The standard advice for traditional hot tubs is a full drain every 3–4 months. With an Eco Spa and its non-porous HDPE shell, you typically replace the water every 10 months to a year — that's the interval we run on our own tub. Here's how to know when it's actually time, and how to do the drain properly.
Acrylic shells roughen at the surface over time — bacteria have something to colonize, biofilm builds up, and the water degrades faster regardless of chemical maintenance. HDPE is molecularly smooth, so bacteria struggle to grip it; any bacteria in the water came off you, not off the shell. Back that up with overkill filtration — 100 ft across two large filters as standard — and the water stays usable far longer with very little chemical input, which is what lets you stretch the interval out to 10 months or more. The optional Ecozone ozone upgrade cuts the chemistry even further.
The 5 Signs It's Time to Change the Water
Forget the calendar. These signals tell you the water has reached its limit, regardless of how many months have passed:
- Cloudy water that won't clear. If your water looks dull or murky after a shock treatment and 24 hours of filtration, the total dissolved solids have built up past the point where chemicals can correct it. Drain and refill.
- Persistent foam or scum on the surface. Some foam after heavy use is normal. Foam that persists after jets are off, or scum that reappears within hours of cleaning the waterline, indicates a water chemistry problem that chemical treatment alone won't resolve.
- Unpleasant or unusual odours. A properly maintained hot tub should have a faint clean smell at most. A musty, chemical, or ammonia odour means the water needs to go.
- Chemical imbalance that won't hold. If you're adding chemicals and the pH, alkalinity, or sanitizer levels won't stabilize and hold for more than a day or two, the water is saturated with dissolved solids and needs replacement.
- Over one year since the last change. Even with perfect HDPE chemistry management and low usage, water over one year old should be replaced as a standard practice.
The 6-Step Drain Process
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01
Flush the plumbing. Add a line flush product (available at any hot tub supply store) and run the jets for 30–60 minutes before draining. This clears biofilm from the pipes and jets.
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02
Power off. Turn off the heater and pump before draining. Never run the pump dry.
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03
Drain. Use the drain valve (gravity drain) or a submersible pump for faster drainage. A standard residential drain takes 30–90 minutes with gravity, 10–20 minutes with a pump.
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04
Wipe the sides down. With the HDPE shell you just spray the sides with vinegar and water — no draining and scrubbing the sidewalls the way you would with acrylic. No abrasive cleaners needed; they're unnecessary and can leave residue.
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05
Rinse and refill. Refill with a garden hose. Use a pre-filter on the fill hose if your municipal or well water is hard (a common condition in Prairie provinces).
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06
Balance chemistry and heat. Test and balance pH, alkalinity, and calcium hardness before adding sanitizer. Heat to temperature. Test again after 24 hours before soaking.
Tips to Extend the Interval
- Shower before entering. Body oils, cosmetics, and residue from skin care products degrade water quality faster than almost anything else. A quick shower removes most of it.
- Keep the cover sealed. An open cover lets debris and contaminants in and heat out. When not in use, it should always be closed and locked.
- Rinse filters monthly. A clean filter handles more dissolved solids before needing a full chemical soak.
- Let the non-porous shell and filtration do the work. Every Eco Spa runs 100 feet of filtration as standard, which reduces sanitizer demand and slows the buildup of byproducts that degrade water quality. The optional Ecozone ozone upgrade cuts that demand even further.
- Rinse swimwear before entering. Detergent residue from laundering creates foam and depletes sanitizer faster than almost anything.