Havenmade Inc.

Installing A Portable Spa

Many people want their hot tub down in the ground, sort of like a natural hot spring.

There are several problems with the old standard way of installing spas in the ground. That is why I do not recommend it.
The old way is to dig a hole in the ground,  place the plumbed shell (with a layer of foam) directly in the hole, and back-fill it with sand.

The problems with it are lack of energy efficiency, and extremely difficult plumbing repairs. The spa tends to float out of the ground after a few years. This style of spa is usually a custom made hot tub, and is much more expensive per feature than a factory made portable spa. Basically, a badly designed ( as most are)  in-ground spa is just an expensive to own, and very difficult to repair idea.

Because of the moisture in the ground, eventually the (insulation) foam becomes wet, and is useless for insulation. The heat gets rapidly drawn out of the spa hot tub vessel.

Any plumbing problems require that the spa hot tub,  be extracted from the ground and this is an all day job for two or three people.About $3000-$5000 just to get it out of the ground fix it and put it back in the ground.

The best way, that I know of, is to install the spa hot tub in a well engineered vault. This is simply an underground room that is easy to build. It does require a little extra digging and some basic concrete, plumbing, and masonry skills.

You have to plan for drainage inside the vault, similar to the drainage system used in basements.

The procedure goes like this:

1/ Dig out a vaulted room in the ground, make it at least six inches deeper than the height required for the hot tub, (this is for the thickness of the concrete floor), and at least 48 inches bigger than the sides of the hot tub. If you have a 91 inches by 91 inches by 38 inches high spa,the hole would be 139 inches by 139 inches by 44 inches deep, figuring on a six inch acrylic rise out of the ground with a six inch concrete floor.  The thickness of the concrete or block on the wall needs to be added to finish at 24 inches all the way around. There are variations on this, so consult us or a local engineer for any problems with space.   If you get a lot of rain, you may need to have a rock base under the concrete for drainage under the tub (a "French drain").

2/ Dig out and install the drainage system, either attach it to the house sewer system (if above the sewer level), or create a drainage system similar to the leaching field used in septic systems. You may need to put in a plastic drainage bucket in one corner and a submersible pump to catch the water and pump it out ( easiest to do).  You will need some expert help designing it. Call your building department. Different soils require different length of piping and different sizes of pipe and different leach field requirements. The point is to never allow water to build up inside the vault. Put the plumbing for the drain in the corner of the vault.   I recommend that the center be perfectly flat where the hot tub sits, and the perimeter 24 inches be sloped into the drain.  The drain can be a plastic 10-20 gallon bucket with an automatic sump pump (the simplest and easiest to do).  If you have a French drain system then you need a regular basement plastic sump area with holes in the sides for the French Drain pipes to enter the water caught under the spa.

3/ Dig out for the electrical to be installed, either under the hot tub or just outside the spa perimeter. Install the conduit, just above the level of the floor about 6 inches. All conduit must be water proof for underground service.

4/ Place a retaining wall made from concrete reinforced blocks (cinder blocks). Use rebar inside the blocks tied to the floor. Because the blocks are 8 inches thick, the room now is 139 inches square. This is 48 inches bigger than the outside of the spa. This allows 24 inches all around the hot tub for access to the equipment and plumbing.  This is the best for working on the hot tub and or moving the spa in and out without a crane.  It can be ramped into the hole.  If the hole is too small, you will still have to raise the spa for any service to the sides with space limitations.

5/ Using the retaining wall as a concrete form, mark the exact depth of the floor concrete on the wall all the way around the room. Use a laser level or a transit or a hose level to get it perfect. The floor must be level in the center, 91 inches square for a Fallsburg or Timberlake, or Fallriver, as an example.

6/ Place the drain in position about 2 inches below the level of the hot tub's level floor.

7/ Install a string layout the exact size of the spa at the exact level of the floor, using the concrete wall with anchors to hold the string.  Make the spa platform flat and level.

8/ Pour the concrete starting in the center making the area of the spa perfectly level, and the area outside the hot tub run into the drain, with a 1/4 inch per foot run-off. (If necessary make two forms and pour in two concrete sections. One form for the spa area in the center, and another for the drain area.

9/ After the concrete is cured, place the hot tub  in the vault and have your electricity hooked up. A crane or boom truck works well for lowering the hot tub  in place if the space does not allow.

10/ Now build a removable ground level floor decking out of pressure treated and redwood or composite deck boards. (I have a CAD drawing available for you.) If you want a planted area around the hot tub's  top, you use a 6 inch planters with a plastic liner and place it on a six inch lower decking. Make sure the decking can support the dirt. You can be creative with this. It is very important to make it so the planters can be lifted out without harming the plants.
Make an easily accessible door for access to the equipment side of the hot tub. (My drawing makes all sides easy access.)
11/  If the spa is a high performance model, such as (any of our Haven Spas) the Vista, SE or Paramount, or SC you need to have air ducted into the space.  If there is decking as in the photo, just the 1/4 inch spaces between the deck board is enough air.

By installing your spa this way, you will have a very efficient and much easier to live with spa. If the spa ever has a problem it can be repaired with ease, (lift out a few boards and full access) and without the tremendous effort of the old style.  The spa will have more efficiency than an above the ground spa. The vault creates another level of insulation, and keeps water off the spas insulation. This is the best value for  in-ground hot tub installation I know of. The cover is also much easier to deal with.

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Havenmade Inc.

Next month; "Why water flow controls are a bad idea"

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