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Spa pools

We explain the pitfalls to be aware of, key things to know, and cut through the hype so you don’t spend more than necessary.

Note: this report does not contain test results or brand recommendations – it is a general buying guide only.


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Size and price

Spa pools are available in a huge range of sizes and shapes, from 2-person models that fit in a corner to 10-person monsters. There are even extra-long spa pools with a section to swim against a current.

Most models hold 4 or more people. Look closely at the number and arrangement of seats – sometimes it’s a squeeze to fit in the claimed number of people, and there is normally a lot less room for legs than there is for bottoms.

The price range for spa pools is just as diverse, with basic models costing around $4000 through to deluxe models complete with all sorts of features – costing upwards of $40,000.

Price usually has more to do with the number and type of features than with size.

Don’t forget to include the cost of a building consent and fencing (see below) when working out your budget. You should also check whether delivery and set-up are included in the price. If your house has particularly difficult access, getting the spa into position may require a specialist moving company, a crane, or even a helicopter.

Extra features

Even if you know roughly what size spa pool you want, you’ll be dazzled by the array of extra features on offer. These include the number and type of water jets, multi-coloured LED lights, fountains, drinks coolers, sound systems and, yes, pop-up TVs.

While some jets give a much better massage effect than others, you should think carefully about these extras and their additional cost. The best thing to do is “try before you buy”. All good spa retailers should have demonstration pools, so take your togs and a towel with you and try out the models you’re interested in.

Keep in mind that having a spa is often a social event, and the pump and jets on a spa can make enough noise to make conversation difficult. Although there will be times when a long hot soak and a good massage are exactly what you need, often you’re likely to end up sitting in the spa talking without the pump and jets running.

Safety and set-up

Most spa pools are portable, self-contained above-ground units, which are filled from a hose pipe and just need plugging or wiring into a power supply. Models designed to be built in to a deck are basically above-ground models without the side cladding. Most above-ground models can also be built-in.


You’ll need a building consent to put in a spa pool, and a requirement of the consent will be suitable fencing. Exact specifications vary by local authority, but generally the fence will need to be at least 1.2m high, not have any features that would allow a child to climb it, and have self-closing and latching gates.

There may be changes to the legislation that relates to spa pool fencing soon to allow lockable covers to be used. In the meantime, check with your local authority for full details on fencing requirements.


If you’re thinking of putting a spa pool on an existing deck it’s unlikely your deck has been designed to take the extra weight.

A spa capable of holding 4 or 5 people may only weigh 300-400kg when it is empty, but when full of water and people it can easily exceed 2 tonnes – 1000 litres of water weighs a tonne.

Whether you’re building a deck for a spa pool or looking at using an existing deck, you’ll need to consult an engineer to ensure the deck is strong enough. Where possible it’s cheaper and easier to cut a hole in the deck and sit the spa pool on the ground underneath.


Spa pools with small pumps (usually the smaller models or ones with few jets) can often just be plugged into a standard 10-Amp household socket. Look for models that are rated at less than 2400W with pump and heater running. Beyond this you will need to get an electrician to wire in your spa pool. The cost will depend on what’s required to add the spa pool to your existing wiring and fuse box.


Spa pools can be made of fibreglass, acrylic with fibreglass reinforcing, or polyethylene – each has its pros and cons.

  • Acrylic tends to be the most expensive but is also the easiest to care for and the most durable.
  • Fibreglass is often cheaper than acrylic, but needs more looking after and is likely to have a shorter lifespan.
  • Polyethylene is a type of plastic commonly used to make water tanks and sit-on-top kayaks. Although a tough and hard-wearing material, polyethylene has a softer matt surface rather than the more traditional hard shiny surface of acrylic or fibreglass. Polyethylene construction is common at the cheaper end of the spa pool market, but we don’t think that means it’s an inferior material.

Keep in the heat

The most common method of insulation is for the spa’s case to be filled with insulating foam (except for the area where the pump and control systems are located). Models that only have a layer of insulation underneath the shell are cheaper but the heating costs are likely to be much higher than a better insulated model.

The third insulation type is a compromise between the first two, with the base and outer cladding of the spa being insulated. This is cheaper and gives better insulation than just a layer underneath the fibreglass, as the heat from the pump and pipework is retained.

Spa pools also lose plenty of heat through the lid. The biggest factors are the thickness of the insulating foam in the lid and how well the lid seals against the top of the spa. Any gaps are places where heat can escape. See Spa lids (below) for a way to ensure that the lid on your spa is better sealed.

One factor that often gets overlooked is how hot your spa stays while you’re using it. The brochure pictures of happy people in a spa in the snow are fine, but in reality spas with smaller heating units will cool down fairly rapidly with the lid open on a cold winter’s day. A bigger heater can overcome this, but will have higher wiring-in and day-to-day running costs.

Water treatment systems

Spas use a combination of filtration and chemical treatment to keep the water clean and healthy. Filtration systems are all similar – the differences lie in the chemicals.

Traditional systems use chlorine or bromine as the sanitising agent, and these need to be added regularly to keep the active chemicals at the desired levels. Other systems rely on a small amount of salt being added to the water when the spa is first filled. The salt is broken down by a small electric current to give free chlorine ions, which eventually re-form salt.

Salt water systems have some advantages, including:

  • using much fewer chemicals compared with chlorine or bromine systems
  • breaking down some of the chemical by-products in spa water that cause skin and eye irritation
  • less reliance on someone remembering to add chemicals on a regular basis.

In both systems the chemical balance (pH, total alkalinity, calcium hardness etc) of the water needs to be carefully monitored and adjusted for the water to stay at its best.

As well as the primary chemical sanitation systems, many pool manufacturers offer additional systems to help keep the water clean. The most common are cartridges that release small amounts of silver into the water as it is circulated and systems that bubble ozone gas through the spa water.

How often you need to change the water in your spa is directly related to:

  • how often you use it
  • how well you keep the water chemically balanced and clean
  • how often you remember to hose the filter clean.

Realistically you’re likely to change the water every 1 to 4 months.

Ongoing costs

Spa pools aren’t cheap and you also need to factor in the ongoing costs.


  • First you need to heat up the water. Every 500 litres of water in your spa is going to cost around $4 to heat from cold to 38˚C. Although that’s not expensive you will have to refill your spa multiple times a year so it will add to the total running costs.
  • Next you have to keep the water hot. How well the spa is insulated will have an effect.
  • A final consideration is how the spa keeps the water clean and hot when not in use. Some do this by running the main pump periodically, say, for 5 minutes every hour. Others have a much smaller circulation pump that runs constantly. Running the main pump is noisy and can use more electricity than a small circulation pump, which make little or no noise.

All up, your weekly electricity costs for running the spa could be around $25 if you had 3-5 short spas a week.


You’ll need to buy chlorine or another sanitiser, a range of other chemicals to keep the water balanced, and test strips. Less frequently you’ll need silver ion cartridges (if your pool uses them) and replacement filters. You should budget at least $200-$400 a year for these products.

A good tip is to shop around for these consumables when you need them. Your spa manufacturer may try to convince you to use its branded products, but spa-specific generic products from pool shops are likely to be significantly cheaper.

Replacement parts

Longer term you will need to replace the lid on the spa, any soft headrests or other accessories attached to the pool, and maybe even some components of the plumbing.

Remember the Consumer Guarantees Act (CGA) often covers you for more and for longer than the manufacturer’s warranty. If something goes wrong with your spa and it’s out of warranty, use your rights under the CGA.

Spa lids

Most spa pool lids are made from an outer case of vinyl or similar hard wearing material with slabs of expanded polystyrene inside. Polystyrene is a good insulator, but it slowly absorbs moisture over time. This process is accelerated by the hot, moist conditions inside the spa pool. After 3-5 years you may find the lid gets too heavy to lift, or the extra weight causes the slab of foam to break inside the lid cover.

Most outer cases have drain holes in the underside to let out any rain water that gets in through stitching. Unfortunately these drain holes let water vapour get into the polystyrene too. Replacing either the foam core or vinyl outer of your spa lid isn’t cheap.

The cheapest and easiest way to minimise waterlogging of your lid is to get a cheap single-layer vinyl cover made that fits over the top of your spa and goes underneath the insulating lid. This cover stops any water vapour from getting to the lid. The sealing effect also helps reduce heat loss through the lid of the spa. You need to be careful of rain water pooling on top of this cover, but for most people dealing with pooled rain water is less painful than the cost of replacing the polystyrene core of the lid every few years.

Report by Andrew Smith.

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