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Notes on ConFest Hot Tub construction
by Dave Symons
30/10/98
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:
- 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.
- 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.
- 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.
- 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.
- 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.
- 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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