Plumbing guide
Under Sink Storage with a Water Filter or RO System
An under-sink RO system claims one full side plus the back: a typical filter bank runs about 15.5 x 5.25 x 17 in and its tank about 11 in across by 15 in tall (APEC ROES-50 numbers). Keep the cartridge faces reachable with about 4 in of clearance below them, then organize only the lane that remains.
Filter systems are the one under-sink obstacle that gets serviced on a schedule: cartridges change every 6 to 12 months, and whoever changes them needs hand room and a drip zone. Storage that packs against the housings turns each filter change into a full unload, so the layout starts from the service access, not from the leftover space.
Real footprints from the manufacturers: an APEC ROES-50 assembly measures about 15.5 in long, 5.25 wide and 17 tall, with a 4-gallon tank around 11 in across and 15 tall; an iSpring RCC7 runs about 15 x 5.5 x 16 with a 10.75-in tank. Mount the bank on one wall, stand the tank in the back corner, and the storage question becomes a single clear lane of 8 to 12 inches.
Recommended layout
Give the filter side to the filter: one shallow bin in front of the tank at most. All daily storage goes to the opposite lane and the front strip.
Start here: Split the cabinet into left and right lanes of about 10.5 in each. Use organizers that stop short of the trap bend, plus a low bin in the front strip.
Use this page's approach if
cabinets with an installed RO system, inline filter bank or water softener cartridge; the depth number above already subtracts a rear tank.
Skip or adjust it if
your filter is a small faucet-mounted or pitcher type; the standard center-pipe layouts apply unchanged.
| Storage zone | Max width | Max depth | Max height | Best use |
|---|---|---|---|---|
| Left zone | 10.5 in | 18 in | 18 in | Narrow slide-outs, bin stacks, side baskets |
| Right zone | 10.5 in | 18 in | 18 in | Narrow slide-outs, bin stacks, side baskets |
| Front strip | 29.5 in | 8.6 in | 9 in | Low trays and one-motion daily bins |
| Back strip | 29.5 in | 15 in | 18 in | Only if every joint stays visible and reachable |
Size classes that match this layout
| Size class | Shop at or under | Fit | Where it goes | Notes |
|---|---|---|---|---|
| Slim side basketvery narrow, 5-6 in lanes | 5.5 in W × 14 in D × 10 in H | Exact fit | Left zone | Rescues the sliver of space beside offset plumbing. Small capacity: best for brushes and refill packs stored upright. |
| Stackable binnarrow, 5-7 in lanes | 6 in W × 14 in D × 7 in H | Exact fit | Left zone | Fits the tight lane every other class gives up on; rental-safe. Buy open-front: the lower bin must stay reachable without unstacking. |
| Stackable binstandard, 8-11 in lanes | 9 in W × 13 in D × 8 in H | Exact fit | Left zone | The zero-risk default for any plumbing layout. Stack two high at most; the top bin needs 1 in of lift-out room. |
| Cleaning caddycarry kit, handle included | 10 in W × 13 in D × 11 in H | Exact fit | Left zone | The grab-and-go zone: parks front-center of the widest lane. Height listed with handle: the handle must clear the bend on lift-out. |
| Low turntableflat, spins under the bend | 10 in W × 10 in D × 3.5 in H | Exact fit | Left zone | Puts small bottles a spin away in heights nothing else uses. Keep it off the trap ring: the spin needs a flat clear footprint. |
| Low open trayfront strip, under the bend | 15 in W × 12 in D × 4 in H | Exact fit | Front strip | Lives under the trap where nothing else fits; doubles as a leak spotter. Must lift straight out in one motion without threading around the trap. |
| U-shaped cutout shelffixed cutout, centered traps | 16 in W × 11 in D × 12 in H | Exact fit | Largest clear zone | Spans the trap when the cutout truly matches its position and width. Cutout must exceed the trap assembly's widest point by 1 in. |
| Slide-out drawernarrow, for 6.5-8 in lanes | 8 in W × 16 in D × 13 in H | Good fit | Left zone | Daily-access winner for a clear side lane beside the trap or disposal. different style than you picked, still workable. Rails need about 0.25 in of side play and a clear travel path front to back. |
What not to buy here
Anything in front of the cartridge faces, bins that pin the tank's tubing, and pull-outs on the filter side; their rails need exactly the depth the tank took.
Mistakes this page exists to prevent
- Measuring depth at the empty side and buying deep bins for the tank side too.
- Blocking the tank valve or the line to the faucet, then kinking it when a bin gets shoved back.
- Forgetting the drip zone: cartridge changes always release a cup of water; whatever stands below gets wet.
Common questions
How much space does an under-sink RO system take?
Plan on the filter bank (about 15-16 in long, 5-6 wide, 16-17 tall) plus a tank about 11 in in diameter and 15 in tall, per APEC and iSpring's own dimensions. In a 30-in cabinet that is roughly one side and the back corner.
How much clearance do the cartridges need?
About 4 in below the housings so they can unscrew, plus hand room in front. If a bin has to move for a filter change, it is in the wrong spot.
Can I still have a pull-out with an RO system?
Usually only on the opposite side, and only if that lane keeps a clear rail path. Measure the remaining lane at its narrowest; tanks bulge exactly where rails want to run.
Would a tankless RO free up storage?
Yes: tankless units mount their full footprint on one wall and skip the 11-in tank, which returns the back corner to storage. It is a plumbing purchase, not a storage one, but it changes the map.