Considering a Hot Tub or Hydrotherapy Spa for Your Home? (A Deep Dive Part II)

Shell Construction Must Be Sturdy and of the Highest Quality

What goes into a hot tub shell? To be clear, the shell is the part you sit in. There are two basic kinds of shells. There are inexpensive, vacuum-molded acrylic shells that are formed into the shape of a hot tub, or there are reinforced fiberglass/acrylic shells. The reinforced fiberglass/acrylic shells have textured or shiny surfaces made from acrylic.

Once the shell is made, manufacturers turn it upside down to add reinforcement. Most of them apply special resin to the underside of the shell. The resin forms a barrier against intrusion by vapor and moisture. The resin barrier prevents minerals and salts from penetrating the layers and delaminating the surface, or causing unattractive blistering. Once the resin barrier is in place, chopped fiberglass is sprayed in the shell. And here’s where the game changes.

Beginning at the low end of the market, you’ll find the box-store variety of spas. To keep the price down, once the chopped fiberglass is blown in, they’re done. Stopping at this point sets the hot tub up for serious problems, because the shell won’t be able to hold the weight of the water once it’s filled.

Problematic Work-arounds

Since the manufacturer can’t sell you a hot tub that’s simply going to collapse, they add a metal or wooden frame. That might sound like a reasonable solution until you consider that the weight of a full hot tub on the supports’ contacts creates pressure points, which can fail causing leaks and distortions of the tub.

The better companies apply enough fiberglass under the shell and then press the fiberglass to fill all the gaps and air pockets. This method of manufacturing the hot tub shell results in a self-supporting hull. Few companies do this, however, because the process is intensive in terms of both material and labor and, therefore, more expensive. Of course, the benefit is that when the shell is properly built, the pressure disperses evenly across all the surfaces. There aren’t any pressure points and your hot tub shell will last much longer.

Insulation in a Hot Tub is Vital

Turning to the functioning of the hot tub, we need to talk about the issue of heat loss and maintaining a comfortable temperature. Since air tmperatures and evaporative processes drop the water temperature, the more exposure water has to the air, the more heat loss your hot tub will have. Insulation is the key. The type of insulation used for hot tubs is foam. Simply put, the greater the amount of foam, the better the insulation—and the more money you will save on energy to heat your water.

Fully foamed hot tubs leak less than partially insulated tubs, showing the importance of quality workmanship in the product you purchase. In addition, the jets in the tub should be glued and clamped to the water pipe. Once water is flowing through the plumbing, the pressure and weight increase. As you turn the water and jets on and off, you pressurize and depressurize all the connections. Each joint becomes a stress point. When the tub is fully foamed, each stress point has extra support.

Old Days Had Old Ways

In days past, well-insulated hot tubs used polyurethane foam. There was a problem with this method, however. Over time polyurethane foam hardens. Once that occurs, if you ever need to service your tub, access is a big problem. To repair a leak or make any kind of repair, you have to break through the now hardened insulation. You’ll need a heavy-duty saw or a hammer and chisel.

How did manufacturers handle this problem? They avoided using polyurethane foam, and instead placed insulation around the perimeter of the cabinet and away from the shell. Unfortunately, this type of insulation is highly inefficient. Back in those days, energy costs were low and people weren’t particularly concerned about conservation of resources, so little importance was placed on the issue of heat loss. You either kept your tub hot all the time or, whenever you wanted to use it, you fired up the heater, warmed up the water and got in.

Other questionable insulation solutions exist. Some companies use a thin layer of bubble wrap stuffed inside the skirt. Other makers blow a few inches of expanding foam inside the skirt area. There are a number of problems with these methods.

First, there is little heat retention, which defeats the purpose of having insulation in the first place. Another problem is that this sort of random stuffing of insulation covers the motors that run the hot tub. Unlike the water, which you want to remain hot, engines need to be cooled to prevent burn out.

Once the bearings in the motor wear out, you are going to have more and more expensive problems. And once the motor stops working correctly, there’s a likelihood that it will simply go into disuse—which is not the way to get the most out of your investment.

Technology Improvements and Breakthroughs

Insulation technology has advanced significantly in recent years. The new foam being used today never hardens. It’s environmentally safe and has a host of other advantages. Filling the cavity is now simple, because you can inject as much as ten times more insulation, realizing much better heat retention. If you need access to service the shell or equipment, it’s a cinch. You simply cut out the soft foam out of your way. Once you’re done with the repairs, refill the gap with new foam.

You might ask, why not place the motor and heater outside the shell? There’s a benefit to having them inside. If you’re running pipes on the outside of the tub, they will be exposed to cold air. Now the water you’re heating is being cooled on its way to your hot tub. That journey will require much more heat than if your unit is self-contained. If you go through a really frigid period, your pipes could freeze up. Water expands when it freezes, and its expansion could severely damage your pipes and equipment.

Harvesting Heat to Save Money

What about using the motor heat, you may ask? When done correctly, the motor heat can be harvested to raise the temperature of the water. During the cool seasons, the proper reclamation of motor heat helps raise the temperature of the water and lower the burden on the heater and your energy costs. Of course when it’s hot in the summertime, the water in your hot tub will likely stay quite hot just from the transference of motor heat.

Here’s how it works: underneath the seating area in the cavity where the insulation is applied, there are hollows created by the shape of the seats. In these hollows, the insulation can be reduced without diminishing the heat retention. The hollows become the ideal place to set the motors, because there is airflow around them for cooling. Intakes can be placed to recycle the heat to the water.

Winter Care

Freeze damage is not covered under warranty. When we place the motors inside the shell, we can preserve the motor heat. The motor is also kept safe from outside elements, and is protected from freezing. Even in the event of a power outage or ice storm, the well-insulated hot tub will preserve the warmth like a thermos. Even if the power is out for a few days, in all likelihood you won’t have to be concerned about damage from a freeze.

If you ever plan to shut your spa off for an extended period of time during the winter, contact you service company first. It’s not enough to empty the tub. You have to have all the plumbing blown out because if there is water in the pipes, plumbing, filters, or pumps it will expand when it freezes and cause extensive damage.

Hot Tub Installation: Get It Right the First Time

If you’re placing your hot tub on a deck, the deck needs to be strong enough to support the weight of a full tub. If you’re planning to situate your hot tub on the ground, don’t be taken in by the pitch that a fiberglass shell can just be set on the grass. The ground needs to be prepared.

It’s not that the hot tub will be damaged when it’s placed on the ground. Preparation is necessary so that the ground settles evenly. If you don’t prep, the ground will settle out of level.

Make sure that whatever type of hot tub you’re buying, you don’t just drop it on the grass and skip ground preparation. Always have a proper base placed under your hot tub. Doing so will ensure a longer life for your tub and more time to enjoy all its benefits.

Buying a personal spa is one of the nicest things you can do for your health and well being. It’s a gift that will give you a lifetime of pleasure. Contact us at B&B Pool and Spa Center, we’ll be happy to answer your questions about what’s involved with spa ownership.