Swim spas are larger, cooler, and used differently from hot tubs. Here is how the shock routine changes, including the algae issue most owners hit.
Swim spas are typically 3,000 to 6,000 litres, run at 28 to 32C in summer, and get used for short bursts of activity rather than long soaks. The shock routine that works for a 1,200-litre hot tub at 38C does not transfer directly. Here is how to adapt it.
Most non-chlorine shock products quote a dose per 1,000 litres. A 4,000-litre swim spa needs four times the dose a 1,000-litre hot tub needs. Owners often underdose because they were used to the small amount that worked in their old hot tub.
Buy shock in bigger pots for a swim spa. The economy of a 5kg tub over fortnightly small bottles is significant.
Below 30C, algae can grow if free chlorine drops. A swim spa run at 28C in summer is vulnerable in a way a hot tub at 38C is not.
Keep free chlorine at the upper end of the band (4 to 5 ppm). Add a small dose of polyquat algaecide at every refill as a preventative.
Shock weekly with chlorine, not just non-chlorine. The chlorine residual the next day is a useful algae deterrent.
Swim spa filters are larger and clog faster. Rinse weekly, soak monthly.
The cover is bigger and prone to sagging over the long water surface. A central support bar (a pool noodle works) under the cover stops it pooling rainwater.
When shocking, run the jets and the swim system together to circulate the entire volume. Just running the seat jets leaves the swim end uncirculated and undosed.
Bromine works less well at swim-spa temperatures because the lower temperature reduces its activation rate. Most swim spa owners use chlorine instead.
Yes, and it is a popular choice because the lower set temperature suits the cell longevity. Size the cell for the larger water volume.