WOODEN HOT TUBS
QUESTIONS AND ANSWERS

Most Frequently Asked Questions

Although acrylic spas are by far more prevalent today than wooden hot tubs, it was the wooden hot tub that began the experience of social bathing in America. Whether to purchase an acrylic spa or a wooden hot tub depends mostly on personal preference and each individual situation. There are however many reasons for choosing a wooden tub over a plastic spa.

Because they are assembled on site, a wooden hot tub can be carried through any doorway, down any stairs or through any other narrow access. With a spa, you have a large one-piece vessel which can be unwieldy or impossible to move into its final location.

The vertical walls and greater depth of the wooden tub surround the bather with more water than would be found in a spa, so there is a greater effect of buoyancy in the hot tub. In addition, there is typically much more leg room since you can stretch out under the bench, and taller bathers are more comfortably accommodated.

The overall size of the hot tub, depth and diameter, can be customized to fit anything you can imagine. The exact height of the bench, and the location that the jets are installed are exactly as you like.

Because of a wooden hot tub's greater depth, a smaller diameter hot tub will seat the same number of people as a larger plastic spa. For example, a 5' round hot tub will seat as many people as a 7' square spa. And a smaller surface area means less heating expense.

And, of course, there's the rustic look of a traditional wooden hot tub. From an aesthetic point of view, nothing matches the appearance of a wooden tub.

Thickness of wood :
Roberts Hot Tubs' western red cedar and Alaskan yellow cedar hot tubs have a finished thickness of 1-3/4". While all hot tubs are constructed of what's commonly called 2x6, other hot tubs frequently have a finished thickness up to 1/2" thinner. Thicker wood provides more stability, less warpage, more insulating value, and a longer life.

Round vs. flat bands :
Roberts Hot Tubs use bands made of 1/2" cold rolled circular steel with a tinsel strength of 10,000 pounds. The bands are polyethylene coated and held together with solid steel lugs and stainless steel nuts to eliminate corrosion. Flat bands, though quite attractive, greatly shorten the life of a hot tub. Water accumulating under a flat band can cause pockets of dry rot in as little as five years. ( view comparative )

Bench design :
The unique bench design of Roberts Hot Tubs is completely supported from the side of the hot tub. Because the bench has no legs you can stretch out in comfort without the possibility of stubbing your toes or entangling your feet. The bench can be installed at the height of your choosing, or split into multiple heights to accommodate different people.

Quality of equipment (pool equipment rather than underpowered "wimpy" spa pack).

Thicker more insulating cover :
Roberts Hot Tubs was the first to design and implement the use of a 6" thick tapered insulating cover with an insulating seal along the entire hinge. These covers, that come with every complete hot tub system, have an insulation value of R-21 and provide up to 60% more insulation value than the "normal" spa cover.

Ease of assembly due to precession of manufacturing process :
The computer aided milling process of Roberts Hot Tubs means the tubs are a snap to assemble. Proprietary manufacturing equipment produces tolerances of less than 3/1000 of an inch. This guarantees there's no need to alter the final stave, and no "package" of various sized staves to pick from to finish assembling the hot tub. Hot tub bottoms are even computer stamped to show the exact placement of each stave (vertical board).

Tongue & groove staves vs. ball & socket or flat sided :
Roberts Hot Tubs uses a tongue and groove on the edge of the staves. Although this is more work due to different diameter tubs requiring different angles on the sides of the staves, it allows for more surface contact, a smoother finish, easier assembly as the staves are self aligning and no chance of splintering due to thin edges.

6" x 4" chine joists :
Roberts Hot Tubs sit upon 4x6 chine joists. Although 4x4's would work (and save a bit of money), the bottom edge of the tub would be so close to the ground that debris would be able to collect and prematurely promote dry rot. 4x6's lift the tub high enough to allow for optimum air circulation. This additional height also allows for a drain fitting to be installed in the floor so that when the tub is drained all the water drains out. The bottoms of Roberts Hot Tubs are also thick enough so that only 3 chine joists are required (up to 6' diameter tubs) for proper support. This makes installing the hot tub simpler since it's easier to level the 3 chine joists as compared to 4 or 5.

Whirlpool water therapy is both physical and mental. A number of muscle-skeletal aliments and injuries are treated with whirlpool therapy, from arthritis to sports injuries.

A hot tub improves circulation, and a properly designed and operating system will have jets powerful enough to have a massaging effect for the "garden variety sore muscles" from which we all suffer from time to time.

Those sore muscles often come from the stress of daily life, and therein lies the added effect of hot water bathing. As you relax in a hot tub, you're working on the root cause of your problem - stress.

Unlike the limitations of plastic spas, in a wooden hot tub jets can be placed virtually anywhere you like, whether it be high on the side for massaging your neck, low for your lower back, or even on the floor for massaging your aching feet.

Unlike cold water storage tanks, there are much more stringent requirements for the grade and type of wood that should be used to make a wooden hot tub. There are many aspects in the qualities of different species of wood. Each of these aspects has an importance in how it relates to the quality of a wooden hot tub and it's life expectancy. The higher wood qualities are referred to as "clear, heart, vertical grain", however, there's more to it than that when it comes to wooden hot tubs, or, high quality wooden hot tubs.

Natural resistance to decay is the top concern when choosing a species of wood to use for a hot tub. Different cuts from the same wood species, or even the same tree, can have vastly different rot resistance qualities. The ability of the wood to properly swell is important for the hot tub to maintain water tightness. The "cut" or grain pattern of the wood is also important, to eliminate any possibility of warping, pealing, delaminating or splintering.

Resistance to decay :
The wood used in a hot tub must have a natural resistance to decay and maintain that resistance in warm water. Woods that work well for hot tubs include a variety of cedars, teak, jarrah, cypress and old growth redwood.

A wood's decay resistance comes over time and is typically stronger the slower a tree grows. The number of growth rings per inch is a good way to judge how fast a tree has grown. More growth rings per inch indicates a slower growing tree and typically means more resistance to decay. Soft woods used in hot tub should have a minimum of 6 to 8 growth rings per inch, with 20 to 50 being much more ideal. Various parts of a tree also have different resistance to decay. The outer part of a tree, generally lighter in color, is called sap wood and is the newest growth. It has not had the necessary time to develop the natural decay resistance and under no circumstances should it be used in a hot tub. Only the heartwood from the center of the tree possesses the natural decay resistant properties necessary for a traditional wooden hot tub.

Knots are also something to be completely avoided. Besides the fact that knots can be uncomfortable to sit on or lean against, they are also prone to leaking. Additionally the outer most part of a knot is sap wood, and prone to premature decay.

Vertical vs. Flat Grain :

Flat Grain-
Lumber that is sawn approximately parallel to the annual growth rings so that some or all of the rings form an angle of less than 45% with surface of the board. Flat grain wood expands in thickness, rather than width. Width expansion is what seals a wooden hot tub.

Vertical Grain (quartersawn or VG)-
Lumber that is sawn at approximately right angles to the annual growth rings so that the rings form an angle of 45% or more with the surface of the board. Vertical grain boards are more stable, will not peal or splinter, and are less likely to warp or shrink than flat grain boards.

As one of our European distributors says, "vertical grain western red cedar is a vastly superior to flat grain and will last for many more years. The flat grain stuff is susceptible to wear and tear, tends to become rough and looks terrible after just a short time."

The wood used in a wooden hot tub must also have a pleasant appearance. Despite the high cost and limited availability, clear heart, vertical grain Western Red Cedar fulfills all of these requirements better than most any other wood (teak, jarrah and a variety of other cedars are also excellent woods for hot tubs).

Absolutely! While other manufacturers finished thickness is as thin as 1" - 1-1/4", our wooden cedar hot tubs are a full 1-3/4" thick. The extra thickness adds a much greater insulation value and over time there is much less proneness to warping and more importantly, dry rot. The thicker the wood, the longer the life span of the wooden hot tub.

The tables below show approximately how much water is held by a variety of sizes of our wooden hot tubs along with their filled weight. Also shown is the average number of average adults that each hot tub will comfortably seat.

Weights above may be over estimated to cover different types of wood offered.

Absolutely not ! This is another common misconception about wood hot tubs. In fact, unlike plastic spas, wooden hot tubs don't crack, chip, blister, bubble, fade or stain. To clean a hot tub all one has do is drain the water and rinse it out. If necessary or desired they can be gently scrubbed with a soft brush and a mild bleach/water solution . Also unlike a spa, wherein 8 to 10 inches of water remains, when you drain a wood hot tub all the water drains out.

Most people leave the outside of a wooden tub natural bare wood. As with any type of wood, over time it will naturally gray from the elements. If you choose to put a finish on the outside of the hot tub, the directions for that finish will need to be followed carefully and most likely reapplied annually. Left unfinished, a wooden hot tub just looks better and better with age (of course this is our own opinion).

The cost of operating a wood hot tub varies widely depending on the size of the tub, the climate, the configuration of the installation, and most importantly, the price of gas or electricity in your area.

While this question is virtually impossible to answer here, what we can tell you is this; Heat rises, with about 80% of heat loss occurring from the top. While a wooden hot tub may hold more water than a spa, due to the fact that a comparable sized wood hot tub has a smaller surface area than a plastic spa, they generally cost about the same to operate as a spa.

Additionally, to further help reduce heating costs, we've developed a 6" to 4" tapered insulating cover with an R value in excess of R-22. This cover is included with all our complete hot tub systems and reduces heat loss from the top of the hot tub an additional 50%, as compared to other "normal" insulating covers.

The rate at which the water heats depends on two things. The size of the hot tub, and the size of the heater. Below is a chart, showing the size of hot tub, size of heater, and how many degrees per hour the hot tub will heat.

This is another common misconceptions about wooden hot tubs. Indeed wooden hot tubs will leak ever so slightly for the first few days after assembly, but the amount of leaked water is generally not even noticed.

After making wooden tubs for nearly three decades, we can say that there are basically only two reasons why a natural wooden hot tub would leak. Without a doubt the most common reason is overuse of chlorine or bromine, which can attack the wood, causing leaks.

This problem can be avoided simply by being diligent enough not to exceed safe levels of halogens in the water or by using an ionizer which will greatly reduce the need for halogen sanitizers.

If a tub holds water perfectly for months or years and then begins leaking inexplicably, this is usually indicative of over-halogenization. And, if the problem is identified early enough, the damage can be halted and repaired with little cost or time.

Much less common than leaks due to halogens are leaks in a hot tub due to improper assembly. This is indicated by a tub that never seems to seal at all. Our assembly instructions offer an easy and detailed description of the proper assembly procedure, so this is only ever a problem for installers that fail to read the assembly instructions.

This is another common misconception with regard to wooden hot tubs. In fact, wooden hot tubs are no less sanitary than acrylic spas. Improperly sanitized, both wooden tubs and acrylic spas can represent a health hazard, but there is no evidence that the natural wood is more likely to harbor organisms as compared to the acrylic. In fact, in a university study of kitchen cutting boards, it was found that while bacteria multiplied and prospered on plastic boards, it died on the wooden ones. A copy of that study can be found here.

The important point to remember is that, regardless of the material from which your wood hot tub or spa is made, proper sanitization is the key.

There are a number of options and accessories that you may wish to consider along with your hot tub system.

Larger Pumps, Extra Jets:

All 5' and larger hot tub systems come with a 1-1/2HP, 240v, 2 speed pump and four massage jets , this is generally adequate. However if you would like more jets, it is a simple matter to add a larger, or additional pump to accomplish this. The smaller oval tubs generally have two jets, one at each end, while the ofuros and soaking tubs usually don't have any jets.

Air Blower System:

The next accessory to consider is a Bubbler System. The bubbler, or air blower. blows bubbles through a small holes in a ring of pipe that is attached beneath the bench. The effect it creates, sometimes called a Champagne effect, can be very soothing. Included with the Bubbler System is a 1-1/2 HP, 240v compressor, additional plumbing and controls.

Larger Gas Heater Option:

The standard gas heater provided with our hot tub systems is a 100k Btu gas heater. Larger heaters can a great option if you want to be completely spontaneous as to when you want to use your tub .(see chart for heat up times)

Covers:

There are two different types of covers that you should put on your hot tub. One is an inexpensive floating blanket that rests right on the water. The other is an insulating cover which fits over the top of the tub. These two covers and the layer of air between them virtually eliminate surface energy losses and will pay for themselves in a short time, even on indoor installations.

The complete hot tub systems come with a UV inhibited marine grade vinyl covered 6" thick foam cover. Some of the available cover options are, a wooden cover, aluminum cover, or our roll cover. Please see the section on covers for descriptions in more information.

Low Voltage Light:

The Low Voltage Light for hot tubs features subdued lighting inside the tub. The light is supplied with a separate spa side switch and a set of five colored lenses to suit your particular mood. The colored lenses can be changed from inside the tub without any need to drain the water.

Installation Questions

Hot tubs are not at all difficult to assemble, at least ours aren't. Our assembly instructions are written with the do-it-yourself installer in mind and take you step by step through the basic hot tub assembly process. No special tools or skills are required.

The computer accuracy we use in manufacturing our wooden hot tubs means that not only is there no need to cut or modify the final stave to fit, but the bottom is also computer stamped to indicate the exact placement of each stave (vertical side board). We can generally assemble a hot tub, on site in under 30 minutes. Figure about 2 hours for the novice, a little less if you have some help.

Include with the complete assembly instructions is a phone number to call for 24 hour, 7 day a week technical assistance regarding installations. We can also ship a hot tub fully assembled, but beware, this adds to the shipping costs and can be rather difficult to move into location on your site.

Besides assembling the wooden hot tub (listed above), the complete system also includes the necessary equipment along with most everything else needed for a basic installation. While many people do hire a contractor to do the complete hot tub installation, a good many do the majority, if not the entire installation themselves.

The three more difficult aspects of installing a wood hot tub are, providing a concrete pad for the hot tub and the equipment, running the gas line to the gas hot tub heater (if so equipped) and running the electrical circuit to the time-clock. Excluding these 3 aspects, installing a complete hot tub system should be just a weekend project for a "home handyman".

All of the hot tub plumbing is accomplished by gluing together PVC piping, and the support equipment is shipped complete with everything necessary to install your system. The instructions included contain complete plumbing diagrams and a simple to follow wiring schematic. We even provide the PVC glue and a special mallet for assembling the hot tub.

A wooden hot tub needs to sit on either a deck engineered and reinforced to carry the weight, or solid concrete. Anything else could allow the hot tub to settle unevenly and possibly cause leaking.

The necessary thickness of a concrete pad may vary depending on different soil conditions. Generally a 3½" thick, wire reinforced pad on stable ground will suffice. Footings may or may not be necessary depending on local conditions (freezing, rain, ground movement etc.). Consultation with a local concrete contractor is advisable.

National building codes call for the equipment to be a minimum of 5' from the hot tub, or separated by a permanent solid barrier so that the distance from the water line, around the barrier, to the equipment is at least 5'. The maximum distance is limited only by your imagination and individual requirements. 20', 30' or even 50' from the hot tub to the equipment is perfectly acceptable.

The only downside to the the equipment being a great distance from the hot tub is that if the system hasn't run for a few hours the water in the pipes will have cooled down. Jumping in the hot tub, then turning on the pump, you'll feel the cool water coming out of the jets. This is easily overcome by turning on the pump a minute or so before entering the hot tub. Additionally, if the equipment is further than 40' from the hot tub, the size of the piping should be increased one size so as to not cause a reduction in jet flow and pressure.

The standard complete hot tub system, which included a gas heater and 2 speed pump, requires a 20 amp 240v circuit including a ground and neutral. If an electric heater is opted for rather than a gas heater, and additional 60 amp circuit is required for the 11kw heater, while a 30 amp circuit is required for the 5.5kw heater. Options such as an additional jet kit, or an air bubbler system require additional power.

Many people design and build a deck around their hot tub. There are a number of things that should be considered and designed into suck a deck. The decking should not run over the top of the tub, but should be flush to the top of the hot tub. On round hot tubs a small gap should be left between the decking and the hot tub. ¼" to ½" is sufficient. The exception to this is oval hot tubs. In oval hot tubs, over time, the pressure of the water will try to round out the top of the hot tub. Slight contact between the long side of an oval hot tub and either the decking or deck framing will prevent this.

Many people choose to have the top of the deck ¼" to ½" below the top of the hot tub. This helps to prevent dirt and debris on the deck from blowing into the hot tub.

An additional consideration is future access to the exterior of the hot tub. At some point in the future the exterior of the hot tub may need to be accessed for inspection, maintenance or possible for repairs. Dirt and debris should also be cleared out from around the sides and bottom of the hot tub. If a deck is going to completely seal in the hot tub, screwing down the decking, or providing a trap door or other type of access is advisable.

For some great design ideas be sure to see the picture gallery

General Maintenance Questions

OK, so you've decided that you don't want to spend the extra money on a chemical free water purifier, and you're going to do it the old fashioned way - with halogens. You go down to the big spa store and are overwhelmed with the different types of sanitizers. available.

Before we talk about how you get the stuff into the water, let's talk about the differences between chlorine and bromine. Both are halogens, although the use of bromine in pools and spas is much more recent than chlorine.

When bromine first came into vogue, in the early 1980's, it appeared to be the best thing for spas and hot tubs. It is more stable in water than chlorine since it has a very high evaporation point as compared to chlorine. Less of it escapes from the tub as a gas.

Bromine continues to sanitize the water even after it combines with organic compounds to form bromamines. When chlorine combines to form chloramines, they are at best a nuisance and just serve to sting your eyes and smell up your tub. Chloramines are eliminated either by draining and refilling the tub, or by shocking the water with fresh chlorine, which can be deadly to a natural wooden tub.

So, bromine seemed like a great thing when it first appeared. But then the industry started to pick up on the problems with bromine. It was so stable that it was difficult to get into the water. Erosion feeders needed to be supplied with a mixture of one third chlorine and two thirds bromine so the chlorine could give the bromine a "kick".

They're have also been reports that bromine is not as wide spectrum a sanitizer as chlorine. That is, there are some forms of organisms, most notably certain forms of either a black fungi or algae according to anecdotal reports, that are not susceptible to bromine.

Furthermore, because bromine is so stable, its odor is much more difficult to wash off the skin after bathing. And, those wonderful bromamines that maintained their ability to sanitize? It turns out that they are far more carcinogenic (cancer causing) than their chloramine cousins.

With chlorine there are three basic types, liquid, sodium-trichlor and sodium dichlor. The first two should only be used in swimming pools. Liquid chlorine will throw your pH so far out of wack it will be nearly impossible to balance your water. With the trichlor, the higher temperatures of hot tubs tends to make it a little caustic to your skin. If you choose to use chlorine, sodium-dichlor is the way to go.

The fact that both bromamines and chloramines are carcinogenic is reason enough to consider eliminating halogens with an ozonator. After years of experience, we have come to the opinion that if you must use halogens, granulated chlorine added manually is still the best method. This way, you have complete control over the process.

Regardless of which halogen you use and regardless of the method you employ to get it into the water, testing will be required to verify that the halogen levels are neither too high nor inadequate.

While ozone is a very powerful oxidizer, it's effectiveness in spas and hot tubs is still questioned by some "in the know". There's more in regards to that here. Regardless, ozone should not be used in wooden hot tub. Highly concentrated levels of ozone will accumulate on the surface of the water, beneath the cover, and will deteriorate the the upper area of the wood. Much more effective, and safer than ozone is an ionizer, which is included with every complete hot tub system.

The outside of a wooden hot tub doesn't require any type of treatment and nothing is required to extend it's lift. If desired for an aesthetic look, painting, staining or some other finish can be applied to match a surrounding deck. Nothing should be applied to the inside of the hot tub.

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