Cowboy Hot Tub Heater Installation and Users Guide

Revision 2.0

May 2, 2003

Copyright 2003 by Rick Ryen



Congratulations on your purchase of the Cowboy Hot Tub Heater. This unit should give you years of satisfying service if you follow these simple guidelines for proper use and maintenance.


More information can be found at our website at


We recommend that you read and understand this document in its entirety before using your tub.


Stainless steel version

Warnings and Cautions. 3

Additional items you will need. 4

A tub. 4

A proper flue pipe. 4

Weight and Buoyancy considerations. 5

Options. 5

Top covers and Insulation: 5

Installation and Setup. 6

Fuels. 6

Preparing your fuel: 7


How to operate: 7

Starting a wood fire: 7

Reversing the flow of exhaust 8

Useful starting tools. 8


Long tipped butane lighter 8

Hot coals starting method: 8

Regulating the fire: 8

Keeping the water clean: 9

Periodic maintenance. 9

Other interesting sites. 10


Warnings and Cautions


Always operate heater at least half way submerged, up to where the 3 1/2-inch pipe starts.


Do not allow heater to fill up with water and then freeze.


A wood fire should never be left unattended.


The flue pipe and certain upper parts of stove chimney get extremely HOT. Do not reach around the chimney to get that piece of wood, your arm will touch the chimney and sizzle. Respect that chimney; it is hot and will burn you in an instant. It is recommended that you purchase from me or from Summit Racing part # THE-11152 hedder wrap. It is fiberglass tape used to wrap automotive exhaust. Start wrapping the 4-inch pipe where it is level with the rectangle box. Wrap up 12 to 18 inches or as high as you think you might come in contact with the pipe. There is no need to wrap the section of pipe that is in contact with water. A hose clamp for a 4-inch pipe is needed to hold the tape in place at one end; the other end will hold itself in place. DO not touch the submerged parts of the heater when it is burning. Although they are not nearly as hot as the flue, they still may be hot enough to cause burns.


Tubing dehydrates you. Stay hydrated by drinking plenty of water before, while, and after using the tub.


Use caution while drinking alcohol. The alcohol will further dehydrate you and impair judgment.


When exiting a hot tub use caution. As you stand up you may get lightheaded. Hold on to the side of the tub as you exit it. This will only last for a couple of seconds. Use caution to avoid losing your balance and falling.


Do not install the hot tub, with its massive weight, on decks or structures that are not designed for it. If in doubt, seek the assistance of a structural engineer. The 150-gallon tub with water, heater and people may exceed 1500 lbs. Remember water weighs 8 lbs to the gallon.


Any wood-burning appliance can be dangerous if misused. Hot water and hot metal can cause injury; this is not a toy for children. If you are going to allow your children to hot tub, heat the tub up for them and remove the heater before letting them get in. It is your responsibility to supervise! Drowning is a possibility even in a five-gallon bucket.


Do not use any liquid or gaseous fuels as fuel or to assist in starting your heater. Contact me personally, Brek at if you wish to use a fuel other than wood.


The maximum recommended temperature for hot tub water by most manufacturers is 104 degrees;however, 106 degrees F may be tolerated by fit individuals for short periods of time. Use caution and exercise good judgment.  Use of an accurate thermometer is recommended as well as an awareness of your own ability to handle high temperatures.


Additional items you will need:


A tub


The Cowboy hot tub was designed for use in a 150-gallon Rubbermaid brand stock tank. These rugged oval shaped tanks intended for watering livestock, will accommodate up to two adults when used as a hot tub. They can be found at many agricultural supply stores for about $150. Other types and sizes of tubs may be used. The design features described here refer to the use of the heater in the Rubbermaid 150-gallon tank. The considerations may be useful if you are adapting the heater for other tank types.


The Cowboy Hot Tub heater has two steel rods that hook over the edge of the long side of the Rubbermaid 150-gallon tanks. These provide the main support for the heater. The heater should be plumb and level as it sits in the tank. This is especially important to ensure that the additional weight of a chimney is balanced and not subject to tipping.


A proper flue pipe

It is recommended that you purchase a smoke stack from Cowboy Hot Tubs.


It is important to have the proper flue pipe for the heater to work correctly.


A proper flue pipe for the heater will be a 4-inch piece of tubing or pipe at least 8 feet long that weighs at least 20 lbs.


It is very important that your chimney weigh the 20 lbs. This weight is necessary to counter buoyancy from the heater being submerged in water. 


The flue pipe stub welded to the heater has a 3.5-inch outside diameter.


Simply slide the 4-inch pipe over the pipe stub on the heater.

Anything less than 6 ft of chimney and you wont really have enough draft. With a short stack you will be disappointed with the rate of burn and the time it takes to heat your tub.


It is recommended that you purchase from me or from Summit Racing part # THE-11152 hedder wrap. It is fiberglass tape used to wrap automotive exhaust. Start wrapping the 4-inch pipe where it is level with the rectangle box. Wrap up 12 to 18 inches or as high as you think you might come in contact with the pipe. There is no need to wrap the section of pipe that is in contact with water. A hose clamp for a 4-inch pipe is helpful to hold the tape in place; wire will work in a pinch. 


Sparks From the Flue:

    Personally this has never been a problem for me. I have used the heater in a suburban setting and in areas with dry brush around. Split 2x4s is my main fuel. The few sparks that come out of the flue usually extinguish themselves before hitting the ground. If conditions are such that you would not barbeque, then you probably shouldnt hot tub either. Get experience with your heater and the wood you are using in a safe area. Of course it could never hurt to have a fire extinguisher handy. At least have a bucket handy, as you will for sure have a tub of water available.

    If you are in an area prone to wild fires, you might consider adding some spark arresting mesh on the top of the flue. It is mainly intended to prevent light fly ash, such as that caused by burning paper from exiting the flue and causing a wild fire. Use in national forest areas may require this type of device.


Weight and Buoyancy considerations

The flue pipe needs to weigh at least 20 lbs. If your chimney weighs less than 20 lbs, your heater may become buoyant when a person enters the tub raising the water level. If this happens the heater will rise up and fall over. This may result in personal injury and a mess in your tub. Use caution the first couple of times you use your new tub and heater. In short order you will become a professional wood burning hot tuber.


Always keep an eye on the heater when entering or leaving the tub and be prepared for the possibility of buoyant tip-over, especially the first few times the tub is used with a different flue pipe. The heater has been engineered so this does not happen, but still use caution. With a 20 pound flue pipe the heater should stay in place even if the tub overflows.



Top covers and Insulation:

Your hot tub will heat up faster and stay hot longer if you provide insulation.


The tub looses heat the fastest from the top surface of the water. This heat loss can be minimized by fabricating an insulated top cover for your tub.  A tub cover will also reduce the contamination of the water from falling leaves, flying insects, pollen, and ash. Without a cover you will have ash in your water.


Rigid closed cell Styrofoam insulation can be used to fabricate an insulating top cover. This material can be found at most building supply outlets. It comes in two-inch thick sheets 2 feet wide by 8 feet long and costs about $9 a sheet. Look for the blue or pink types. The white Styrofoam may be a bit less expensive but it breaks easier. The foam panels can be cut with a serrated kitchen knife or box cutter, and can be glued with construction such as Liquid Nails brand. Latex paint can be used to apply a more pleasing color.


You might consider making your top cover in two sections. One section might cover 1/3 and the other section the remainder..  You might cut an opening for the heater in the 2/3 section, making sure that no part of the cover comes into contact with hot sections of the heater.


Leave the 2/3 section in place while tubing to minimize heat loss. You can also use this as a shelf to place your beverage glass.


The tub will benefit from the addition of insulation in the sides as well. This is especially true if you will be using your tub in colder climates. Cold climates would be defined as tubing temperatures below freezing.  How you accomplish this depends on your inventiveness and resources.


One creative customer suggested a wooden skirt made of back-insulated boards with a rope woven through the boards to attach it to the tub. You might fabricate a simple wooden box frame with 2x2 lumber, plywood and insulate the inside of that with 2 foam panels. If you are not too fussy about appearances, you might consider spearing on a layer of Great-Stuff brand foam insulation that can be acquired at building supply outlets.


You dont have to take any insulating steps to start enjoying your Cowboy hot tub right now, but adding a top cover and insulation will greatly improve the utility of your tub and enhance your hot tubing experience.


Installation and Setup:


The first order of business is to select an appropriate spot for your tub. You will need a firm level area that is capable of supporting the weight of the tub. Water weighs over 8 pounds per gallon, which means that 150-gallon tub with heater, flue pipe, and number of people may exceed 1500 lbs. Do not install the tub anywhere other than the earth unless you have determined that it will support this weight.


The stove may emit small amounts of sparks or bits of burning ash. Keep the tub well away from the eves of your house, trees, or other combustibles. You should locate the tub near an area where you can store your fuel and keep it dry, and also in an area where you can safely dispose of ash.


Make sure the location has a suitable area where you can drain the tub, and also have a ready supply of water (garden hose) for refilling. You will probably drain and refill your tub on a minimum of a weekly basis.




The Cowboy Hot Tub Heater is designed to burn wood. Although the use of other fuels may be possible, their use may be dangerous and is not recommended. The uses of liquid or gaseous fuels are especially dangerous. Under no circumstances should gasoline be used to start or to fuel your heater. You are responsible for your own actions.


Preparing your fuel


This heater is designed for wood burning. The ideal wood fuel would be a 2x4 a foot long split into 2 or 3 pieces, dry of course. Any moisture that is in the wood will take heat away from your fire. Dry wood is very important. Stack your wood vertically in the rectangle box.  When splitting your wood do so during the day in a proper place. Do not split your wood hastily at night. It is easy to have an accident with your hatchet; be careful. The best size of wood is approximately 12 inches long with a diameter of 1 inch. The shape of the firebox will accommodate this size wood in the vertical position. Thinner and shorter pieces may make getting a fire started easier.

You will need approximately 15 pounds of wood or a 5-gallon bucket full for a single tub heating session. It is always preferable to have too much fuel stockpiled than too little.


Avoid using painted wood or wood treated with preservatives. These will produce noxious fumes that may be hazardous to your health and may burn unpredictably.


How to operate:


Starting a wood fire


In starting, the air may flow down the chimney and up through the rectangular opening, or the air may flow down through the rectangular hole, and up the chimney. Sometimes you have to start the fire in reverse.  If you start the fire in reverse, you might follow these steps:

1.      Start by making ten loosely balled up sheets of newspaper (avoid using the glossy coated sheets). Light one and drop it into the bottom of the stove.

A.  If the flames are coming up the rectangle box, drop in a couple more balls of paper. Drop a few thin pieces of wood on top of the newspaper. 

      B.  Slowly feed in more wood until you have the wood burning.

      C.  You dont need a raging fire, just an established one. Attempt to reverse the airflow by blowing on it.

2.      If the flames from the first ball of paper start going up the chimney, the forward and correct airflow, add a couple more balls of paper.

A.     Add some wood on the side of the rectangle box.

B.    With the flow in the correct direction, the idea is to get some wood in the box with some burning paper behind it, thus allowing the flames from the paper to flow over the wood.

Reversing the flow of exhaust

If your airflow did not start immediately flowing into the box and up the smoke stack, you will have to reverse the flow. Initially, the exhaust flow may be operating in reverse, with hot gasses exiting upward through the rectangular hole. This is ok; allow this to go on long enough that a fire is established. Do not attempted to heat the tub in this manner though. Simply blow into the rectangle box and the airflow should reverse and continue that way. Once proper airflow is established add more wood, fill up the box. Never force wood into the box. This will result in too much wood being at the bottom of the box and blocking the proper airflow. The wood needs to be able to fall as it burns. Forcing wood in will also cause it to hang up and not fall to the bottom where the burning takes place. If you do get too much wood at the bottom, try to take a stick and make an air pathway at the bottom somewhere.

Useful starting tools

Long tipped butane lighter:


You may find that a long tipped butane lighter, as is used for lighting gas grills. to be a useful tool in getting your paper started.


Garden torch method:

     Harbor Freight offers a three-foot propane torch attached to a small screw on a propane bottle. It is called the garden torch. This thing makes starting the heater as easy as can be. Fire up the torch, insert into the  bottom of the heater, directing the flame towards the smoke stack. The flow should start immediately. Throw some paper and wood in and ignite with the torch. This beats any other method of getting your heater started!

Hot coals starting method:


One highly effective means to start your heater and establish the forward flow of exhaust up the flue pipe is to use pre-heated coals or burning embers. Gather hot embers or charcoal that has been ignited and brought up to a glowing red temperature from another fire, such as a charcoal grill or fire-pit. Clearly, you must use extreme caution here not to spill hot coals on the carpet or other combustibles! Carefully dump a small shovel of these hot embers into the bottom of your Cowboy Hot Tub Heater being careful not to spill any ash into the water or to obstruct the free flow of air to the flue. The correct airflow should start immediately. Put wood into the box, it should start to burn immediately.

Regulating the fire


The rate of burn can be regulated by adjusting the intake of air through the rectangular feed opening. To slow the rate of burn, partially cover the rectangular opening with a piece of sheet metal or board. 


Check the level of fuel periodically to insure that you have sufficient fuel to continue the burn until the tub comes up to temperature. You should check on your heater every 20 minutes for fueling.


Organize your bathing suit (optional), bath towels, and refreshments when the temperature gets around 100 degrees Fahrenheit. The typical maximum temperature for comfortable tubing is 104 degrees Fahrenheit, depending on personal preferences and physical fitness. The very old and young children are more susceptible to burning and problems caused by excessive heat. Use caution before entering a hot tub.


Floating hot tub thermometers are an important safety and comfort tool that can enhance your tubing experience.


Keeping the water clean

Microbial life forms will grow in untreated and unfiltered water. There are various approaches you can take to avoid bathing in water that has become contaminated by bacteria or algae. The safest method is to replace water after each use, as you do in a normal bathtub.  My tub being in Southern California is good for around 3 uses. A cup of bleach and a cover can extend this. Since I have a hose and a pump the water just gets changed.

The Rubbermaid brand stock tanks have a drain near the bottom of the tub. This makes draining easy. You might consider adding a length of pipe or getting the fittings to attach a garden hose to direct the water away from the tubing area, and to prevent mudding. It is helpful to have a pump to empty the tub. We offer a pump that attaches to a garden hose. Hook the pump up, water your lawn for about 10 minutes, your tub will be empty and you will have recycled your water. 


Taking a shower before hut tubing can be one method of eliminating a source of contamination and extending the life of a fill. Of course you can shower at your tub with a bucket in less than a minute.

Periodic maintenance

You will find either variant of Cowboy Hot Tub Heater to be surprisingly maintenance free. The stainless steel version has the advantage to be corrosion resistant. The painted steel version will require a bit more periodic maintenance to keep it in tip- top shape.


Do not allow water from rain or other sources to accumulate in the heater. This will make starting a fire difficult or impossible, and will make cleaning out any ash residue difficult and dirty. Should water freeze in the heater, it may damage the heater. It is best to remove the heater from the tub and store it under cover and away from moisture when not in use.


Flue pipes may become rusty with use and exposure to moisture and the elements. A periodic (seasonal) repainting with high temperature paint such as used on gas grills can keep your flue pipe looking good. A stainless steel flue will last forever, and you can polish the outside to make it look new again with some steel wool.


For the steel model, the application of high temperature paint periodically will help to protect the stove. Remove any corrosion with a wire brush, clean well of all dust and grease, and then apply a thick coat of paint.


Other interesting sites


We are confident that our product is one of the best and most cost effective out there. We encourage our customers to find creative uses, customize, and share their experiences with others.


We encourage this interaction with our web site at


You may find our products offered for auction at from time to time.


You can see how we compare to our competition by visiting


There is an interesting hot tub experimenter site at Hes not a customer, but he should be!


You can add some discussion about homemade hot tubs at google groups.