Backwashing vs Non-Backwashing Carbon Filters: Which Do You Need?

Both types use the same Centaur catalytic activated carbon media, so the choice is not about which one cleans the water better. About 95% of the time I recommend the non-backwashing tank, and on city water it is the only one you need. The backwashing tank earns its drain line, its outlet and its higher price only when sediment, dirt or fine clay in your water would get trapped in the carbon.

Caller "If I were to go with a backwashing carbon tank, would that extend the life of the carbon at all?"

Aidan "No, not really. The only time we recommend backwashing is if you're putting it in and there's other issues in the water, like heavy, heavy sediment."

A well owner in Delaware asked me that in April. This page is the long version of my answer.

My two-minute video answer

I answer the nine questions people ask before they choose, one after another.

One correction to the drawing at 0:28: it shows gravel in the bottom of the tank. Every carbon tank we sell has a Vortech plate there instead of gravel.

What backwashing does to a carbon bed

Backwashing reverses the water to rinse trapped dirt out of the carbon and down a drain. In a backwashing tank the water normally flows down through the carbon, and sediment gets trapped on top of the carbon or works its way down into it. As I put it in the video: "Backwashing actually lifts the carbon because it's light, and the way the Vortech plate works, it spins the water around in a circular direction," which carries the dirt out the backwash drain.

A non-backwashing tank is also called an upflow tank, because the water flows up through the carbon on its way to the house. It never rinses itself, so it needs no drain and no power. Every carbon tank we sell, backwashing or not, is a Vortech tank: a plate at the bottom spreads the water across the tank, with no gravel.

Choosing an acid neutralizer instead? That is a different answer, on its own page: backwashing or non-backwashing acid neutralizer.

Which carbon tank your water needs

Get the non-backwashing tank for city water and for most wells. Get the backwashing tank only if sediment, dirt or fine clay comes through your well water.

Carbon tanks for a rotten egg smell

A sulfur smell does not mean you need the backwashing carbon tank. For an average smell I recommend the 2.5 cubic foot non-backwashing tank, which uses catalytic carbon that "works really well for average levels of sulfur," and as I told that caller, "it doesn't have to backwash." When the smell is strong, a carbon tank "may not last very long," and I point people to a sulfur filter with Katalox Light media instead. That one is a backwashing filter, but it is not a carbon tank. If you have a hydrogen sulfide number, what your hydrogen sulfide level means covers which treatment each level needs.

On a well you have never tested, the certified well water test ($199) shows your iron and manganese, which decide whether an iron filter goes in ahead of the carbon. It does not measure the rotten egg gas; that one you go by smell.

City or well, sediment or smell

Text me about your water

Tell me if you are on city water or a well, and whether you see sediment or smell sulfur. I will tell you which tank fits.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

What a backwashing carbon tank needs

A backwashing tank needs a drain, an outlet and strong flow from your well. Its valve will also need parts as it ages. As I say in the video, "It needs a drain, it needs electricity, and it's much more difficult to install and you have to deal with valve parts going bad over time." The non-backwashing tank needs none of that.

The flow matters as much as the drain. In the video: "If you don't have enough to properly backwash the carbon tank, it's better to go with a non-backwashing system." And valves do not last forever: "15, 20 years down the road, doesn't matter what type of valve you have, it's gonna need some maintenance."

Which carbon bed lasts longer

The non-backwashing carbon lasts longer, because it is never put through a backwash. In the video I said, "I'd say the non-backwashing because you don't have to backwash it," and the backwash flow puts the carbon under more stress. A backwash does not give the carbon its life back, either. As I told the caller in Delaware, carbon is an absorbent: "Once it's pulled in, it doesn't come back out until the carbon bed becomes completely exhausted."

On a typical household I tell people about 5 years before the carbon is replaced: "You probably get 4 years out of the 1.5, maybe 5, and you'll get 5 to 6 years out of the 2.5 before you have to change out the carbon." When it is time, you dump the old carbon into trash bags and pour in new. Centaur carbon is $295 per cubic foot.

Where sediment does come through, the backwash is what keeps the carbon working. Without it, the dirt stays trapped in the bed.

What each carbon tank costs

The non-backwashing tank costs $400 less at 1.5 cubic feet and $800 less at 2.5. It also costs less to run: no power for a valve, no water down a drain, no valve parts later. In the video: "all backwashing systems are much more expensive than a non-backwashing system."

Prices include shipping to the lower 48 states. The 2.5 cubic foot non-backwashing tank is the one I have in my own house. All four tanks are on the non-backwashing carbon filters and backwashing carbon filters pages.

What comes with each carbon tank

Every tank ships empty. The carbon comes in separate bags and is loaded into the tank at install. What ships: the tank, the control valve with a bypass valve, the carbon in bags and a fill funnel. Fittings are not included, and for the backwashing tank neither is the 1/2 inch drain tubing.

We recommend installation by a licensed plumber, and I support your plumber by phone at 800-460-5810. The non-backwashing tank is two water connections. The backwashing tank adds the drain line and needs an outlet near the valve.

Frequently asked questions