Single replacement Caldera Spas filter (100 sq ft open bottom) — Darlly
Fits select Caldera Spas models that use the 100 sq ft open bottom cartridge. Caldera Spas used more than one filter size over the years, so match the diameter, length, and top and bottom style below to the filter you are replacing — or send us a photo and we will confirm before you order.
Not sure which filter brand is right for you? Compare hot tub filter brands here.
Did you know the number one reason for hot tub freeze damage is a dirty filter? Dirty filters also cause additional stress on the pump/motor and leads to premature failure.
Proper Filter Care System:
- Have 2 sets of filters
- Install clean filter
- Rinse dirty filter with high pressure nozzle
- Verify no debris left between pleats, before storing on shelf to dry
- Once a month soak filters in a filter cleaner solution
Filter Specs:
- Diameter – 8″
- Length – 16-1/2″
- Top: Handle
- Bottom: Open w/Lip Seal
- SQFT: 100
What’s in the box: one filter cartridge.
✅ Not Sure It Fits? Verify Before Ordering
Hot tub part compatibility can vary by spa brand, model, year, serial number, control system, and part revision.
To help us identify the correct replacement part, please send clear photos of:
- Your existing part label or sticker
- Your spa serial number sticker
- The equipment area or installation location (if accessible)
EZ Hot Tub Parts can help confirm fitment before you order and help reduce costly returns.
It fits the Caldera Spas models that use a 100 sq ft open bottom cartridge measuring 8″ in diameter and 16-1/2″ long. Measure your old filter end to end and across the end cap — if the numbers match, it fits. Still unsure? Use the fitment form above and send a photo of your filter.
Measure the diameter across the end cap and the total length from end to end, then check the top (open, closed, handle) and the bottom (open, threaded, slip fit). This cartridge is 8″ x 16-1/2″, top: handle, bottom: open w/lip seal.
This cartridge cross-references to: Darlly 81004, Pleatco PCD100W, Filbur FC-3965, Unicel C-8399, 17-175-1141, Caldera 1039607, XLS-853, P-8399.
This is a Darlly replacement cartridge. Compare it with the other filter brands we carry on our filter brand comparison page.
Rinse it every 2–4 weeks, deep-clean it monthly with filter cleaner, and replace it every 12–24 months or sooner if the pleats are torn, flattened, or the end caps are cracked. Keeping two sets and rotating them makes each set last longer.
A second set means you always have a clean, dry filter ready to drop in while the other set soaks. Multi-packs also cost less per filter than buying singles.
17-777-1141 PA-1899 Darlly 81004 Pleatco PCD100W Filbur FC-3965 Unicel C-8399 17-175-1141 Caldera 1039607 XLS-853 P-8399
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