A 1″ male-to-male NPT polypropylene union nipple with double O-ring sealing — the standard connector used between Big Blue whole-house filter housings and inline components. Automatic quantity discounts start at 2.

What it does

This union nipple connects two Big Blue whole-house filter housings (or a housing to an inline component) that both take a 1″ NPT female port. The double O-ring seal creates two sealing surfaces on the mating face — extra leak protection at the higher flow rates and pressures typical of a Big Blue installation.

A standard, everyday plumbing part in multi-stage Big Blue systems: you’ll typically use one nipple per housing-to-housing joint (so a 2-stage Big Blue uses 1, a 3-stage uses 2, etc.). Buy an extra to keep in the parts drawer for future service.

Key benefits

• ✓Male × male 1″ NPT — the standard size for Big Blue whole-house housings
• ✓Double O-ring seal — two sealing surfaces, better leak protection than a single ring
• ✓High-strength polypropylene — won’t rust like brass or seize like steel
• ✓Rated to 120 PSI — well above typical residential water pressure (40–80 PSI)
• ✓Fits Big Blue 10″×4.5″ and 20″×4.5″ housings, plus most 1″ NPT filter components
• ✓Automatic quantity discounts starting at 2 units

Specifications

Compatibility

Often used with

Good to know before you buy

• Check O-ring placement before installation — both rings must be seated in their grooves. Missing or displaced O-rings are the most common cause of a leaky Big Blue joint.
• Thread tape is not required when the O-rings are present. Adding tape can actually interfere with the O-rings seating properly.
• Hand-tighten evenly, plus a quarter turn if needed to seat the O-rings. Do not use a wrench — over-torquing cracks the plastic and defeats the seal.
• You typically need one nipple per housing-to-housing joint: 1 nipple for a 2-stage Big Blue, 2 nipples for a 3-stage. Order an extra to keep on hand.
• Cold water only — residential filtration systems. Not for hot-water lines.