Reverse Osmosis in Central Texas: What It Removes, What It Doesn't, Costs and Wastewater

How an under-sink RO system works

A typical point-of-use RO system sits under the kitchen sink and feeds its own faucet (or a refrigerator line). Water passes through several stages:

1. Sediment pre-filter to catch particles.
2. Carbon pre-filter to reduce chlorine or chloramine. This matters because disinfectants can damage many RO membranes, and in the Austin area that means chloramine.
3. The RO membrane, a very fine semi-permeable membrane. Water is pushed through it under pressure, and most dissolved substances are rejected and flushed to the drain.
4. Storage tank (on traditional models) and a carbon post-filter to polish taste before the faucet.

Some newer "tankless" units use a pump instead of a storage tank.

What RO can reduce

EPA's WaterSense program, which sets efficiency criteria for point-of-use RO systems, says they can reduce contaminants including total dissolved solids, PFAS, arsenic, bacteria and viruses. In everyday terms for a Central Texas home, RO is very good at:

• Dissolved minerals (TDS). Our local water carries plenty. For example, Cedar Park reports total dissolved solids of 286 ppm and Leander reported 305 ppm. RO typically lowers TDS dramatically, which is a big part of why RO water tastes "cleaner" to many people.
• Disinfectant taste and odor, through the carbon stages.
• A long list of specific contaminants, depending on how the particular system is certified.

That last point matters. Performance claims belong to a specific, certified model, not to "RO" in general. Look for certification from an independent, accredited body, and read the performance data sheet that should come with the unit. It lists exactly what that model was tested to reduce.

What RO doesn't do

• It doesn't soften your whole house. An under-sink RO system only treats water at one faucet. Your showers, water heater, dishwasher and washing machine still get hard water. Scale protection comes from a softener (see our hard-water guide).
• It isn't a fix for unsafe water. If you're on a well or have a specific contamination concern, start with a lab test and follow guidance for that contaminant. Choose equipment certified for it.
• It doesn't last forever without maintenance. Pre-filters, post-filters and membranes all need periodic replacement. A neglected system can perform worse than tap water.
• It isn't "pure" water. RO greatly reduces dissolved substances, but it doesn't remove 100% of everything.

A note on health claims: utilities point out, in the federally required wording of their annual reports, that water meeting federal standards may not offer additional health benefits when filtered through a point-of-use device. Most people choose RO for taste, convenience (no more hauling bottled water) and peace of mind about specific contaminants. We won't promise health outcomes.

Wastewater: the part people don't mention

RO sends some water down the drain to carry away what the membrane rejects. EPA's WaterSense program says a typical point-of-use RO system can produce up to 10 gallons of reject water for every gallon of treated water. Systems that earn the WaterSense label must send 2.3 gallons or less to the drain per gallon produced.

In a region that regularly faces drought restrictions, that difference matters. If you're buying an RO system, ask whether it's WaterSense-labeled or what its rated efficiency is. Some systems also use a permeate pump or other design features to improve efficiency.

Why pair RO with a softener?

In hard-water areas, the RO membrane is constantly rejecting calcium and magnesium. Many manufacturers recommend softened or lower-hardness feed water to help the membrane last. Most of the northwest corridor reports roughly 11 to 15 gpg. In those homes, an RO system downstream of a softener is the common setup. Check the manufacturer's feed-water specifications for the model you choose.

There's also a taste reason. Softened water contains a bit more sodium. RO at the drinking tap reduces that, giving you soft water for the house and low-mineral water for drinking.

What does RO cost?

Costs vary a lot by brand, features and installation, so treat any single number with caution. Here's what to plan for:

• Equipment. Retail under-sink RO units range from budget systems to premium tankless models.
• Installation. This includes a dedicated faucet (often drilling the countertop or using an existing sink hole), a drain connection with the proper air gap or drain fitting, a cold-water connection, and space for the tank under the sink. A refrigerator or ice-maker line adds work.
• Ongoing filters. Pre-filters and post-filters are commonly replaced on a schedule of months, and membranes less often. The schedule depends on the model and your water.
• Water. Use the wastewater ratio above to estimate. A WaterSense-labeled unit wastes far less.

Our pricing: RO installation starts at $649 installed. That covers a professionally installed under-sink system with a dedicated faucet. Your exact quote depends on the system and your kitchen. We'll explain the filter schedule and costs upfront so there are no surprises.

Is RO right for your home?

RO is a great fit if:

• You buy bottled water or use a pitcher filter and want something better and more convenient.
• You dislike the taste of chloramine or "minerally" water.
• You want reduction of specific contaminants and choose a system certified for them.

It's not the right first purchase if your main complaint is scale on fixtures and appliances. That's a softener problem. And if you're on a private well, test first.

The bottom line

Under-sink RO is one of the best ways to get great-tasting drinking water from Central Texas taps. It's not whole-house treatment, it needs regular filter changes, and its wastewater varies a lot between models. Choose a certified, efficient system, pair it with a softener if your water is hard, and keep up with maintenance.