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Notes on ConFest Hot Tub construction

by Dave Symons

Here are some hints, tips and notes on the subject that I have gathered from experience obtained over several festivals.

Location Location Location

• If a major leak, or overflow (usually from too many people entering the tub and causing the water level to rise) occurs who's camp is it going to flood? Noise is also a factor. If it is right next to your tent it will keep you awake with people talking all night. If it is too far away from your camp it may get damaged by "kids" when the tub is unattended. Other factors to consider are shade, overhead trees, privacy and most importantly, drainage.
  
  

Drainage

• If you are not prepared to chlorinate (yuk) the tub every day then it will need to be drained, cleaned and re-filled every day. Otherwise it will end up with the consistency of soup or a mud puddle with a layer of sludge on the bottom and will smell like a cesspool. I personally do not like bathing in someone else's dirty bath water. Cleaning every day keeps it reasonably fresh. Hence the need for easy drainage.
  
  There are 2 ways to drain the tub:
  
  
  1. By siphon. Build the tub on a rise with a short nearby dip to a point lower than the anticipated base of the tub. The final draining place (river, swamp) should be within a reasonable range (50m) and lower than the tub. A short piece of 1" poly pipe (8' - 10') can be used to start a siphon then it can be joined (by a screw type fitting) to a longer piece running the final distance. The final drain pipe should not at any time run higher than the level of the tub's base.
     
     
  2. By pump if you have access to one - usually more trouble than it is worth if you don't because someone will always want to borrow it for somewhere else and you will constantly have to chase it.
     
     

Tub Construction

• 2' x 6' x 8' is a good size. 8' x 8' works okay. So does 6' x 10'. 6' wide makes it comfortable for foot massaging. The larger the size the more difficult it is to heat. The smaller, the more crowded and uncomfortable it can be. The depth is an important factor in determining boiler design and its height above the fire.
  
  
• The tub must be built with enough strength to withstand the internal water pressure and people sitting on the sides. A tub 2' x 6' x 8' full of water will weigh in excess of 2.5 tonnes. Poorly constructed sides will bend bow and even burst. If galvanised iron sheet, pop rivets, timber and nails is used then some vertical struts will be needed to reinforce the sides along with top and bottom rails.
  
  5-ply with a 3"x1" frame around the edges works well. The better designs allow for the tub to be easily bolted together and disassembled allowing for easier transportation and re-use. Another point for consideration is to allow a flat top edge around the tub for guests to place their drinks, etc and sit on. This will need to be strong enough to support them as well.
  
  
• There are several methods for sealing tubs. Two of the following methods used together works well.
  
  
  1. A polythene plastic sheet. It is prone to developing small leaks. At least 2 layers are required and you will need to make daily repairs and/or replacement. Beware of pipes and buckets that may damage the liner. If the tub is constructed without a base then a layer of sand (free from sharp objects) and a couple of additional layers of polythene covering will also be required. Polythene sheet can be held in place by nailing it down along with the top "beading/decking, or by tying a rope around the tub to hold it in place.
     
     
  2. Silicone sealant. Silicone is prone to damage by the walls of the tub moving due to water pressure or whatever. Can also get damaged by "kids" picking at it.
     
     
  3. Strips of bandage made from an old sheet and quick drying oil paint. At least 2 litres of paint will be required. I found this method to be reliable but is also prone to being picked at.
     
     
  4. Grey tape or "gaffer" or "duct" tape can be used for fixing some small leaks.
     
     

Boiler Design

• Many designs have been tried over several festivals. Some ideas have been steel buckets of water on a fire, car radiators and fuel tanks and 44 gallon (200 litre) drums. The 44 gallon drum seems to work reasonably effectively, is relatively simple to use and is not difficult to obtain at ConFest. Old burnt drums can sometimes rust inside and need to be thoroughly flushed out. If a treacle drum is used the water will become discoloured for the duration of the first fill (this is not a real problem). Old fuel drums will need to be burnt for several hours prior to filling.
  
  
• The drum can be suspended above a fire by use of star pickets and fencing wire. If the drum is too low, a fire pit can be dug. If the drum is too high, the fire can be raised by using a "half 44" and suspending it at the right height with fencing wire also. This later method is undesirable as it is awkward to work with in maintaining the fire and is also less efficient. Having a fire at ground level is the simplest and will work well with a 2' deep tub.
  
  
• The boiler will need to be reasonably close to the tub to eliminate heat loss through the pipes and far enough a way to not be a safety and smoke hazard when walking around the tub.
  
  

Water Level

• To avoid problems the water level in the boiler will need to be set to be higher than the top lip of the tub.
  
  
  
  
  44 gallon drums have two openings that will accommodate a 2" and a 3/4" o.d. tapped steel pipe. Steel pipe is needed to carry the water away from the heat of the fire then poly pipe can be used. Most poly pipe fittings are available from the festival pool otherwise they are extremely cheap and easy to purchase if necessary. The 2" port should be used for the outlet into the tub to encourage a greater flow rate out than in. The water level inside the boiler will need to be set. If it is too low it will be inefficient and may burn out the drum. If it is too high it will take too much fuel to maintain the heat. The boilers internal water level can be adjusted (when empty as it is too heavy to work with when it is full) by rotating the drum so that the water "overflows" out of the 2" outlet. The bottom lip of this outlet should be positioned somewhere around one half to two thirds of the way up the drum, and at a height somewhere between 1" to 6" above the level of the top of the tub (and the pipe to the tub is run below this level). The higher of these measurements is recommended to allow for the fencing wire to stretch in and the pickets to sink under the weight of the water. Positioning the outlet higher will make it more difficult to manually fill the boiler as one has to lift the water higher and creating more work than is necessary. Setting the outlet too low may cause back flow when the water level in the tub rises above the level in the drum.
  
  

Boiler Siphoning

• If a sealed pipe is used between the boiler and the tub and the end is completely submerged into the tub, a siphon effect will drain the boiler down to the water level in the tub causing frustrating problems in maintaining the tub's operation. This can be overcome by providing some type of vent in the pipe. Allowing the pipe to just flow or tip over the edge of the tub will solve the problem but can be a safety hazard. Using a "T" piece pipe fitting at the edge of the tub where the boiler flows into the tub, with a pipe flowing downwards into the water and a breather or steam vent pipe rising upwards and away, will solve the problem.
  
  

Steam Venting

• Some type of steam vent will be required to prevent steam from building up pressure inside the drum. Steam pressure causes water flow problems and can also can be a safety hazard due to hot spattering water. A simple method is to use a "T" piece pipe fitting at the edge of the tub where the boiler flows into the tub as described previously. Alternatively a 1" square hole can be pierced into the top of the drum. This method is not desirable as it "damages" the drum and prevents it from being useful for some other purposes. Other designs for steam vents have been tried using a "T" section at the 2" outlet or elbow. This can create problems if the vent is not wide, or high enough and if a drum overflow occurs.
  
  

Overflow Problems

• Overflowing the boiler creates problems as it puts the fire out and wets the ground around the pickets, causing the whole assembly to sink and stuffing up the water level adjustments. Also all pipe fittings should be made thoroughly leak proof for the same reasons (use of plenty of teflon tape is recommended). The best way to stop overflowing is to organise the flow so that the boiler drains faster than it can be filled. Using the 2" port for the outlet and the 3/4" for the inlet will go most of the way in curing this problem assuming that pipe with a minimum diameter of 1" is used throughout. The pipe from the outlet to the tub should be as wide and as free of restrictions as possible. Consideration should be taken as to the positioning of the tub end of this pipe as it is a safety hazard.
  
  

Filling & Heating

• There are many ways to fill the boiler. Some methods that have been tried are by pumping in river water through a hole cut into the top of the drum, using hand or electric solar powered pumps to circulate the water or by using one of the existing ports on the drum. Using the 3/4" inlet is the best. Pouring it in the steam vent will also work, although it is smoky and the hose gets hot. A pump of some description can also be used. The simplest and easiest method is to use a half "44" hopper next to the tub. The trick is to find a "half 44" with a threaded hole in the correct position at the bottom. It will need to be within easy reach of the tub to allow it to be filled by bucket from the tub. It will need to be high enough to be above the boilers water level and provide good flow (6" or more is good) and low enough to be able to manually bucket the water out of the tub without much effort. Peter Cruise made the comment at Easter 97 that pouring 5 buckets in 1 minute will move the same amount of water that an electric pump will circulate in an hour and it doesn't need batteries.
  
  
• The tub can be filled from any water source. Connecting to the festival water supply will work although there may be insufficient pressure during the peak daylight hours to be really effective (if it is required to be filled during those hours). A 1/2 inch outlet should be used to avoid placing unnecessary strain on the rest of the system. Another alternative is to independently pump from the river. The tub should be filled by carefully running it through the pre-filled and heated boiler via the hopper while stoking the fire. A large fire (flame right around both sides of the drum) is needed for the initial fill and care must be made not to flood the boiler with cold water at a rate faster than it can heat, or to overflow the hopper. The fire can be shrouded with spare sheet metal or corrugated iron for increased efficiency, safety from the wind and smoke and to protect the surroundings (poly pipe fittings) from the heat of the fire. A fully enclosed boiler can be run on days of total fire ban with out any problems. this requires a more elaborate construction. The tub may take somewhere between 2 - 4 hours to fill to a level sufficient for use (6"- 8") and a few more hours to slowly fill it to the desired level. Filling all the way to the top is not recommended as the tub will overflow with the addition of several bodies. Around (4"- 7") below the top is sufficient. Once the tub is at the desired temperature the fire will not need to be large to maintain the heat and the only fire necessary will be a small one that just needs to be kept alive. A recent experiment was to shroud the fire with concrete bricks. This was extremely effective as it acted as a heat bank and resulted in a tub that was continuously extremely hot. A sheet of bubble-pak or polystyrene foam can be floated on top of the water in the tub to keep the heat in when the tub is filling or not in use. Polystyrene foam will leave a residue of small beads floating in the water and bubble pack will introduce foreign dirt to the tub if it is left lying on the ground when it is not being used. Hanging bubble pack on a rope line solves this problem.
  
  

Cleaning

• After all that work it can be frustrating to see dozen's of enthusiastic people proceed to climb in with dirty feet. Surrounding the tub with carpet and a foot bath helps to solve this problem although it still requires some means of educating tub guests to use them correctly. Foot baths need to be washed out and replaced regularly along with the carpet swept daily. Experience has shown that it is practical to drain the tub for cleaning in the late afternoon to allow for cleaning and gathering of fire wood prior to sunset. The subsequent after dark water pressure rise will be sufficient to re-fill the tub ready (for you to be first in) sometime in the early evening.
  
  
• Tub draining as previously mentioned can by done by several methods. If a siphon method is used the resulting suction can be used to "vacuum" the layer of "sediment" off the bottom, however this can also result in damage to any polythene liner. What is required is some kind of mop attachment that can be attached to the end of the suction line to allow for effective vacuuming without damaging the liner. A solution to this is still in the conception stage and suggestions are welcome.
  
  

Conclusion

• Building a tub can take considerable time. The majority of the time taken at ConFest seems to be scrounging the necessary tools and or equipment. Once everything is brought into the one place the actual assembly is reasonably quick and can be completed within a couple of hours. Building the tub itself can take lots of time and I would recommend construction of "bolt together" types be carried out prior to arriving at ConFest.
  
  
• The task of cleaning, filling, sweeping carpet, rinsing footbaths and gathering fire wood etc. takes considerable work and is too much work for one person for the duration of a festival if that person has a desire to experience some of the rest of the festival. A good well maintained tub would be more easily provided by a "village" with a few "in the know" volunteer workers that can help each other to distribute the workload.
  
  

Happy Tubbing : )
Dave Symons
30/10/98

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