Under-Sink Reverse Osmosis Systems in Surprise

When the supply behind your tap blends and shifts, RO gives the kitchen faucet water that tastes the same every day.

An under-sink reverse osmosis system forces water through a membrane that removes most dissolved minerals and salts. In Surprise, city water averaged about 308–318 ppm total dissolved solids in its two largest systems in 2025, and EPCOR's Agua Fria district ranged from 182 to 692 ppm. RO brings drinking water well below either.

Dissolved solids by supplier

Mountain Vista city water averaged 307.5 ppm TDS and Desert Oasis 318 ppm in 2025 (City of Surprise). EPCOR's Agua Fria district reported a much wider 182 to 692 ppm (EPCOR 2025). Those minerals are what you taste in plain water, what clouds ice cubes, and what leaves film in a kettle. RO removes most of them at one faucet.

How the system is put together

Sediment and carbon pre-filters protect the membrane.
The membrane separates clean water from a concentrate that goes to the drain.
A small pressurized tank stores filtered water under the sink.
A polishing filter and a separate faucet deliver it; a line to the fridge is optional.

Pairing RO with a softener

If you soften the whole house, put RO after the softener. Softened water is gentler on the membrane, and RO removes most of the sodium the softener adds, so drinking water ends up lowest in minerals. On moderately hard city water, some households skip the softener and use RO alone for drinking and cooking.

What to compare

Look for testing to NSF/ANSI Standard 58, the waste-water ratio, tank size, and whether your sink has room and a spare faucet hole. RO is priced during the in-home visit; the cost of water softeners in Surprise covers the whole-house systems it often joins.

Questions homeowners ask

How much water does RO waste?

It varies by model. Older designs send several gallons to the drain per gallon filtered; newer ones are far more efficient. Compare the stated ratio before you buy.

Does RO take out the sodium a softener adds?

Yes, most of it. The membrane rejects the large majority of dissolved salts, including the sodium that ion-exchange softening puts in, which is why RO is the usual partner for a salt-based softener at the kitchen sink.

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