Quick Answer: The iSpring WGB32B is a solid, plain-vanilla city-water filter: a 5-micron sediment cartridge and two 5-micron coconut-shell carbon blocks in 20" x 4.5" housings, rated up to 15 GPM and 100,000 gallons (iSpring's estimate is about a year for a family of four). Buy it to cut chlorine and grit, or to protect a softener's resin. Don't buy it for hardness, TDS or well-water iron. If your city uses chloramine or you notice a faint sulfur smell, the WGB32B-KS with KDF is the better version.
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This is a hard-water site, and the WGB32B does nothing to hardness. So why review it? Because a lot of our readers end up buying one anyway, often in the same order as a softener, and they want to know if it's worth the wall space. Usually it is. But "WGB32B" covers half a dozen different cartridge setups, and buying the wrong suffix is the most common mistake.
I haven't installed one. The specs below come from iSpring's documentation as published by SupplyHouse and from the Amazon listings for each variant.
In this guide
- Three cartridges, one job
- Which WGB32B? Match the suffix to your water
- The 100,000-gallon rating, in calendar terms
- About the connectors in this listing
- The first hour after install
- Replacement cartridges: standard sizes, so you have options
- How it fits with a softener
- Who shouldn't buy the base WGB32B
- Other ways to go
Three cartridges, one job
The base WGB32B lines up like this:
- FP25B: 5-micron polypropylene sediment cartridge
- FC25B: 5-micron coconut-shell carbon block (CTO: chlorine, taste, odor)
- FC25B: a second identical carbon block
Two carbon blocks in series is the design choice that matters. The second one picks up what the first lets through as it loads up, so you get more contact time and more total media than a single-carbon system.
The rest of the published spec:
- Flow: up to 15 GPM
- Ports: 1" NPT, with 20" x 4.5" ("Big Blue" size) cartridges
- Rated capacity: 100,000 gallons, which iSpring calls a full year for a family of four
- Claims: up to 99% chlorine reduction, plus up to 95% of sediment, rust, pesticides, herbicides and industrial solvents. The claims cite SGS lab testing from 2018. iSpring says the carbon blocks were tested by an independent third party to "meet NSF/ANSI standards" but doesn't name which standards.
- Won't reduce: total dissolved solids. iSpring's own retailer copy states it plainly: this is not an RO system.
- Warranty: 1 year, with an extended warranty if you register online (term not stated), plus lifetime US tech support
- Intended for: municipal water. For wells, iSpring points you to the WGB32BM, its iron and manganese version.
Which WGB32B? Match the suffix to your water
| Variant | Middle stage | Buy it if… |
|---|---|---|
| WGB32B (this one) | Carbon block | City water with free chlorine, little else going on |
| WGB32B-KS | KDF + carbon | Chloramine, or a faint rotten-egg smell |
| WGB32B-DS | Polyphosphate | Scale on fixtures and you won't run a softener |
| WGB32B-PB | Lead-reduction block | Older service lines or a lead concern on your utility report |
| WGB32B-PFKS | PFAS / heavy metals media | Your utility reports PFAS |
| WGB32BM | Iron / manganese | Well water with light staining |
Check your utility's annual water quality report before choosing. If it says "chloramine" or "combined chlorine," don't buy the base model. Plain carbon blocks sized for free chlorine are slow against chloramine. We explain the resin side of that in how chloramine affects a water softener.
The 100,000-gallon rating, in calendar terms
The rating holds up for a typical four-person house at around 300 gallons a day. That's 109,500 gallons a year, right at the rating. But it's the sediment cartridge that usually decides when you change:
- Clean city water: you'll likely get close to a year on everything.
- Construction nearby, water main work, older pipes: the FP25B can clog in months, and you'll feel it as a pressure drop at the shower.
- Five or more people: plan on carbon changes at around 9–10 months.
A practical habit: replace all three cartridges at the same time the first year, note the date on the housing with a marker, and then adjust based on how the sediment cartridge looked when it came out.
About the connectors in this listing
This particular Amazon listing ships with 3/4" push-fit braided stainless steel hose connectors. They make the install a lot friendlier for a DIYer: no soldering, and the flexible hose takes up small misalignments. The housings themselves are 1" NPT. If your main is 1" and you care about every bit of flow (a big house, a well pump at the edge of its capacity), hard-pipe it at full 1" instead. For most 3/4" homes, the kit is fine. Our whole house filter install guide covers bypass loops and mounting height.
The first hour after install
Here's what install day looks like once the housings are on the wall:
- Leave the cartridges out and open the inlet slowly to check every joint for drips under pressure. Push-fit connections either seal or they don't, and you want to find out before the housings are full of water.
- Shut off, drop the housings, and load cartridges: the FP25B in housing one, then the two FC25B carbon blocks. Check that each O-ring sits flat in its groove. A pinched O-ring is the usual cause of a weeping housing.
- Open the inlet slowly again, purge trapped air (use the pressure-release button on the heads, or just open a tap and let it sputter), and let a cold tap run until the water clears. New carbon blocks shed a little fine dust at first.
- Then open the softener valve if you have one downstream. That way the carbon fines and air don't go through the resin bed.
Replacement cartridges: standard sizes, so you have options
The FP25B and FC25B are standard 20" x 4.5" Big Blue cartridges. That's one of the WGB32B's quiet advantages. iSpring sells its own full replacement sets (the F3WGB32B pack), and many other brands make cartridges in the same size. You can also change your mind on media later. Swap a carbon block for a KDF/carbon cartridge if your city switches to chloramine, without replacing the housings.
When you buy third-party cartridges, check the micron rating and whether it's a true carbon block or loose granular carbon. Granular carbon flows freely, but it gives less contact time at 15 GPM than the block iSpring specifies.
How it fits with a softener
Most homes should put the WGB32B before the softener. Here's why:
- Chlorine slowly degrades softener resin. The carbon removes it first, which helps the resin bed last longer. See how chlorine damages softener resin.
- Sediment stays out of the control valve, where grit wears seals and pistons.
- You get filtered water at every tap, including the ones that bypass the softener, as long as the filter sits before any bypass branch.
What the pair still won't do: remove nitrates, TDS, bacteria or arsenic. Our list of what a water softener does not remove applies to a carbon filter too, more or less. And if you're tasting chlorine after installing both, see chlorine taste after a water softener. The carbon is usually overdue.
Who shouldn't buy the base WGB32B
- Well owners with iron, manganese or sulfur. Look at the WGB32BM or KS, or a dedicated iron filter.
- Anyone hoping to soften water. It won't move your hardness reading at all.
- Chloramine cities. Get the KS.
- Tiny utility rooms. Three 20" housings take a wide stretch of wall plus drop clearance below.
Other ways to go
iSpring WGB32B-KS. Same frame and housings, with a KDF/carbon middle stage that the listing says reduces chlorine, chloramine and hydrogen sulfide. For a lot of US cities, it's the right WGB32B. Check price on Amazon
iSpring WGB32B-DS. Sediment, polyphosphate and carbon block. It's for people who want scale control on fixtures and heaters but won't add a softener. Polyphosphate inhibits scale. It doesn't soften. Check price on Amazon
Home Master HMF2SmgCC. A two-stage system using up-flow KDF85 and catalytic carbon, listed at 10 gpm. Catalytic carbon is the media usually chosen for chloramine. The lower flow rating suits smaller homes. Check price on Amazon
If your report says free chlorine and you want the straightforward version: Check price on Amazon