Keys Backyard Filters
Keys Backyard hot tubs (the Keys Fitness spas sold through warehouse clubs in the 2000s) take one small screw-in cartridge: 4-5/8″ across, 9-3/4″ long, with a molded cone handle on top and a 2″ thread on the bottom. The brand is gone, the filter is not — it is a common size we ship in two brands.
The Keys Backyard filter
One cartridge covers the line. Not sure yours is original? Send a photo of the bottom of the filter through the form below and we will confirm before you order.
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Hot Tub Filters
Keys Backyard Filter – 25 Sq Ft Outside Thread – Single – ProAqua – High Flow
$57.99 Add to cart
✅ Not Sure It Fits? Verify Before Ordering
Hot tub filter fitment varies by spa brand, model, year, filter size, thread style and top/bottom style.
To confirm the correct replacement, send clear photos of:
- The label or end cap of your current filter
- Your spa serial number sticker
- The filter well with the filter removed (so we can see the fitting)
EZ Hot Tub Parts confirms fitment before you order, so you do not pay return freight on a wrong filter.
Keys Backyard filter buying guide
25 sq ft outside thread, cone handle. 4-5/8″ across, 9-3/4″ long, 2″ male pipe thread (Pleatco PGS25P4, Unicel 4CH-24, Filbur FC-0131, Darlly 40260). ProAqua or Darlly, singles and 2 / 4 packs; both drop-ship from US stock. If your old cartridge measures anything else, send a photo through the form above — Keys Backyard is an obsolete brand and a previous owner may have swapped the filter housing.
Other Keys Backyard parts. Keys Backyard spas were built on Balboa control systems; the replacement circuit board for control box 54757 / 53752 / 54344 / 54345 is on the Keys Backyard parts page, and topsides, heaters and sensors are matched from the label inside the equipment door under Balboa parts.
Not sure which filter brand is right for you? Compare Hurricane, OEM Factory Direct, Pleatco, ProAqua, Darlly and Ego3.
Keep your filters working longer: High Pressure Filter Nozzle | Filter Cleaner | Water Care — and every order over $99 ships free, so a spare set plus cleaner usually rides along at no extra cost.
Keys Backyard: Filter (ProAqua) | Filter (Darlly) | Circuit Board 54757 | All Keys Backyard Parts
Keys Backyard filter questions
A 25 sq ft screw-in cartridge, 4-5/8″ across and 9-3/4″ long, with a cone-shaped handle and a 2″ thread on the bottom — Pleatco PGS25P4 / Unicel 4CH-24. We list it in ProAqua and Darlly.
No — Keys Backyard spas have not been made for years, so there is no factory parts channel. The filter is a standard industry size, and the Balboa control parts they were built with are still made; start with the circuit board and Balboa links above.
Yes — a replacement for control boxes 54757, 54757-01, 53752-01/-03, 54344 and 54345 (Balboa VS510SZ) is on our Keys Backyard parts page. It ships with a female Plug-n-Click adaptor; read the notes on that page about the heater connection and the copper strap before ordering.
Every 12 months with a rinse every 2–4 weeks and a monthly soak in filter cleaner; small cartridges load quickly, so a 2 pack to rotate is worth it.