Inline Under Sink Water Filter with 25,000-Gallon Capacity

$220.00 $199.00

Inline under sink water filtration system designed to replace NSA models 100S and 100SX. The iUS4-25K drastically improves your water's taste while eliminating its odor and color for 25,000 gallons. Its 5-stage filtration process includes bacteriostatic media (KDF + GAC) which prevents bacteria growth while eliminating chlorine and a variety of chemicals and organic contaminants.

Note: This model includes a cartridge, tubing and fittings for a brand new installation. If you simply need to replace the filter cartridge on your existing setup, the iUS4-25K-CART is all you need.

  • 25,000-gallon capacity
  • Replacement for NSA models 100S and 100SX
  • Bacteriostatic media prevents bacteria growth (algae, fungi)
  • 2 gpm flow enables filtration for multiple appliances
  • Available with quick-connect or compression fittings
  • Includes 50-psi pressure regulator
  • Includes 1-year pro-rata warranty

Compression Fittings (optional)

(this unit comes standard with quick connect fittings. Check the box to receive compression fittings on your unit.)

SKU: iUS4-25K Category:


The iUS4-25K under sink inline water filter processes 100% of the cold water that runs through a sink’s main faucet. Designed to replace the long-running NSA water filter 100S model, the iUS4-25K capably processes 25,000 gallons of water. It also works great on water coolers, appliances, boats, RVs or in any other inline arrangement.

The iUS4-25K features a 5-stage filtration process including KDF media and GAC (granular activated carbon), plus three 5-micron filter pads. The bacteriostatic media prevents bacteria growth and improves the taste of your water while eliminating its odor and color. A standard unit includes 3/8″ quick-connect fittings at the inlet and outlet. Compression fittings are also available for this unit. After flowing upward through the filter cartridge, the filtered water then continues to the main faucet of the sink, providing great-tasting, chlorine-free water.

NSA Water Filter 100S Model

The iUS4-25K is manufactured according to the design of the former 100S model by NSA (as well as the 100SX model). Various improvements to the design have been made over the years to ensure the quality and effectiveness of this inline unit. It includes a 50 psi pressure regulator which protects the filter cartridge and your plumbing hardware.

Maximum Capacity 25,000 gallons (94,635 liters)
Maximum Flow 2.0 gpm (7.57 lpm)
Unit Dimensions 16.5″ height x 5.0″ diameter (41.9 x 12.7 cm)
Box Dimensions 18″ x 7″ x 6″ (44.5 x 16.5 x 14.6 cm)
Unit Shipping Weight 10.4 lbs. (4.72 kg)



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