How to Drain and Refill Your Hot Tub for Crystal Clear Water

Why it matters

Maintaining a hot tub is more than just balancing the pH. Over time, the water becomes saturated with dissolved solids (TDS), such as salts, lotions, body oils, and chemical byproducts. When the TDS level gets too high—typically above 1,500 ppm—the water loses its ability to stay chemically balanced.

Draining and refilling your hot tub ensures:

• Sanitizer Efficiency: Fresh water requires fewer chemicals to maintain a safe environment.
• Equipment Longevity: High mineral buildup can cause scale on the heater element and wear down pump seals.
• Water Clarity: It removes the organic "bio-burden" that causes foaming and cloudiness that chemicals can no longer fix.
• Skin Health: Periodic refreshing of the water prevents the itchy "hot tub rash" caused by bacteria that shield themselves in biofilm.

How often

As a general rule, you should drain and refill your hot tub every 3 to 4 months.

If you use your hot tub frequently (3 or more times per week) or have many guests, you may need to do it every 2 months. A quick formula to determine your specific schedule is to divide your hot tub’s gallon capacity by 3, then divide that result by the average daily bather load.

Signs you shouldn't wait:

• Water remains cloudy even after a "shock" treatment.
• The water has an unusually strong chemical or "musty" smell.
• You are struggling to stabilize the pH or alkalinity.
• There is visible white or green scale on the shell or jets.

What you need

• Submersible sump pump: (Optional but recommended) This speeds up the process significantly, taking 20–30 minutes vs. several hours via the gravity drain.
• Garden hose: Long enough to reach a safe drainage area.
• Line flush cleaner: To remove biofilm from the internal plumbing.
• Non-abrasive sponge or microfiber cloth: For wiping the shell.
• Hot tub shell cleaner: Or a simple mixture of white vinegar and water.
• New or clean filter: This is the best time to rotate or deep-clean your filters.
• Fresh water source: A standard outdoor faucet.

Step-by-step

Follow these steps to ensure you don't damage your heater or pump during the transition.

1. Flush the lines

Before turning off the power, add a "line flush" or "jet cleaner" product to the old water. Turn on the jets and let the product circulate for at least 30 minutes (or according to package directions). This breaks down the oily biofilm inside the pipes that you can't reach by hand.

2. Disconnect the power

Crucial: Switch off the circuit breaker at the GFCI panel. Never drain a hot tub with the power on, as the pumps or heater could activate without water, causing permanent damage.

3. Drain the water

• Gravity Drain: Locate the drain valve (usually at the base or behind the side panel). Attach a garden hose and open the valve. This can take several hours depending on the size of the tub.
• Submersible Pump: Place the pump at the deepest point of the footwell, attach a hose, and plug it into a remote outlet away from the water. This is much faster.

Note: Ensure you are draining the water into a proper sewer clean-out or a neutral landscape area. Avoid draining directly onto sensitive plants or into storm drains if local laws prohibit it.

4. Clean the shell and filters

Once empty, use a soft cloth and a dedicated hot tub shell cleaner to wipe down the acrylic. Focus on the "scum line" around the top. Rinse the residue toward the drain and use a wet/dry vac to suck up the last few inches of dirty water. Remove the filters and either replace them or soak them in filter cleaner.

5. Inspect the hardware

While the side panels are off or the tub is empty, do a quick visual check. Look for signs of small leaks at the pump unions or cracks in the jet faces.

6. Refill the hot tub

Important: Do not simply stick the hose into the footwell. Place the garden hose directly into the filter compartment. This forces water through the internal plumbing first, pushing air out of the system and preventing an "air lock" when you restart the pumps. Fill until the water level reaches the midpoint of the skimmer or the line indicated by the manufacturer.

7. Power up and balance

Turn the breaker back on. Once the system primes, set your desired temperature. Add your startup chemicals (metal sequestrant, alkalinity increaser, pH balancer, and sanitizer) in that order. Wait for the water to reach at least 80°F before testing and making final chemical adjustments.

When to call a pro

Cleaning a hot tub is a standard DIY task. However, you should call a technician if:

• You see "black flakes" in the water after flushing, which may indicate mold in the internal gaskets.
• The pump makes a high-pitched squealing noise upon restart (bearing failure).
• The GFCI breaker trips immediately after refilling.
• You find significant puddling inside the equipment cabinet.

Safety

• Electricity: Always verify the power is off at the breaker before reaching into the equipment cabinet or starting the drain.
• Chemical handling: Wear gloves when handling concentrated "line flush" or chlorine/bromine during the refill.
• Slipping: The acrylic shell is extremely slippery when wet and soapy. Do not climb inside the tub to clean it unless you have non-slip footwear and a stable handhold.
• Drainage: Be aware of where 400+ gallons of water are going. Avoid flooding your neighbor’s yard or your own crawlspace.

Cost

The cost of a DIY drain and refill is relatively low, primarily consisting of the chemicals used.

• Line Flush/Cleaner: $15–$25 per bottle.
• Water Cost: $5–$15 depending on local utility rates and tub size (usually 300–500 gallons).
• Replacement Filters: $30–$60 (required every 12–24 months).
• Submersible Pump (One-time buy): $50–$100.

If you hire a professional service to perform a "valet" or "drain and clean" service, expect to pay $150 to $300 per visit, depending on your location and the complexity of the tub.