Buy replacement cartridges from the brand that made your shower filter, either on its own website or from a retailer that carries that brand. Find the model name on the unit, in the manual or in your order history first. Cartridges are almost always sold on their own, so you rarely need a new shower head. Don't assume one brand's cartridge fits another brand's housing unless the maker says it does. To work out a year's cost, divide 12 by the months each cartridge lasts, multiply by the price per cartridge, and compare single, multi-pack and subscription prices per cartridge.
Where can I buy a replacement cartridge?
Start with the company that made your filter. Its own website will list the cartridge built for your model, usually with single, multi-pack and subscription options. Retailers that carry the brand may stock the same cartridge, but check that the listing names your exact model and not just the brand.
Things worth checking before you click buy:
- The model name or number. One brand can make several shower filters, and their cartridges often look alike but are different parts.
- Pack size and price per cartridge. A cheap listing can turn out to be a single cartridge, while a pricier one holds three.
- Shipping. On a small order, shipping can add a real share of the cost.
Are cartridges sold separately, or only with a new shower head?
Almost always separately. A filtering shower head is built so you replace the cartridge inside it and keep the head, the same way you keep a fridge and swap its water filter. If a brand only sells its filter as part of a whole new head, count that into your yearly cost before you buy, because it will be much higher.
Will a cartridge from one brand fit another brand's shower head?
Don't count on it. Shower filter cartridges are made for a specific housing: their length, width, seals and which end goes up all differ from maker to maker. A cartridge that almost fits can leak, let water flow around the filter media rather than through it, or leave the head hard to close.
Some third-party sellers describe their cartridges as compatible with another brand. Unless the brand that made your head confirms that, treat the claim with care. If water goes around the media rather than through it, the filter isn't doing its job, and you can't tell that from looking at the spray.
How do I check which cartridge my filter takes?
- Look at the unit. Many heads have the model name printed on the body, the handle or the filter housing.
- Check the manual or the box. The replacement part is usually named there.
- Look at your order history. Your original order email or account page will name the product you bought.
- Ask the brand. A photo of your head sent to customer support usually settles it fast.
A handheld and a fixed head from the same brand often take different cartridges, so match the exact product, not just the brand.
How often should a shower filter cartridge be replaced?
Follow the maker's recommended interval. It's the number your yearly cost depends on, and it's based on how the filter media wears out. In our filters the Vitamin C oxidizes as it works, which is why we give a set replacement period instead of waiting for a visible sign. In our own testing, KDF-55 cartridges also lost chlorine reduction as the cartridge aged. Whatever is inside, a cartridge that is still in the head isn't necessarily still doing its job.
Two signs that mean replace it early: the water pressure drops noticeably, or the filter looks deep brown or black.
Color isn't a gauge, though. A filter that has darkened isn't telling you how much chlorine it removed or how much life it has left, and a pale one isn't proof it is still working. You can see what used filters from real homes look like on our proof page[3]. Use the calendar, not the color.
How do I work out what a year of cartridges costs?
Two steps:
- Cartridges per year = 12 divided by the months between replacements (use the recommended interval, not the longest a cartridge could last).
- Yearly cost = cartridges per year multiplied by the price per cartridge, plus any shipping.
So a cartridge you replace every month means 12 a year, and one you replace every two months means 6. If you're still choosing a filter, add the price of the head to get your first-year total. That gives you a fair way to compare a cheap head with costly refills against a pricier head with cheap refills.
One catch: work out the price per cartridge. Multi-packs and subscriptions often cost less per cartridge, so divide the pack price by the number of cartridges before comparing.
Is a bundle, a single cartridge or a subscription cheaper?
Per cartridge, multi-packs and subscriptions usually come out ahead of single orders. A subscription has a second benefit that matters just as much: the cartridge arrives on time, so you aren't stretching an old one for weeks because you forgot to reorder. Look for plans you can skip, pause or cancel without fees, and check whether shipping is included.
A one-time order makes sense if you shower less often than average, are trying a filter out, or just want to choose when to reorder.
How do I swap the cartridge, and what do I do with the old one?
Follow the manual for your model. The step people most often get wrong is putting the cartridge in upside down. For our filters:
- Showerhand filter: micron end up, Vitamin C gel end down. It has no rubber ring.
- Showerhead filter: rubber ring side down, sticker side up.
For the old cartridge, check the disposal note in your manual or on the brand's site, and your local trash and recycling rules. Don't assume the plastic housing can go in curbside recycling. Rules differ by town.
What our refills cost, and what a shower filter does not do
A shower filter is there to deal with the disinfectant your utility adds: chlorine or chloramine. It does not soften water or remove hardness (calcium, magnesium). A water softener does that. If your concern is scale on the glass, a new cartridge won't change it.
We use an NSF/ANSI 42 certified filter*. In independent lab testing, our filter removed 99.9% of chlorine and chloramine. In our own testing that 99.9% held through Day 1 to 60 of cartridge life in the Showerhead and through Day 1 to 30 in the Showerhand, so our recommended replacement dates fall inside that window.
The Second Showerhead is $99, or $79 when bought with a filter plan, and The Second Showerhand is $89, or $69 with a plan. One filter included with each. Refills are sold separately, and each fits only its own device:
| Showerhead | Showerhand | |
|---|---|---|
| Refill pack | 2-pack: $39 one time, $36 on subscription[1] | 3-pack: $29 one time, $27 on subscription[2] |
| Each filter lasts | 2 to 3 months | 1 to 2 months |
| We recommend a new one | Every 60 days | Every 30 days |
| Subscription ships | Every 4 months | Every 3 months |
| Filters per year on subscription | $72 to $108 | $81 to $108 |
| Year 1 total on subscription (device + filters) | $151 to $187 | $150 to $177 |
Plan filters ship free before they're due, and you can skip, pause or cancel anytime with no fees. The device warranty is 1 year, and it lasts for life while a filter subscription is active. One-time orders ship free at $40 or more ($6.99 below).
*Micron PP sediment filter certified by NSF/ANSI 42 standards.
FAQ
Can I wait until the filter changes color to replace it?
No. A filter's color doesn't show how much life is left or how much chlorine it is removing. Replace it when the recommended period is up, or sooner if it looks deep brown or black or the water pressure drops noticeably.
Do Second Shower filters fit other brands' shower heads?
Our refills are made for our own devices: the 2-pack fits The Second Showerhead and the 3-pack fits The Second Showerhand. The two refills aren't interchangeable with each other either, so order the one that matches your device.
Does a new cartridge come with the shower head?
With ours, yes: one filter included, already installed in every device. After that, you buy refills as a one-time pack or on a subscription.
Will replacing my shower filter fix hard water spots?
No. A shower filter cartridge doesn't remove hardness (calcium and magnesium), and Second Shower doesn't soften water. A whole-house ion-exchange water softener is what removes hardness.
How often should I replace a Second Shower filter?
We recommend a new Showerhead filter every 60 days (each lasts 2 to 3 months) and a new Showerhand filter every 30 days (each lasts 1 to 2 months). The Vitamin C oxidizes as it works, which is why we go by the calendar.
