Rotationally Molded Hot Tubs

Rotationally molded hot tubs, also referred to as roto-molded hot tubs, emerged and have been one of the best options for decent hydrotherapy at an affordable price for the past 15 years.  These tubs are not as lightweight as inflatables or soft sided hot tubs,however, they are more durable and arguably a better value for the money .  They typically weigh between 200-300 pounds making them very portable and have ergonomic (contoured) seating for maximum comfort.  They also feature better hydro-massage therapy because they  have more water jets than inflatables or soft sided tubs.   These units typically run on 110v/15amp electrical making them a convenient plug and play option, however, they can also be converted to 220v (30-50 amp) for better performance (220v allows heater and motor to run at the same time).  For the most part, roto-molded hot tubs range in price from $2000-$4000 but there are a few brands with unique features that go up to $6000.

Roto-molding is a manufacturing process that takes a hollow cast mold filled with powdered plastic resin (high density polyethylene) that is heated up and rotated slowly on two axis points.  The mold is heated externally causing the powder to liquefy and spread evenly throughout the inside of the cast mold as it is rotated.  The mold is then allowed to cool and the rotating continues to ensure even thickness throughout entire shell of the hot tub.  Once the cooling and rotation cycle is complete then the hardened hot tub shell is removed from the mold.  It is important to note that shell comes out in one single piece (unibody) which makes it extremely durable.

Below is a simple pros and cons list for this type of hot tub when compared to a traditional hot tub;

Advantages:

  1. Inexpensive – Prices range from $2000-4000.  It is important to note that the higher end of the price range starts to overlap with the starting price range of a traditional hot tub which can offer more therapeutic benefits.
  2. Extremely Portable – the lightweight design allows it to be easily moved within the backyard or transported to a different location. The units are not as lightweight as an inflatable or soft sided hot tubs, however, in most cases the hot tub is between 200-300 lbs.
  3. Convenient 110v Plug and Play – these units conveniently plug into a standard 110v outlet and draw under 15 amps which means no special electrical work would be required. Furthermore, some manufacturers offer a heat recovery design which allows the hot tub to heat while the motor is running because it recovers the heat from the motor and transfers it into the spa to keep it warm. A traditional 110v with a separate heater has a limitation whereby when the heater is on then the jet pump must be off and vice versa.  This hurts performance because when you sit in the spa and turn the motor on then the heater shuts off causing the hot tub to cool.  It is important to note that most roto-molded hot tubs on the market can be run on 110v or 220v electrical.  This added flexibility is ideal if you want to run a dedicated 220v line at a later date for improved performance.
  4. More Durable – Roto-molded hot tubs are more durable compared to traditional hot tubs in a sense that they don’t have any wood in them to rot and are made of a single piece (unibody) shell design which makes them very strong. The single piece shell also give them a mostly sealed design which keeps unwanted pests out and heat in.

Disadvantages:

  1. Less Attractive – Roto-molded hot tubs are less aesthetically appealing compared to traditional hot tubs because they have a more plastic look to them. Traditional spas come in many more colors, shapes, sizes, and offer more entertainment/aesthetic options.
  2. Less Performance – Although roto-molded hot tubs have better hydro-massage therapy than inflatable or soft sided tubs they are still inferior to traditional hot tubs. Roto-molded hot tubs generally offer between 10-30 small water jets due to the limited space available for plumbing and also because they run on a smaller 1.5-3 horsepower jet pump.  A 1.5 continuous horsepower pump or a 3 brake horsepower pump is all that can be run on a 110v/15 amp service.   Another performance limitation is the heating of the spa as it can take between 1-2 days to fully heat a rotationally molded hot tub (110v).  The small heater usually warms up the water between 1-2 degrees per hour and depending on the time of the year it can take 40 hours to get up to 104 degrees with the cover on.  These units also have tendency to lose temperature quickly when the cover is off and the hot tub is in use because in most cases the heater and motor cannot run simultaneously on a 110v/15 amp circuit.   It is important to note that most roto-molded hot tubs can run 110v or 220v so an upgrade in electrical service can be done at a later date by the home owner to improve the aforementioned performance issues.
  3. Less Efficient – Although roto molded spas are arguably the most efficient 110v hot tubs on the market they are still less efficient than a traditional hot tubs running on 220v.