The Complete Hot Tub Buyers Guide - PART 1

Views 15 Likes Comments Comment
Like if this guide is helpful

Hot Tub, Spa, Jacuzzi or Whirlpool?

Today there is no real difference between a Spa, Hot Tub, Jacuzzi or Whirlpool although Hot Tub is the more common name in the UK. The Jacuzzi is so-called because the first water jet used for hydrotherapy was invented by the Jacuzzi brothers, just like a vacuum cleaner being called a Hoover.

In the 60 s and 70 s, a Hot Tub was an oak or cedar barrel, refillable with water, fitted with a heat source. Today; Hot Tub, Spa, Jacuzzi or Whirlpool are general terms for any outdoor heated hydrotherapy pool.

The latest design is a Swim Spa - a very large hot tub where you can exercise, swim on the spot, or have a spa. This has none of the installation, heating and cleaning costs associated with a normal swimming pool.

Acrylic Shell Colour and Texture

There are three main types of acrylic textures: Pearlescent, Marble and Granite

Pearlescent - Amazing looks, shiny metallic colours, or combinations of these in a swirling pattern. Generally features combinations of Blacks, Silvers, and Blues.
For: Stunning looks, metallic surfaces, looks great with chrome jets.
Against: High maintenance - shows dirt and marks more easily.

Marble - The same as pearlescent, yet with more regular colours such as Greens and Blues which can be more suitable colours for a pool of any kind.
For: Nice swirling blues and greens normally associated with water
Against: High maintenance - shows dirt and marks more easily.

Granite - (often referred to as Quarite) is made from small plastic chips ground up and formed into a sheet with a clear resin.
For: Texture reduces slipping, huge colour choice, lower maintenance, marks are less visible, harder wearing, closer match to natural material such as stone, granite or render.
Against: Lacks the wow factor of the other finishes

Ultimately you should consider how much wear and tear your spa will suffer, how much maintenance you are prepared to do, how important the looks of the spa are, and what materials you will have around the spa.

Make sure you choose a brand of spa using a reputable brand of Acrylic, namely: Aristech or Lucite.

Chinese factories are starting to copy these brands, however Chinese sheets are floated, not extruded and are very brittle, causing huge cracks and splits in spas less than a year old. If the spa isn’t made from a branded acrylic, avoid at all costs as the acrylic is what keeps the spa watertight for ten or so years.

A Lucite or Aristech Acrylic shell backed with several layers of fibreglass is the most expensive spa shell construction method and normally given a 10 yr warranty. Lucite and Aristech are the two largest manufacturers of Acrylic world wide. Other cheaper shell types are Liner, Inflatable, and Roto-mould.

Cabinet Construction

There are two methods of bonding the shell to the cabinet: a shell which sits on the cabinet’s rim or a shell which overlaps the cabinet.

The first method is not very suitable for the UK weather. Water rests on the wooden plinth around the top of the cabinet causing unsightly water marks, eventually rotting and splitting.

The second method, an overlap or lip-over-edge shell, is more expensive to build but allows the water to fall away from the cabinet for years of worry free maintenance.

The cabinet can also be made from various materials. Softwood is generally the most popular, with several varieties used: pine, spruce and redwood. These softwoods are generally unsuitable for the UK due to damp and rotting problems.

Cedar is a soft wood, yet has natural anti-rot and anti-pest properties (even untreated), and is often used in construction as a cladding material. Mahogany is a hard wood - both are far more suitable for our weather conditions.

Synthetic wood (plastic) cabinets are being introduced to the spa market due to low maintenance requirements. As long as the cabinet looks convincing and is UV stable, these cabinets can offer the same visual appeal, insulation, anti-rot and pest resistance as cedar or mahogany, but will never need sanding or treating.

The better synthetic cabinets are literally indistinguishable from cedar, the worst are foil-wrapped fibre board, that will not last. If you are considering a synthetic cabinet, make sure you see a sample and check the guarantee.

Insulation Techniques

Perimeter insulation creates an insulated wall around the spa cabinet and locks the heat inside just like a house. This means that the pumps, heaters, and plumbing are all insulated. Many full foam spas have foam on 3 sides of the spa and nothing on the 4th. So the pumps are cold, the pipes around the equipment are cold, and so is one wall of the spa.

Some brands spray around 10mm of foam onto the spa shell. This insulates the shell slightly, but leaves all the pumps and pipes exposed, so when the heater and pump are activated, the hot water travels through plumbing that could be exposed to temperatures below freezing, defeating the point of the insulation. This also gives a nasty shock when the pumps are activated, pushing the cold water sat in the pipes back through the jets!

Foam can degrade into a brittle, yellow dust over time. Where it is sprayed as a 10mm layer onto the back of a shell, as the shell heats and cools, it expands and contracts meaning pieces can crack and fall off. Some factories support their shells by turning the spa upside-down and pumping the whole spa full of foam. This is fine until the foam breaks down and starts to sag, or if there is a leak or other problem.

Full Foam Repair:  

Full Foam Repair:  

Foam on Shell:

Full-foam means the spa must be jacked up and filled to find the leak while the engineer literally digs all of the foam back out until the leak is found. With this process it can take several trips to site to fix a simple leak that could be repaired the same day on another spa.


Some smaller, cheaper spas have no heater at all and feed the water around the outside of the pump, cooling the pump and heating the pool.

This heat recovery (no heater) system is great for maintaining temperature when the spa is not in use, but open the cover, turn on the jets and you will soon see and feel the temperature drop. The same is true of smaller 1.5kw electric heaters that will struggle to keep-up in colder weather.

Heaters specified as 5 or 5.5kw are generally quoted for the US market when running on 110v these systems are often modified rather than designed for the UK market and can prove unreliable, especially the pump motors.

Generally heater sizes for UK spas should be between 2 and 3.5kw. Sometimes you will find a 6kw heater on a large spa or swim spa.

Ozone or Ultra Violet?

An ozone generator generates ozone gas which is dissolved into the spa water. This, like chlorine, bromine and other sanitisers helps to kill bacteria in the spa. Two types of ozone generator are: CD or UV (Capacitor Discharge or Ultra Violet). These generators inject ozone bubbles into the water neutralizing contaminants on contact, helping to keep the water clean and clear, whilst reducing the amount of other sanitizer (Bromine or Chlorine etc) required. The generator’s CD Chip or UV Bulb will generally need replacing every couple of years. Ozone’s drawback is that it can build up under the cover and attack it as well as other plastic parts, causing staining, discolouration, even disintegration.

A new type of sanitiser is a technology which also uses UV. Unlike a UV ozone generator (which creates ozone gas and injects it into the water), the water passes through a clear tube where it is exposed to a specific spectrum of light that kills bacteria. This has many advantages: It will kill bacteria and oxidise the by-products without introducing any chemicals into the water. Unlike Ozone, it will not attack or stain the plastic parts in the spa. This is very different to a UV ozone generator and is far more expensive.

Spa Covers

Reputable dealers in the UK sell their spas with a thermal rigid cover as standard. Floating Bubble or Solar covers used in conjunction with a hard cover can further improve its performance, yet are not suitable for the UK climate when used on their own.

The purchase cost of a hard cover is far less than a year‘s running costs without one!

Our optional extra-strong covers have an extruded T section of aluminium inserted across each side of the centre fold - these help to improve safety if your spa is installed at ground level.

Pumps and Power

This is an area of the market that is prone to ambiguity. Pump performance is generally quoted in HP or Horse Power. However, American HP is measured differently to UK HP. So a 6HP US Pump can equate to around 1.5HP in the UK. This is to do with American / UK voltages (US=110v, UK=240v) so power is calculated differently. BHP is often used to artificially inflate the perceived power of a spa. 2.5Hp is often referred to as 4.8BHP and 3.0HP is often referred to as 5.2BHP.

Avoid spas with lots of small pumps. More pumps = more chance of a problem. Lots of small pumps is a sign that the spa is probably made in China without CE approval.

Older and cheaper spas use a two speed pump. This is so the same pump can filter/heat the water (on the low speed) and power the jets (high speed). These pumps can be less reliable and noisier than single speed pumps due the motor being adapted to work on two speeds.

Circulation pumps are tiny pumps often fitted to more upmarket spas and normally run 24/7. These pumps are just used for heating/filtration, not for powering the jets. Their small motors and 24hr operation, not only saves energy, but reduces chemical consumption by not allowing the water to sit still and stagnate.

Jets and plumbing

The size of the plumbing, bends and other factors affect the pump flow rate. The best test is to put your hand or body in front of the jets, with all of the jets switched on and feel the water pressure coming out.

Make sure that the spa you buy has a matched pump for the number of jets. Too much power and not enough jets will mean that they are uncomfortably powerful (and the pumps will not last as long), whilst too many jets and not enough power means you are not getting proper hydrotherapy.

Diverter valves can help this, but you should always check the spa with the diverter valve in the 50/50 position so that you can see how the spa will perform when every seat is used simultaneously.

Some jets have more than one nozzle. Make sure the brochure is counting the actual water jets and not each nozzle on every jet.

Have something to share, create your own guide... Write a guide
Explore more guides