How Often Should You Drain and Refill Your Hot Tub

Quick answer: Drain and refill your hot tub every 3 to 4 months, or sooner if total dissolved solids exceed 1,500 ppm or the water develops persistent odor, foam, or cloudiness that chemicals cannot resolve.

Why Draining Your Hot Tub Matters

Every time you use your hot tub, you introduce dissolved solids into the water. Body oils, sweat, lotions, deodorant residue, and laundry detergent left on swimsuits all accumulate over time. Your sanitizer breaks these contaminants down, but the dissolved byproducts remain. Chemical treatments can only do so much before the water becomes saturated.

Think of it like reusing the same bathwater for months. No amount of soap makes that appealing. Hot tub water follows the same principle. Once total dissolved solids (TDS) climb too high, chlorine and bromine lose effectiveness, pH becomes difficult to stabilize, and the water takes on a dull, lifeless appearance.

Regular draining resets your water chemistry to a clean baseline. It removes accumulated minerals, chemical byproducts, and microscopic debris that your filter cannot capture. This single maintenance task extends the life of your pump, heater, jets, and shell more than almost anything else you can do.

The Standard 3-to-4-Month Schedule

Most manufacturers recommend draining every 3 to 4 months for a hot tub used by 2 to 4 people several times per week. If you use your hot tub daily or host frequent guests, drain every 2 months. If you soak alone once or twice a week, you might stretch to 5 months.

A simple formula: divide the total gallons by the number of daily bathers, then divide by 3. For a 400-gallon tub used by 2 people daily, that is about 67 days or just over 2 months.

Signs You Need to Drain Sooner

• Persistent foam: When defoamer stops working within hours, the water is saturated with dissolved organics.
• Cloudy water despite balanced chemistry: If pH, alkalinity, and sanitizer are in range but water looks hazy, TDS is the culprit.
• Strong chemical smell: A harsh chlorine odor means chloramines have built up. These are spent sanitizer molecules that irritate skin and eyes.
• pH swings wildly: Dissolved minerals buffer the water unpredictably despite proper alkalinity.
• Sticky waterline: Biofilm forming at the waterline means organic contamination beyond what sanitizer can handle.
• TDS above 1,500 ppm: Anything above 1,500 ppm over your fill water baseline is a clear signal to drain.

How to Drain and Refill Properly

Before draining, run a plumbing purge product through the system for 20 to 30 minutes on high jets. This breaks up biofilm inside pipes and jets. Then drain completely.

While empty, wipe down the shell with a non-abrasive cleaner. Pay attention to the waterline and jet faces. Rinse the filter or replace it if older than 12 months.

When refilling, place the hose into the filter housing or skimmer to fill plumbing from the inside out, preventing air locks. After filling, run jets briefly to clear air bubbles.

Balance chemistry in order: alkalinity (80-120 ppm), pH (7.2-7.8), calcium hardness (150-250 ppm), then sanitizer. Adding AquaDoc Natural Spa Enzyme helps prevent organic buildup from restarting.

Protecting Your Hot Tub Between Drains

Shower before soaking to reduce contaminants. Use a weekly treatment like AquaDoc 3-in-1 Spa Care to keep organics in check. Protect your cover with AquaDoc Cover Care to prevent debris and UV damage.

Test water twice per week. The CDC hot tub safety guidelines recommend maintaining consistent sanitizer levels to prevent bacterial growth between water changes.

Frequently Asked Questions

Can I just keep adding chemicals instead of draining?

No. Chemicals treat contaminants but cannot remove dissolved solids. TDS accumulates regardless of maintenance quality. Eventually the water becomes too saturated for sanitizer to work.

Is it bad to drain in winter?

You can, but work quickly to prevent plumbing from freezing. Drain, clean, and refill in the same session. Keep the heater running during refill if temperatures are below freezing.

Should I replace the filter every time I drain?

Not necessarily. Filters last 12 to 18 months. Deep clean with a filter soak each drain. Replace when pleats are frayed or compressed flat even after cleaning.

Does hard water mean I drain more often?

Yes. Fill water above 200 ppm calcium hardness means minerals accumulate faster. Hard water areas may need draining every 2 to 3 months. A hose pre-filter helps reduce incoming minerals.