Dual-Stage Big Blue Whole House System — 10″ × 4.5″, 1″ Ports

This page covers specifications, installation, routine filter changes, and the exact replacement parts that fit this model.

Stage count and cartridge width are the two things that decide which filters fit. Getting either wrong means a set that won’t go in.

• Two Big Blue housings (this system) — takes a 2-cartridge set, 10″ × 4.5″.
• Three Big Blue housings — that’s the triple-stage system and needs a 3-cartridge set. Go to that page →
• Narrow housings (~2.5″) with 3/4″ ports — that’s a slim system and takes entirely different cartridges. Find your model →

Mounting, 1″ NPT connections, startup, and the filter-change procedure.

Open the manual →

• Cold main line, after the house shut-off, in a dry, level, freeze-protected spot out of direct sunlight.
• Check the IN/OUT markings on the caps — flow runs Stage 1 (sediment) then Stage 2 (carbon).
• Use 5–10 wraps of PTFE tape. Do not over-wrap or over-torque — that’s what cracks caps.
• Mount to a wood stud with the supplied screws; masonry or drywall needs anchors.
• For reversed flow, unbolt and flip the bracket — don’t invert the system.

This system doesn’t include built-in shutoffs. A valve on the inlet and the outlet turns future filter changes into a five-minute job instead of shutting off water to the whole house. A bypass loop is better still. If your installer didn’t fit them, close your main house shutoff before every change.

Component	Typical interval	Change sooner if…
Stage 1 — Sediment SED5-10BB	6–12 months 3–6 on heavy sediment or well water	House-wide pressure loss — that’s the classic clogged-sediment signal
Stage 2 — Carbon block CTO-10BB	6–12 months	Chlorine taste or smell returns
Housing O-rings	Inspect every change Replace every 12–24 months	Cracked, flattened, brittle, or weeping at the seam
Filter housings	3–4 years	Any crazing, hairline cracks, cloudiness, or a leak that a new O-ring doesn’t stop

Filter housings are under constant line pressure. Over years the plastic fatigues and can crack without warning — and a failed Big Blue housing on a 1″ main line releases water fast enough to flood a home.

Replace both housings every 3–4 years regardless of appearance, and immediately at any sign of crazing, cracking, or a persistent leak. Write your install date on each housing with a marker, or on the magnet, so the next change is easy to date.

The like-for-like replacement — the same two cartridges your system shipped with. One complete change: SED5-10BB + CTO-10BB.

Same fit, same two stages, with a coconut-shell carbon block in Stage 2 instead of the standard CTO block — denser media, longer carbon life, finer taste and odor polishing.

Cartridges are also sold individually — useful when heavy sediment means Stage 1 needs changing more often than Stage 2.

SED5-10BB — Sediment, 5 µm →  ·
CTO-10BB — Carbon block, 10 µm →

Whatever you swap, Stage 1 stays a sediment cartridge — it protects the stage behind it. Specialty media go in Stage 2, in place of the carbon block. With only two housings you have one specialty slot, so pick the media that matches your biggest water problem.

Cartridge	Best for	What it does
Stage 1 — Sediment
Pleated Sediment — Washable SED5-PLT-10BB · 5 µm	Heavy sediment & well water	Traps dirt, silt, sand, and rust like the standard sediment filter, but can be rinsed and reused instead of replaced. The right swap if Stage 1 is loading up at 3–6 months while Stage 2 still has life left.
Stage 2 — carbon options
Advanced Catalytic Carbon CAT-10BB · 25 µm · Centaur®	Chloraminated city water	Catalytic carbon made with Centaur® by Calgon. Standard carbon block has limited effect on chloramine — this is the correct swap if your utility disinfects with chloramine rather than free chlorine. Also helps reduce hydrogen sulfide (rotten-egg smell).
Premium Catalytic + KDF-85 CATKDF85-10BB · 25 µm	Chloramine + H₂S + metals · longest life	Catalytic carbon blended with KDF-85. Covers what the catalytic cartridge does and adds heavy-metal reduction. The KDF component also inhibits bacterial growth in the media bed, so it typically runs the longest of the carbon options.
Stage 2 — targeted water problems
Bone Char BC-10BB · 25 µm	Fluoride, heavy metals & arsenic	Bone char is one of the few media that helps reduce fluoride under suitable conditions, alongside heavy metals and arsenic. It also handles chlorine, taste, and odor, so it can stand in for the carbon stage rather than needing one of its own. Performance depends on contact time and water chemistry.
Iron Reduction + Softening Resin IRON-10BB	Clear-water iron & light softening	Softening resin that reduces dissolved iron, manganese, and some hardness — the usual fix for orange staining in sinks and laundry on well water. For clear-water (dissolved) iron only. If your water comes out of the tap already orange or rusty, the iron has oxidized and needs a backwashing iron system instead. A supporting stage, not a whole-house iron filter.
Scale Inhibitor — Salt-Free SCALE-10BB	Limescale protection	Conditions hardness minerals so they’re less able to form scale in pipes, water heaters, and appliances. No salt, no drain, no backwashing. Important: this does not remove hardness minerals and is not a water softener. Your water will still test hard and still feel hard — the benefit is scale protection for your plumbing, not soft water.

The right swap depends on what’s actually in your water, and more than one of these can be the wrong answer for a given problem. A water test is the reliable way to choose — guessing usually costs more than testing.

Browse all Big Blue specialty cartridges →  ·
Send us your water report →  ·
Free basic testing in San Diego →

Part	Part number	Notes
Big Blue Housing	HOUSING10BB	1″ ports, brass inserts, pressure-release cap
Housing O-Ring	—	The seal between housing and cap — the usual cause of a leak
Housing Wrench	WR-10BB	Replacement for the one in the box · Big Blue size only
Dual-Stage Mounting Bracket	BR-2-10BB	Steel, reversible for either flow direction
1″ Connection Nipple	FT-UN-1W-R	With O-ring · two per system

What you’re seeing	Most likely cause
Water pressure has dropped through the house	A loaded sediment cartridge in Stage 1. This is the normal end-of-life signal — change it. On heavy-sediment water this can happen at 3–6 months.
Leak where the housing meets the cap	O-ring not seated in its groove, or worn. Depressurize, reseat or replace the O-ring, lightly grease it.
Leak at a 1″ port connection	Too little PTFE tape, or the nipple O-ring is missing or pinched. Redo with 5–10 wraps. Do not over-torque — that cracks caps even with brass inserts.
Water weeping from the pressure-release button	Debris under the button seal, or a worn button. Depressurize and press it several times to clear it. If it keeps weeping, replace the housing.
Housing won’t unscrew	Pressure still in the housing, or it was overtightened last time. Confirm the water is off and you’ve pressed the release button, then use the Big Blue wrench.
Grey or cloudy water after a filter change	Carbon fines and trapped air. Normal. Flush a cold tap for 10–15 minutes; it clears within a few days.
Chlorine taste or smell has come back	Stage 2 is exhausted. Change it. If your utility uses chloramine rather than chlorine, standard carbon has limited effect — swap Stage 2 for a catalytic cartridge.
The cartridges I bought don’t fit	Almost always slim 10″×2.5″ cartridges bought by mistake. This system takes the wider 10″×4.5″ Big Blue size.
Water is still hard, or leaves scale	Expected. This is a filtration system, not a softener — it does not remove hardness minerals. A scale inhibitor cartridge protects plumbing but won’t soften the water.

Scope note: This is a sediment-and-carbon filtration system for improving everyday water — it is not a certified microbiological purifier and does not soften water or remove dissolved minerals. Do not use it to make microbiologically unsafe water safe to drink; on an untested well or under a boil-water advisory, treat your water accordingly first.

Please note: Filter life and reduction performance depend on your water chemistry, pressure, and usage, so results vary from home to home. This product is not certified to treat water of unknown quality and is not a substitute for testing your water. Descriptions use general, qualified language and are not health claims. When in doubt, test your water or ask us and we’ll help you build the right stack.