor (CFC/CPC) and new electrical circuits under a licensed electrical contractor (EC). The reject-water connection must be protected against cross-connection (air gap / air-gap faucet). The homeowner exception applies only to owner-occupied single-family dwellings where the owner personally performs the work.
Verify any contractor's license at myfloridalicense.com and ask for proof of insurance before work begins.