Ask five hot tub dealers how often to change the water and you will get the same answer: every three to four months. It is a reasonable default. It is also a number that ignores almost everything that actually determines when your water is finished.
What Really Drives Water Life
Hot tub water does not go bad on a calendar. It goes bad when total dissolved solids build up past the point where chemistry can still do its job. Everything that goes into the tub and does not come out again adds to that total: sanitiser by-products, minerals from your fill water, body oils, lotions, detergent residue from swimsuits.
Which means the real variables are:
- Bather load. Two people a few times a week is a completely different load from six people every weekend. This is the single biggest factor.
- How hard the sanitiser is working. Every gram of chlorine that gets consumed leaves something behind. A system that oxidises contaminants rather than holding a heavy chemical residual accumulates dissolved solids more slowly.
- Fill water hardness. Municipal water on Vancouver Island varies. Harder source water starts you further along the curve on day one.
- Filtration. A tub cycling water through filtration more times per day removes suspended material before it becomes a chemistry problem.
The Signs, Which Beat the Calendar
Your tub will tell you before the date does. Watch for:
- Sanitiser that will not hold. You dose, you test an hour later, it is gone again.
- Foam that keeps returning after you treat it.
- Water that looks dull or slightly cloudy and does not clear with filtration.
- A flat, chemical smell that is not the clean smell of properly balanced water.
Any two of those together means drain it, regardless of how long it has been.
How to Do the Change Properly
- Stop sanitising several days ahead. Let the level fall so the discharge is safe for your yard.
- Run a plumbing cleaner if it has been a while. Biofilm lives in the pipework, not just the water. Draining without flushing the lines just reseeds the fresh fill.
- Cut the power before you drain. A heater that runs dry is an expensive mistake.
- Drain, then wipe the shell. On a non-porous surface this is a rinse and a wipe. On a porous one it takes more work, and it never quite comes fully clean, which is the argument for the material in the first place.
- Clean or replace the filter. Refilling over a loaded filter undoes the whole exercise.
- Refill through the filter housing. This pushes air out of the plumbing instead of trapping it in the pump.
- Balance before you heat. Get alkalinity and pH right on cold water, then bring it up to temperature.
Why the Shell Material Changes This Job
An acrylic shell is porous at a microscopic level. Bacteria colonises the surface, and no amount of scrubbing fully removes it, which is why an acrylic tub tends to need water changes on the shorter end of the range as it ages. The HDPE surface in an Eco Spa is non-porous, so there is nowhere for biofilm to establish itself on the shell. Wipe, rinse, refill.
Paired with Ecozone doing the heavy oxidising, the practical result is that dissolved solids climb more slowly and the tub stretches further between changes. Our team sets up a maintenance template with you at delivery based on how you actually use the tub, rather than handing you a generic chart.
One Thing People Get Wrong
Topping up is not changing. Evaporation removes water and leaves the dissolved solids behind, so a tub that gets topped up all summer is concentrating, not diluting. Top-ups keep the level right. They do not reset the clock.
Questions about your own tub and your own water? Ask us, or read the monthly routine.
A Realistic Schedule by Household
If you want a number to start from rather than a rule to obey, work from bather load. The figures below assume a tub that is filtering properly and holding a sanitiser reading between changes.
| Use pattern | Typical starting interval | Watch for |
|---|---|---|
| Two people, a few soaks a week | Four to six months | Fill water hardness building up |
| Family of four, most days | Three to four months | Foam returning after treatment |
| Regular guests, weekend groups | Two to three months | Sanitiser that will not hold |
| Seasonal or vacation property | Change on arrival and departure | Stagnation between visits |
Adjust from there based on what the water tells you rather than the calendar. If you hit the interval and the water still balances easily, holds a reading and looks clear, you have room to stretch it. If you are fighting the chemistry two weeks early, do not wait it out.
One habit that makes more difference than any of this: a quick rinse before getting in. Body oils, lotion, deodorant and detergent residue from swimsuits are the largest single contributor to dissolved solids in a residential tub, and almost all of it is avoidable.
Frequently Asked Questions
How often should I drain my hot tub?
The common guideline is every three to four months, but it is a starting point rather than a rule. Water life depends on how many people use the tub, how often, and how well the sanitiser is keeping up. A lightly used tub with effective sanitation can go longer. A heavily used one may need it sooner.
What are the signs hot tub water needs changing?
Water that will not hold a sanitiser reading no matter how much you add, foaming that keeps coming back after treatment, a dull or cloudy look that filtration does not clear, and a flat chemical smell. Any of those means dissolved solids have built up past the point where chemistry can fix it.
Can I dump hot tub water on my lawn?
In most BC municipalities, yes, once the sanitiser has dissipated. Stop adding sanitiser several days before you drain, let the level fall to near zero, then spread the discharge rather than concentrating it in one spot. Check your local bylaw, because rules on discharge to storm drains vary.