Reverse Osmosis Drinking Water Systems in Central New Jersey

What actually happens under the sink

A residential RO unit is a row of housings mounted inside the kitchen cabinet, fed from the cold line and finished with its own small faucet at the sink. Water moves through it in stages, and each stage protects the next one.

The membrane is the heart of it. Pressure from your plumbing drives water molecules through a sheet with pores far smaller than a bacterium, while most dissolved salts, metals, and many larger organic molecules stay behind and are rinsed to the drain. Everything before the membrane exists to keep it alive; everything after it is about taste.

• Sediment prefilter: catches rust flakes, sand, and grit so they do not clog later stages.
• Carbon prefilter: removes chlorine or chloramine, which would otherwise break down a thin-film membrane over time.
• RO membrane: does the heavy reduction of dissolved solids, and is the stage most certification claims rest on.
• Post filter: a small carbon polish that picks up any taste the storage tank or tubing adds.
• Optional remineralizing cartridge: adds back a little calcium and magnesium, covered further down.

Why people in this area ask about RO

Most requests start with a number in a utility report. Monroe Township's utility, which draws from nine wells in the Old Bridge and Farrington sand aquifers, reported a PFOA average of 7.68 ppt with a high of 12 in its report on 2024 results. That is inside New Jersey's 14 ppt limit, and the utility reported no violation. It is also above the 4.0 ppt federal limit EPA finalized in April 2024, which carries an April 2029 compliance date. Households who would rather not wait for that date often look at a drinking water unit first, since it treats the water people actually swallow. The Monroe page has the rest of that report, and our PFAS filtration page compares RO with carbon and resin options.

Other common reasons: a softened house where someone is watching sodium, a taste people simply do not like, or a private well result that came back high for something an RO membrane is good at reducing. Some households on NJ American Water's Raritan System notice its published sodium range of 32 to 99 ppm, which is listed against a recommended upper limit of 50 ppm, and want a lower-sodium glass. None of this means a local supply is unsafe. It means people want a specific number lower at one tap, and RO is a direct way to do that.

NSF/ANSI 58 and the fine print on a claim

The standard that covers home reverse osmosis units is NSF/ANSI 58. A model certified to it has been tested for structural integrity, materials safety, and total dissolved solids reduction. That is the baseline, and it does not by itself say anything about PFAS, lead, arsenic, or nitrate.

Each of those is a separate reduction claim that the certifier lists by name for that exact model. So the useful question is not "is it certified" but "certified for what." Pull up the listing on the certifier's own site, match the model number on the box, and read which contaminants appear. If PFOA and PFOS are not on that list, the unit has not been verified for them, whatever the packaging implies. The same goes for lead and arsenic, and for arsenic it matters which form is present, since the two forms behave differently on a membrane.

Claims also assume the tested feed pressure and filter change schedule; a unit run past its cartridge life will not perform like the test unit did.

Tank or tankless, and where the reject water goes

Classic RO units fill a small pressurized storage tank slowly and deliver from it when you open the faucet. Tankless designs use a booster pump to produce water on demand and fit in a tighter cabinet, but they need an electrical outlet under the sink. Neither is better in every kitchen; it comes down to space, whether there is power nearby, and how much water you draw at once to fill a pot.

Every RO system sends part of the incoming water to the drain to carry away what the membrane rejected. Ratios vary a lot by design, and newer units with permeate pumps or recirculation waste noticeably less than older ones. The drain connection itself needs an air gap so wastewater can never siphon back into the unit, which is one reason this is plumbing work and not a quick weekend swap.

Remineralization and the taste question

RO water is very low in minerals, and some people find it flat. A remineralizing post filter adds a modest amount of calcium and magnesium back so the water tastes closer to what they are used to. It is optional, it is another cartridge to change, and it does not undo the contaminant reduction the membrane already did.

Keeping an RO unit working

Most of the cost of owning RO is cartridges and the occasional membrane, so ask about them before choosing a model. As a rule of thumb, prefilters are changed on a schedule counted in months and membranes on one counted in years, and hard water, sediment, or iron shortens both. Follow the interval in the manual for the unit you buy rather than any general rule.

Signs a stage is due: the flow at the RO faucet slows, the tank takes far longer to refill, or a TDS meter reading creeps upward compared with when the system was new. Sanitizing the housings and tank at membrane change time is part of good service, and so is writing the date on each cartridge.

Is whole-house reverse osmosis ever the answer?

Rarely, for a typical home. Treating every gallon that goes to toilets, laundry, and the lawn with a membrane means large storage, repressurization pumps, and a lot of reject water, and the very low mineral content can be aggressive toward metal plumbing unless it is corrected afterward. It shows up mainly where a well result is high for something that point-of-use treatment cannot reasonably handle for the whole house. For most households, a whole-house carbon or filtration system for showers and laundry plus RO at the kitchen tap covers the need.

On a private well, sediment, iron, manganese, and hardness are usually dealt with upstream before RO, or they shorten membrane life. The well water treatment page walks through that order.

From the form to a working faucet

Tell us your ZIP and whether you are on a utility or a well. A local water treatment professional reaches out, reviews your utility's annual report or your most recent lab results, and looks at the sink cabinet, the drain, and whether there is an outlet. If testing would help settle the decision, they explain it first; see water testing for how certified labs fit in. The consultation is free, and recommending nothing is a valid result.

Connecting an RO unit to the supply and the drain counts as installing water treatment equipment, which New Jersey places within the scope of plumbing under N.J.A.C. 13:32. The person doing the work for you must be properly licensed for it.