Which size fits your home

This is the size Aidan recommends for smaller homes: "Two to four people, a 1.5 cubic foot" in his carbon filter video. It fits a townhouse, condo or a one or two bathroom house where two showers rarely run at once.

How to pick: count the showers and appliances that run at the same time, not only the people. A shower is 2.5 GPM or less. If your utility uses chloramine, or you cannot tell, use the chloramine column. Between two sizes, the bigger one gives more margin and longer carbon life; the smaller one costs less up front and needs refills sooner.

Why our flow numbers look lower than other brands'

A flow rating on a carbon tank can mean two things. Peak flow is how much water can pass through the tank. Treatment flow is how fast water can move through and still spend enough time in the carbon to be treated. Calgon Carbon, which makes Centaur, sizes chloramine at 1 cubic foot of Centaur per 2.5 GPM, about 3 minutes of contact. Chlorine reacts faster, in about 2 minutes. So this tank, with 1.5 cubic feet of Centaur, fully treats chloramine up to 3.7 GPM and chlorine up to 5.6 GPM. A modern shower head is rated 2.5 GPM or less, and a home rarely holds its peak for long. Above the treatment flow the water keeps flowing; for those minutes a little more chloramine gets through.

Most whole house filters publish only a peak number (9 to 25 GPM) and no carbon volume, so you cannot work out how long the water spends in the carbon. We publish the carbon volume and the treatment flow for chloramine and for chlorine so you can check the math. Peak flow we have measured only on the 2.5 (about 17 GPM); every size uses the same 1 inch Clack head and bypass, with no gravel bed.

Chlorine or chloramine?

Your water utility's annual Consumer Confidence Report says which disinfectant it uses. Chloramine needs more contact time than chlorine, so if your utility uses chloramine, size by the chloramine column; if it uses chlorine only, each size covers about half again as much flow. Not sure, or the report is confusing? Send it to Aidan by text at 443-277-2204 and he will tell you which size fits.

Sources: Calgon Carbon, Guidelines for the Removal of Chloramine (Centaur, 2020); Urbans Aqua EBCT guide (chlorine about 2 minutes). People and bathroom bands are ours, sized to the chloramine column.

On a private well? The same tank is set up for well water as the whole house carbon filter for well water; on a well it goes last, after the sediment filter, iron filter and softener.

What ships

• Vortech 10x54 mineral tank, black, with a Vortech plate at the bottom that spreads the water evenly, so no gravel layer is needed. It ships empty.
• Clack C1190 non-electric in/out head, set up for upflow service, with the bypass valve pre-installed. NSF/ANSI 44, 61 and 372 certified (Clack in/out head).
• 1.5 cubic feet of Centaur 12x40 catalytic carbon by Calgon Carbon, in one 1 cubic foot bag and one 1/2 cubic foot bag (1 x 1 cu ft bag, 1 x 1/2 cu ft bag). It is poured into the tank at install.
• Fill funnel for pouring the carbon in with the head off.
• Free shipping to the lower 48 states, by freight.

What does not ship

• Plumbing fittings are not included; the head has 1 inch male connections and your plumber supplies the fittings for your pipe (PEX, copper, CPVC or PVC).
• No drain line or electrical outlet is needed, so none is included.
• Install instructions: the manufacturers do not put any in the box. Use our whole house water filter install guide and Aidan's install videos, or text Aidan at 443-277-2204.

System

Centaur 12x40 (Calgon data sheet)

Reduces

Chlorine and chloramine, with the taste and smell they leave; disinfection byproducts (THMs and HAAs, which form when chlorine meets organic matter); VOCs (volatile organic chemicals such as solvents and fuel components), herbicides and pesticides; and general taste and odor. Activated carbon also reduces some PFAS. This tank is not certified for PFAS removal and we do not publish a removal percentage.

Does not remove

Carbon does not remove hardness (calcium and magnesium), so scale and spots need a water softener; if spots are your main complaint, text Aidan your hardness number and he will size the pair. It does not remove fluoride, lead, nitrate, sodium or dissolved solids (Aidan uses other filtration for lead and fluoride), and it does not disinfect. It does not need a drain, so it cannot backwash out heavy sediment: if your toilet tanks collect grit or you get brown water after main breaks, add a 20 inch Big Blue 5 micron sediment filter ahead of it.

Prices and claims below are from each company's own pages on Nov 3, 2026. They change; check before you buy.

Closest SpringWell size: SpringWell CF4 (10x54)

SpringWell CF4 lists at $1,523 ($1,294.13 on sale) and is rated 12 GPM; a bypass and connector add $78.74 bypass + $83.99 1 inch connector. This filter is $1,495 with the bypass valve included. Where SpringWell is ahead: a longer warranty, a longer money-back window, a sediment filter in the box and media that comes in the tank. What those mean after you buy: the 6-month window covers only unused, uninstalled systems; the sediment cartridge is replaced every 6 to 9 months; and the media life promised on their product page (10 years) is 6 years in their own warranty. Where we are ahead: a named carbon you can look up, honest flow math, and Aidan, who sizes the tank from your water report and supports your plumber by phone.

Sources: springwellwater.com whole house water filter page, warranty page and CF1/CF4 install manual; softprowatersystems.com whole house upflow catalytic carbon filter page; uswatersystems.com Bodyguard page and rebed kits.

Where it goes

On the cold water main line where it enters the house, after the main shutoff and before the water heater and any water softener. Chlorine shortens the life of softener resin, so on city water the carbon goes first and the softener after it. Keep it out of freezing temperatures and direct sun. If your outside spigots tee off before this point, irrigation water does not use up carbon.

The steps your plumber follows

1. Shut off the main and open a faucet to relieve pressure.
2. Stand the empty tank in place and tape over the top of the center tube, so no carbon falls into it. Carbon in the tube means no flow.
3. Pour the carbon in through the funnel, then add water just above the carbon so it starts soaking and pushing out its air.
4. Remove the tape and thread the Clack head onto the tank.
5. Connect the inlet and outlet with 1 inch fittings, following the flow arrows. The bypass labels are easy to misread; text Aidan a photo if you are unsure.
6. Leave the bypass in bypass and turn the house water back on; the house has normal, unfiltered water while the carbon soaks. Calgon recommends soaking Centaur for 12 hours, so the usual plan is that your plumber finishes here and you do the last step the next morning (about 15 minutes, no tools). If you need filtered water the same day, wait at least 10 minutes and expect more black fines the first few days.
7. If a softener or cartridge filter comes after this tank, put it in bypass for this first flush so carbon fines do not go into it. Open a cold tub faucet, turn this tank's bypass to service slowly, and when water runs, bring it up slowly to full pressure. Run it until it runs clear, usually 10 to 15 minutes, then put the softener back in service.

What to expect the first week

Black carbon fines on and off for two or three days are normal (Aidan, after refilling his own: "Saw black stuff on and off for like two or three days"). Run a tub or an outside spigot until it clears. Milky water that clears from the bottom of the glass up is fine air bubbles, not carbon. Opening the main all at once is the usual cause of carbon in the valve.

Step-by-step with photos: how to install a whole house water filter.

Between refills: nothing

No salt, no backwash, no settings and no annual service.

When to refill

Aidan's estimate for this size: about 4 to 5 years for two to four people. Carbon does not warn you when it is spent, and once it is exhausted it can release what it caught, so refill on schedule rather than waiting for the taste to come back. After year 3, a chlorine test at a faucet is a good check: once chlorine starts showing up after the filter, it is time.

Refill: 1.5 cubic feet of Centaur: 1 x 1 cu ft bag and 1 x 1/2 cu ft bag. The 1 cubic foot bag is $295 today, so $295 plus the 1/2 bag, which Aidan prices by text. Take the head off and scoop or wet-vac the wet carbon out into heavy trash bags (a full tank is too heavy to tip), rinse the tank, pour in the new carbon, then soak and flush it the same way as the first fill. The tank and head are reused.

Centaur catalytic carbon refill

• How to install a whole house water filter
• Best whole house water filter for chlorine
• Carbon filters for water: the complete guide
• City water treatment guide
• Carbon filter and water softener: do you need both?
• Backwashing vs non-backwashing carbon filters
• What is activated carbon?
• Carbon filter vs reverse osmosis