The inline US4-13 under-sink water filter delivers filtered water from your existing faucet.
Our company has been offering this model for over 20 years, and thousands of happy customers use it. It’s our most popular under-sink filter!
Never Runs Out
Product Overview:
- Designed to replace and retrofit discontinued NSA 100S and NSA 100SX systems using the same tubing size and fittings, and it includes a pressure-reducing valve.
- A strong choice for households that want better-tasting drinking and cooking water without installing a separate faucet.
- Rated for 1 to 2 GPM and up to 25,000 gallons, and it uses granular activated carbon plus KDF 55 media to reduce chlorine taste and odor, lead, sediment, and trace chemical contaminants.
- Uses bacteriostatic media that help inhibit bacterial growth within the unit.
Features of the US4-13 Under-Sink Water Filter
- Removes chlorine, bad taste, odor, and lead
- Removes dirt, rust, and sediment
- Bacteriostatic KDF media prevents bacterial growth within the unit
- Includes tubing, fittings, and instructions
- 3 years of maintenance-free performance
- Made in the U.S.A.
Compatibility First: Always Confirm Fit Before You Buy
Confirm your current NSA model and under-sink clearance, then replace your filter with the US4-13 to keep great-tasting drinking and cooking water flowing from your existing faucet.
Replaces
- NSA 100S
- NSA 100SX
Confirm fit notes
- Match your current system model name on the label or paperwork.
- This replacement is designed to use the same tubing size and fittings as the NSA models listed above.
- Confirm you have enough under-sink space for a unit that measures 14 inches tall by 5 inches in diameter.
- If you are installing for the first time, confirm your cold water line and under-sink layout allow for an inline filter and tubing runs.
If you are unsure, match the model name and port size first, then confirm the available under-sink clearance.
Who Should Buy the US4-13 Under-Sink Water Filter?
Choose the US4-13 if you want/need:
- Filtered water from your existing faucet
- An inline under-sink system that does not require a dedicated RO faucet
- A replacement for NSA 100S or NSA 100SX
- A long service life with low routine maintenance
- Improved water taste for drinking, coffee, tea, cooking, and ice
When to replace
Typical replacement timing
- Replace when you reach 25,000 gallons or about 3 years of typical use, whichever comes first.
- Common signs that it is time to replace
- Reduced flow at the faucet compared to normal
- Taste or odor changes that return over time
- Visible sediment concerns you did not notice before
- You cannot confirm the remaining service life based on usage
If your home has high usage or challenging water conditions, replace sooner.
How to Replace the US4-13 Under-Sink Water Filter: Step-by-Step List
- Turn off the cold water supply under the sink.
- Open the faucet to relieve pressure.
- Place a towel or small pan under the filter area to catch drips.
- Note the direction of flow on the existing unit or tubing layout.
- Disconnect the tubing from the old unit using the fitting release method for your connection type.
- Remove the old unit and position the new US4-13 in the same orientation.
- Connect the inlet and outlet tubing to the new unit and confirm the connections are fully seated.
- Turn the water back on slowly and check all fittings for leaks.
- Flush the system according to your included instructions until the water runs clear, and the initial carbon fines are gone.
- Recheck for leaks after a few minutes of flow and again later the same day.
Specifications
| Spec | Value |
| Model | H2O-US4-13 |
| Application | Inline under-sink filtration, filtered water from the existing faucet |
| Recommended flow | 1 to 2 GPM |
| Capacity | 25,000 gallons |
| Media type | Coconut shell activated carbon and KDF 55 |
| What it reduces | Chlorine taste and odor, lead, sediment, trace chemical contaminants |
| Bacteriostatic protection | KDF media helps inhibit bacterial growth within the unit |
| Port size | 3/8 inch ports |
| Dimensions | 14 inches high x 5 inches diameter |
| Weight | About 8 to 8.2 lbs. shipping weight |
| Included | Pressure reducing valve, tubing, fittings, instructions |
| Country of origin | Made in USA |
FAQs on the US4-13 Under-Sink Water Filter
Q: Does this replace the NSA 100S?
A: Yes. The US4-13 is designed to replace and retrofit the discontinued NSA 100S.
Q: Does this replace the NSA 100SX?
A: Yes. It is listed as an excellent replacement option for the discontinued NSA 100SX.
Q: Will this work with well water?
A: It can, but results depend on well water conditions. For heavy sediment, iron, or strong odors, additional prefiltration may be needed.
Q: Does it reduce chlorine taste and odor?
A: Yes. The activated carbon media is designed to reduce chlorine taste and odor.
Q: Does it reduce lead?
A: Yes. The system is listed for lead reduction using carbon and KDF media.
Q: Does it remove bacteria?
A: This system is designed to filter and reduce specific contaminants and uses bacteriostatic media to help inhibit bacterial growth within the unit. If you need to disinfect water for microorganisms, UV or other disinfection methods are typically used.
Q: Do I need a new faucet?
A: No. This system is designed to provide filtered water through your existing faucet.
Q: How do I know when it is time to replace it?
A: Replace when you reach the rated capacity or if you notice reduced flow or a return of taste and odor issues.
View a cutaway diagram of typical under sink filter to see how it filters your water.
