ULP21-4021 Ultra-Low-Pressure RO Membrane – 4″ × 21″, 950 GPD

The ULP21-4021 Reverse Osmosis Membrane is a compact, ultra-low-pressure membrane element designed for efficient dissolved solids reduction in commercial and light-industrial water treatment systems. Its nominal 4-inch × 21-inch configuration supports installation in compatible 4021 pressure vessels and compact RO equipment.

Under specified test conditions, the ULP21-4021 provides a nominal permeate flow of 950 gallons per day (approximately 3.6 cubic meters per day) with a stable salt-rejection rate of 99%. Its ultra-low-pressure design helps deliver effective permeate production at lower pressure than many conventional low-pressure membrane elements.

The spiral-wound membrane element provides approximately 36 square feet of active membrane area. Its shortened 21-inch length allows substantial membrane capacity to be integrated into compact commercial systems where a full-length 4040 element may not be suitable.

The membrane is intended for appropriately pretreated, low-salinity feedwater such as qualifying municipal water, groundwater, and surface water. Proper pretreatment is essential for controlling sediment, hardness, scaling, iron, organic fouling, and oxidizing chemicals that could reduce membrane performance or shorten its operating life.

Technical Specification

Testing Conditions

Testing Pressure: 150 psi (1.03MPa)

Testing Solution Temperature: 25 ℃

Concentration of Testing Solution (NaCl): 1500ppm

pH value of Testing Solution: 7.5

Recovery Rate of Single Element: 8%

Operation Limits & Conditions

Max. Working Pressure: 600psi（4.14MPa)

Max. Volume of Feed Water: 16gpm（3.6 m3/h）

Max. Temperature of Feed Water: 45℃

 Max. Feed water SDI15: 5

pH Range of Feed Water during Continuous Operation: 3～10

pH Range of Feed Water during Chemical Cleaning: 2～12

Residual Chlorine Concentration of Feed Water : ＜0.1ppm

Max. Pressure Drop of Single Membrane Element: 15psi（0.1MPa）

Max. Pressure Drop of Single Pressure Vessel with Six RO Membranes: 50psi（0.34MPa）

Applications

◎ Drinking water production, such as: packaged water, direct drinking water, food processing water, etc.

◎ Purified water production, such as: pharmaceutical water, medical water, electronics water, etc.

Shipping Information

Optimal Purity Solutions is committed to fast, reliable, and professional fulfillment for our authorized dealer network.

Fulfillment & Processing

• Order Processing: Most in-stock orders ship within 1–2 business days

• Custom/OEM Builds: Lead times vary by configuration; your sales representative will confirm timelines

Shipping Coverage

• Domestic: Nationwide shipping throughout the United States

• International: Available for qualified distributors (terms and transit times vary)

Carriers & Methods

• Shipments are sent via trusted national freight and parcel carriers

• LTL/FTL freight available for pallets and bulk orders

• Expedited shipping options available upon request

Packaging & Handling

• Products are professionally packaged to protect against damage in transit

• Palletized and freight shipments are secured and labeled to industry standards

Tracking & Support

• Tracking information is provided once your order ships

• Our logistics team is available to assist with routing, delivery coordination, and special requirements

Important Notes

• Shipping costs are calculated based on weight, dimensions, destination, and service level

• Damages or discrepancies must be reported within 48 hours of delivery

• Products are sold exclusively through authorized water treatment dealers and partners