How Often Should You Drain And Refill A Hot Tub?

Regular draining and refilling keep your hot tub water fresh, clean, and safe. While proper chemical maintenance handles daily water quality, complete drainage addresses the gradual buildup of dissolved solids that even the best sanitization can’t eliminate. 

Understanding when and why to drain your hot tub helps you maintain optimal water conditions and protects your investment.

What Is The Standard Drain Cycle For Hot Tubs?

Most hot tub owners should plan to drain and refill every 3-4 months under average usage conditions. This timeline provides a practical starting point, but your specific situation may require more or less frequent draining depending on several factors.

The Drain Calculation Formula

A simple formula helps determine your optimal drain schedule based on actual usage:

• Hot tub gallons ÷ daily bathers ÷ 3 = days between drains
• For example, a 400-gallon hot tub used by two people daily would follow this calculation:
• 400 ÷ 2 ÷ 3 = 67 days (approximately every 2 months)
• The same hot tub used by one person daily would extend to:
• 400 ÷ 1 ÷ 3 = 133 days (approximately every 4 months)

This formula accounts for the reality that more bathers introduce more contaminants, requiring more frequent water refreshes.

Why Do Total Dissolved Solids Require Complete Draining?

Total dissolved solids, or TDS, accumulate in your hot tub water over time despite maintaining proper chemical balance. Every time you add chemicals, minerals from source water, or contaminants from bathers, these substances dissolve into the water. Unlike particulate matter that filters can remove, dissolved solids stay in solution permanently.

Understanding TDS Saturation

Fresh tap water typically contains 200-500 ppm of dissolved solids. As you maintain your hot tub, this number climbs steadily. Sanitizers, pH adjusters, alkalinity increasers, and other treatment chemicals all contribute dissolved material. Body oils, lotions, perspiration, and other organic matter add to the load.

When TDS reaches 1500-2000 ppm, the water becomes saturated. At this point, several problems emerge:

1. Sanitizers lose effectiveness because the water can’t properly dissolve additional chemicals. Your chlorine or bromine readings may appear normal, but their actual sanitizing power diminishes significantly.
2. Water feels different on your skin. Many people describe high TDS water as “heavy,” “thick,” or “slippery.” The sensation indicates the water has absorbed its maximum capacity of dissolved substances.
3. Foam develops persistently even with proper chemical balance and anti-foam treatments. The dissolved solids create surface tension changes that promote foaming regardless of contaminant levels.
4. Chemical adjustments become increasingly difficult. You’ll find yourself adding more products to achieve smaller changes in water parameters.

What Seasonal Considerations Affect Drain Timing?

The time of year influences when you should schedule your drain and refill to prevent problems and maximize benefits.

Fall Draining For Winter Protection

If you live in an area with freezing temperatures, draining your hot tub before winter provides critical protection against freeze damage to plumbing lines. Even hot tubs that continue operating through winter benefit from a fall refresh that removes accumulated summer contaminants before cold weather sets in.

For hot tubs that will be winterized and shut down, complete draining followed by proper line purging prevents water from freezing inside pipes and causing expensive damage. The expansion of frozen water can crack plumbing components, split pump housings, and destroy valves.

Spring Refreshing After Winter

Spring represents an ideal time for draining even if you used your hot tub throughout winter. Cold weather operation often leads to chemical buildup as you maintain higher sanitizer levels to combat reduced effectiveness in colder water. A spring drain removes this accumulation and starts the active outdoor season with fresh water.

For winterized hot tubs, spring draining and refilling prepares the system for renewed use while allowing you to inspect all components after months of inactivity.

What Signs Indicate You Need To Drain Immediately?

Several warning signs demand immediate draining regardless of your normal schedule. These indicators suggest your water has reached a point where continued treatment won’t restore proper conditions.

Inability to Balance pH

When you can’t stabilize pH despite having proper alkalinity levels, your water has likely reached TDS saturation. You add pH decreaser and the levels drop temporarily, then quickly rise again. Or pH increaser has minimal effect despite repeated additions. This instability indicates the water can no longer properly respond to chemical adjustments.

Persistent Cloudiness After Shocking

Cloudy water that remains murky even after proper shocking and adequate filtration time signals serious problems. If your water doesn’t clear within 24 hours of shocking with proper chemical levels and clean filters, the cloudiness likely stems from excessive TDS rather than contamination.

Odors That Indicate Biofilm

Musty, earthy, or sewage-like odors that persist despite proper sanitizer levels point to biofilm formation in your plumbing lines. Biofilm creates protective colonies where bacteria hide from sanitizers. Once established, biofilm requires complete system purging and draining to eliminate.

Even sweet or chemical odors can indicate problems. These smells often develop when combined chloramines or bromamines build up to levels that shocking can’t address. Complete water replacement becomes necessary.

Foam That Won’t Disappear

Occasional foam from body oils or lotions is normal and easily managed. Persistent foam that returns immediately after dissipating, even with proper chemical balance and anti-foam products, indicates high TDS levels that only draining can resolve.

What Is The Complete Drain And Fill Process?

Proper draining involves more than simply emptying your hot tub. A systematic approach ensures you address all maintenance needs while the tub is empty.

Line Flushing Before Draining

Before you drain, flush your plumbing lines to remove accumulated biofilm and organic buildup. Add a line flush product to your water and run all pumps and jets for the recommended time, typically 15-30 minutes. This treatment dislodges hidden contamination that normal filtration misses.

The flushing process is crucial because biofilm hides in plumbing lines where regular sanitizers can’t reach. Even with proper chemical maintenance, this buildup accumulates over months of use. Flushing before draining ensures you remove these contaminants rather than leaving them to contaminate your fresh water.

Draining Procedure

Once flushed, drain your hot tub completely using either the drain valve or a submersible pump for faster removal. Pumps significantly reduce draining time, especially for larger hot tubs. As the water level drops, use towels or a wet/dry vacuum to remove remaining water from footwells and seat areas.

Filter Deep Cleaning

With the tub empty, remove all filters and perform deep cleaning. Rinse thoroughly with a garden hose to remove loose debris, then soak in filter cleaning solution according to product instructions. This typically requires 8-24 hours of soaking to break down oils and minerals that accumulate in filter media.

Consider replacing filters if they show signs of wear, permanent discoloration, or if they’re approaching 12-24 months of use. Clean filters work more efficiently and reduce strain on your pump.

Shell Cleaning

Clean the empty shell with products specifically designed for hot tub surfaces. Avoid abrasive cleaners that can scratch or damage the acrylic finish. Use a soft cloth or sponge to remove waterline buildup, stains, and any residue.

Pay special attention to jets, removing the jet faces if possible to clean behind them where buildup often accumulates. Wipe down the headrests, pillows, and any other accessories.

Inspect the shell carefully while it’s empty. Look for cracks, blisters, or other damage that may require repair before refilling.

Refilling Properly

When refilling, place your garden hose through the filter compartment rather than directly into the shell. This approach reduces air lock problems in your plumbing system. Fill to the proper level as indicated in your owner’s manual, typically just below the bottom of the pillows.

Once filled, add your startup chemicals according to your water care system requirements. Test and adjust as needed before using your hot tub.

What Common Mistakes Should You Avoid?

Several frequent errors undermine the benefits of draining or create new problems.

Partial Drains Don’t Reset TDS

Some hot tub owners attempt to extend their drain interval by removing 25-50 percent of the water and replacing it with fresh water. While this dilutes TDS levels temporarily, it doesn’t effectively reset the dissolved solids count.

Think of it like trying to freshen up old coffee by adding new coffee to the pot. You’re just creating a larger volume of mediocre liquid rather than starting fresh. Complete drainage is the only way to truly address TDS accumulation.

Skipping Line Flushing

Draining without first flushing your plumbing lines leaves biofilm and organic buildup intact. When you refill, these contaminants immediately begin affecting your fresh water. You’ll find yourself fighting water quality issues much sooner than expected because you didn’t address the hidden contamination in your plumbing.

Using Harsh Cleaners On The Shell

Abrasive cleaners, household bleach, or other harsh chemicals can damage your hot tub shell. These products may remove stains temporarily but cause long-term damage to the acrylic finish. Always use products specifically formulated for hot tub shells that clean effectively without causing harm.

Keep Your Hot Tub Water Fresh With WCI Pools And Spas

Understanding drain timing helps you maintain crystal clear water and optimal hot tub performance. Whether you follow the standard 3-4 month schedule or use the calculation formula for your specific usage, regular draining addresses problems that daily maintenance can’t solve.

At WCI Pools & Spas, our team provides comprehensive support for all your hot tub maintenance needs. We offer water testing, troubleshooting guidance, and professional service for those who prefer expert assistance with maintenance tasks, including draining and refilling.

Visit WCI Pools & Spas For Hot Tub Maintenance Support:

Contact us today for personalized maintenance guidance, quality water care products, or professional service. Our knowledgeable team helps Iowa hot tub owners enjoy clear, clean water and maximum relaxation from their investment.