How to Replace Hot Tub Filters (Step-by-Step)

Replace Your Spa Filters Safely

Swapping hot tub filters is one of the easiest maintenance jobs — and one of the most impactful. Fresh cartridges restore jet pressure, help heaters stay on, and cut down on sanitizer demand. Plan 20–30 minutes, work with the power off, and follow these steps to avoid leaks, air locks, and snapped fittings.

What You Will Need

• Replacement cartridge(s) matched to your part number
• Silicone grease for o-rings (spa-safe, not petroleum jelly)
• Garden hose and optional filter cleaner for the old set
• Towels — some water will spill from the canister
• Owner's manual for filter housing location (varies by brand)

Step 1: Turn Off Power

Switch off the spa at the GFCI breaker or disconnect. Do not rely on the topside panel alone — pumps can still kick on during filtration cycles. If you are only rinsing filters quickly without opening plumbing, some owners use "hold" or service mode; for full replacement, full power off is safer.

Step 2: Release Pressure and Open the Housing

Filters usually live under the skimmer basket, in a side canister behind a twist-lock lid, or beneath the equipment door. Open the cover slowly — trapped air can spray water. On threaded housings, unscrew the retaining ring counter-clockwise. Note how o-rings sit so you reinstall them correctly.

Step 3: Remove the Old Cartridge

Lift straight up on most drop-in cartridges. Threaded models unscrew gently — forcing a stuck filter can crack the plastic skirt. Inspect the housing for debris, cracked o-rings, or broken tabs. Replace worn o-rings now; they cost pennies and prevent slow leaks that trip flow sensors.

Step 4: Install the New Filter

1. Rinse new cartridges to remove manufacturing dust — even "ready to use" filters benefit from a quick spray
2. Lightly grease o-rings if your manual recommends it
3. Seat the cartridge fully; it should sit flat without rocking
4. Hand-tighten retaining rings — overtightening cracks plastic threads

If your spa uses two filters, install both before restoring power so both suction lines are covered.

Step 5: Refill, Prime, and Restore Power

Top up water if the level dropped below the skimmer. Turn power back on and run a low-speed circulation cycle for several minutes. Listen for pump cavitation (a gravelly sound) — that often means an air lock. Briefly loosen a pump union to bleed air, then retighten. Most control packs clear flow-related error codes once water moves steadily.

Common Mistakes to Avoid

• Installing the wrong length — water bypasses short cartridges
• Reusing cracked end caps or collapsed pleats to "save money"
• Running the heater with air in the line — can trip high-limit sensors
• Forgetting to reset the filter timer reminder on smart topsides

When to Call for Help

If the housing is cracked, unions strip easily, or error codes return after replacement, stop and book service. A small leak at the filter canister can wick moisture into equipment and cause GFCI trips — our Edmonton team diagnoses those issues daily.