How big is a reverse-osmosis system?#
An under-sink reverse-osmosis system is a compact filter-and-tank set, 9 to 18 inches wide and 14 to 18 inches tall, while a whole-home unit is far larger. The table below sorts the under-sink, tankless, and whole-home versions.
Reverse-osmosis system dimensions by configuration#
| Configuration | Width (in) | Height (in) | Depth (in) | Best for |
|---|---|---|---|---|
| Under-sink reverse-osmosis system | 14–18 | 14–18 | 5–9 | filtered drinking water at one faucet |
| Tankless reverse-osmosis system | 9–12 | 16–18 | 5–7 | a slim under-sink cabinet with no tank |
| Whole-home reverse-osmosis system | 20–30 | 40–60 | 12–20 | a garage or basement point-of-entry install |
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Installation clearances for a reverse-osmosis system#
- Under-sink footprint: 14–18 in in of cabinet width an under-sink reverse-osmosis system and its tank occupy.
- Tank height: 12–15 in in tall the storage tank of a reverse-osmosis system stands beside the filters.
- Drain saddle: A reverse-osmosis system sends its reject water to the drain through a saddle clamp on the sink tailpiece.
- Faucet hole: A reverse-osmosis system needs a dedicated faucet in the sink deck or an extra pre-drilled hole.
Will your reverse-osmosis system fit? Clearances and door swing#
For the common under-sink unit, the fit question is how much cabinet the filters and tank claim. Plan on 14 to 18 inches of cabinet width for the filter bank plus its 12 to 15 inch storage tank, which stands beside the cartridges and holds the treated water. A tankless model skips that reservoir, shrinking the footprint to as little as 9 inches wide for a crowded cabinet. Two connections leave the unit: a drain saddle clamps onto the sink tailpiece to send reject water away, and a dedicated faucet mounts in the sink deck or an extra pre-drilled hole. A whole-home system is a different animal at 40 to 60 inches tall, mounted at the point of entry in a garage or basement rather than under a sink. Measure the cabinet or wall space before choosing.
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Reverse-osmosis system sizes by type: under-sink reverse-osmosis system, tankless reverse-osmosis system, whole-home reverse-osmosis system#
The three formats scale from one faucet to the whole house. The under-sink model, 14 to 18 inches wide and tall, filters drinking water at a single tap and stores it in a small pressurized tank. The tankless version, just 9 to 12 inches wide and 16 to 18 tall, drops the storage tank and makes water on demand, ideal for a cabinet already crowded with plumbing. The whole-home system is the point-of-entry giant, 20 to 30 inches wide and 40 to 60 tall, mounted in a garage or basement to treat water for the entire house. Match the format to whether you want filtered water at one tap or everywhere.
Reverse-osmosis system dimensions: common questions#
How big is an under-sink reverse-osmosis system?#
The under-sink unit is 14 to 18 inches wide and tall, including the filter bank and the storage tank. It fits inside a standard sink cabinet alongside the trap.
Will a reverse-osmosis system fit under my sink?#
An under-sink or tankless model is designed to. The tankless version, as narrow as 9 inches, is the pick when the cabinet is already crowded with a disposer and plumbing.
How tall is the reverse-osmosis storage tank?#
The pressurized tank stands 12 to 15 inches tall and sits beside the filter housings. A tankless system has no tank at all.
What is a tankless reverse-osmosis system?#
A tankless system makes filtered water on demand instead of storing it, so it drops the reservoir and takes far less cabinet room — 9 to 12 inches wide versus 14 to 18 for a tank model.
How deep is an under-sink RO system?#
The under-sink filter bank is only 5 to 9 inches deep, so it mounts against a cabinet wall without blocking much. A tankless unit is even slimmer at 5 to 7 inches.
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