Note: We have not tested or reviewed any spa pools. We're unable to do this due to the costs involved and difficulty in testing durability over time.
Size and cost of spas
Your main considerations for choosing a spa should be the size, your budget, and what features you’re after.
Sizes range from two-person models up to spas that can fit nine people. That said, it might be a bit of a squeeze to get the stated number of people in – so be sure to check.
We found a basic three-person spa from $5,500 through to a nine-seater with souped-up jets for $36,000.
Be sure to weigh up the features. A LED light-cascading waterfall might look nice, but the number of massage jets might make your pool time more relaxing.
Good spa pool showrooms have demonstration models you can try. So, make a booking, take your togs and towel, and try the models you’re interested in.
What’s a spa made of?
Spa pools are usually made of fibreglass, acrylic with fibreglass backing or polyethylene.
While all these materials are strong, the cost and durability can depend on the thickness of the material used. For example, a spa with 8mm of acrylic will be stronger than a spa with only 3mm.
Most spa pools are portable, self-contained above-ground units. They can be filled with a hose pipe, and just need plugging or wiring into a power supply.
You don’t need a consent for your spa if it sits directly on the ground, and its capacity is no more than 35,000L.
Installing a spa outside is generally straightforward unless your home has difficult access. If so, getting the spa into position may require a specialist moving company, a crane, or even a helicopter.
You need a firm, flat and level base to put your spa on. You also need to think about drainage. The water in a spa needs changing every one to four months, so having it by a water outlet makes life easier.
Because chemical treatments are used to keep spa pool water clean, it needs to go through the sewer system (not a storm drain).
You’ll also want to position the spa so it’s easy to clean and maintain.
Getting a spa inside a house can be tricky. It depends on the layout of your home, but you may have to remove doors, even walls, to get it inside. If you’re building a new home it’s best to think about where you’ll put your spa during the planning stage.
If you want to install a spa on the first floor, or a deck or balcony, talk to an engineer. For example, an empty spa that only weighs 400kg can easily exceed two tonnes when full of water and people.
You need to ensure the structure of the house can support the weight of the spa, water and bathers. You’ll also need a building consent if you’re changing the structure of your home, or if you’re building a deck that’s more than 1.5m high. Check with your council about the requirements.
Spa pools with small pumps (usually smaller models or ones with few jets) can often come ready to be plugged in.
Check with the retailer whether you’ll need an electrician to wire in your spa pool.
The cost depends on what’s required to add the spa pool to your existing wiring and fuse box.
The better insulation your spa has, the cheaper it is to heat.
There are three options for insulation. The first is to have insulation foam sprayed on the spa’s shell. While it’s cheap, it’s generally the least energy efficient.
The second option is to have full foam insulation. While this dramatically cuts heat loss, the extra insulation can make the spa expensive to service.
It may also be a problem if your spa springs a leak. The extra insulation can soak up the water before you discover the leak. This will add to the weight of the spa, which can have serious consequences if your spa is on an elevated deck.
The final option is to have the inside of the spa cabinet insulated. This has the best of both worlds in that it keeps the water and plumbing insulated, while making it easier to access if it needs repaired.
Getting a decent spa cover also helps insulation.
While most covers are made with hard-wearing materials, they will absorb moisture over time and eventually need to be replaced.
To prolong the life of your cover, you could buy a cheap single layer vinyl cover and put it underneath the outer cover (this also reduces heat loss from the spa).
One factor that often gets overlooked is how hot your spa stays while you’re using it. A spa with a small heating unit will cool down fairly rapidly with the lid open on a cold day. A heater with a controller that automatically adjusts the temperature can overcome this, but will have higher wiring and day-to-day running costs.
Spa covers and fencing
Your spa pool must either have a fence around the pool or a cover to prevent children entering unsupervised.
If you’re buying a cover, make sure it meets building regulations, which state it must:
The walls of the spa must be at least 760mm tall to ensure small children can’t climb over.
If you’re building a fence around your spa, you’ll need a building consent from your council. The fence must not have any features that would allow a child to climb it and have self-closing gates.
Spa pools (with a fence) must be inspected every three years to ensure they meet regulations. Your local council or independent qualified pool inspector can carry out the inspection.
You can find a list of qualified inspectors at the Trading Standards website, which is run by the Ministry of Business, Innovation and Employment.
To keep your spa bubbling, there are ongoing costs you’ll have to pay.
Spas require filtration and chemical treatment to keep the water clean.
Filters act like sieves to remove particles from the water. The efficiency of the filter can also depend on the pump. If your spa has a low-flow pump, the water isn’t going through the filter as often, and so isn’t cleaning the water as often.
Traditional water treatment for spas is chlorine or bromine.
Other options include a small amount of salt being added to the water when the spa is first filled. The salt breaks down and produces chlorine ions, which eventually re-form salt.
Hydrogen peroxide sanitisers can also be used for those who want a chlorine alternative.
While other water treatment products may tout they’re chlorine-free, check what’s in them. Also ask for evidence the product is effective at killing bugs in your spa pool.
The levels of water treatment chemicals should be checked before each use, and during weekly maintenance. The chemical balance (pH, total alkalinity, calcium hardness) also needs to be checked weekly. You should also clean the filter at the same time.
All these chemicals and test strips will set you back about $200-$400 a year.
How often you need to change the water in your spa depends on:
Realistically, you’re likely to change the water every one to four months, or more often if the water isn’t clear or it smells. Once empty, the spa will need a good scrub before being refilled.
Every time you replace the water in the spa it’s going to cost between $10-$30 to heat it from cold to 38°C. Keeping the water warm will also cost.
Running the pump to keep the water clean will add to your power bill. Some spas pump automatically, say for five minutes every hour. Others have a much smaller circulation pump that runs constantly. Running the main pump is noisy and can use more power than a small circulation pump, which makes little or no noise.
Some retailers estimate a well-insulated four-person spa costs $1 a day. So, you can expect to add at least $30 to your monthly power bill. If you change the water, your monthly cost could be $60.
Long term you will need to replace the lid on the spa, any soft headrests or other accessories attached to the pool. Even some components of the plumbing may need replacing.
Wood-fired hot tubs
A wood-fired hot tub can be an appealing prospect if you don’t plan on using the spa every day.
Rather than keeping the water in the tub for long periods of time, these tubs are designed to be filled, used for a few days and then drained. This means no chemical treatment is needed.
While the lack of chemicals may make life easier, setting it up takes some work. Like the name suggests, wood-fired spas are heated by firewood, and can take up to five hours to heat (and even longer in the middle of winter).
While you’re saving on electricity and chemicals, you need to consider the cost of firewood and the effort to get it heated.
The same regulations of having a cover or fencing (when it’s full) apply.