This H4H design is available to any volunteer groups for non-commercial use, but please make a formal request.

[Highest Skill Level]

General Considerations

The provision of some sort of heated shower has given us more problems (and more failed solutions) than any other component in the cabin design. However we feel that it is essential to change the character of these small cabins from just a "shelter" to a home.

We have also decided to reject camping-type bottled gas or conventional gas heaters for basic reasons of safety in a ply-wood lined small cabin.

The problems are many but important points are:

• continuous flow hot water systems require large amounts of energy for short amounts of shower-time. They therefore put a very high load on the electric circuits, which is why instantaneous systems are generally gas, because this is capable of delivering short burst of intense heat.

  We could not find an electrical continuous flow device offering shower.

• Storage type systems can be light in their average energy load (while heavy in long-term costs). They also need heavy insulation to retain the heat when it is not being used, and in a small cabin in summer they will still be acting as heat radiators. So these are probably good in winter; bad in summer. Tank systems also need some way of moderating water temperature if they are not to be accident-causing scalding of the person entering the shower.

There are

We make a few suggestions here, but we don't pretend to have come to any real solution.

Tankless Electric Hotwater systems

Tank-type home water heaters

There is also a 25 litre, plug-in water heater for $400+ which will obviously not have the same heavy current load since it can heat over time. In case you'd forgotten your school physics: a litre of water weighs 1 kilogram, so we are talking real numbers when we consider hanging water tanks on a wall, etc. One value of this system is that the tank can sit on the floor of the unit; the disadvantage is the price.

The promotional material says it has a storage capacity of 31 litres, and can deliver 25 litres, with an energy requirement of 2.4kw. This is at a level where electricity can be delivered by a power cable with a standard plug -- it is just twice a small radiator.

Note that generally the capacity of any home hot-water storage system begins at 50 litre, and goes up into the family 400 litre range. We think 20 litres is an absolute minimum, and would prefer 25 to 30.

We assume that the difference between the quoted storage and delivery capacity would be a regulated requirement to ensure that six litres of water was always retained within the unit, so that it couldn't boil dry. The ads make no claims about temperature controls, either. But if you have this sort of money, it may be worth exploring further.

Making your own Hotwater System.

Plumbing components can be a very expensive ... and tradesmen's time even more so. Yet we feel that a hot-shower and the ability to have water on tap with both personal and clothes washing facilities are all essentials if the homeless are to retain their dignity.

We have looked at the possibility of an instant electric water heater, but have rejected these on the grounds of both expense and high power-demands. We also doubt that any mocked-up systems using electrical heating directly within the water would be safe in these circumstances.

The only safe way to heat water in these circumstances, appears to be to slowly heat a moderately-sized metal tank over the double-plate cooking unit. But this has problems also:
  • Water tanks are very heavy
  • Hot shower systems always have some safety heat control to guard against scalding.
  • Most systems provide ways to mix cold and hot-water.

This last is the one worth considering. However, we are going to refer only to the cheapest and simplest.

Turning a tank into a hot-water system:

The idea of a tank held above the kitchen bench area and heated by sliding a standard double-temperature electrical cooking device beneath, is the simplest, safest, and cheapest water heating and handling system we have come up with. It appears to be both electrically safe and able to deliver a reasonable hot shower (albeit for a short period of time), and we doubt that anyone will do much better.

Jerry-shower

Jerry Cans of this size are widely advertised overseas as military surplus at a cost of US$30, so they must be available in Australia for something similar in price. New ones are in the $80 range.

The advantage of the Jerry Can is that it has been designed and made for safety. It is rugged and has a good sealable cap which can be adapted in some sort of system like that proposed here.

The Concept and Some Principles

This is only a concept diagram, not necessarily to scale

Most of the solder-fittings and other components are readily obtainable in the gardening and plumbing section of a hardware store.

[Note: use metal ring-clamps on all pipe-to-hose connections, not the plastic ones.]
 

Water control:

There is only one tap which handles the water input ... plus a stop-cock to divert the hot-water to either the shower rose or to the basin. A similar device called a "diverter" can be used instead of the stop-cock.

There is a safety issue here. If the water tank is totally sealed, then someone will eventually go to sleep while waiting for the water to heat, and steam will build up and the tank will burst. This can be avoided by
  • Always leaving a open-path for the steam to the shower-rose. You can do this with a diverter (but check that it is either/or with no blocked position in the middle)
  • Or by using a stop-cock only on the basin distribution pipe.
  • In the CLOSED position, the water can only emerge at the shower-head at the highest point of the system. .
  • When the stop-cock is OPEN the water will flow out at the lower-level into the wash-basin.

This water will always take the lower-path if this output has less resistance to flow than the shower-rose, so use a wider pipe here. The flexible hose (clamped under the Cupboard doors) is probably the best output to the basin since it can be used to flush our bottles, etc. The shower-head is probably just a cheap garden watering wand; it neither needs or benefits from separate controls.

A single brass garden tap is therefore able to control flow to both the shower and the wash-basin depending on the position of the stop-cock. There are a range of diverters and stop-cocks in the plumbing section of any good hardware store, and many have standard pipe standard thread or pipe-solder fittings. The physical positioning of the stop-cock can virtually be anywhere along this flow and it can be fixed to the tank or to the Water Closet. You would always set it before getting into the shower.

The tap's position needs more consideration. It should be positioned at the level just above the Basin Drop-down door, and below the Cupboard hinged doors. In the earlier design we recommended fitting a standard brass-tap directly into the tank at about its mid-point. But we are now recommending against this because any entry-point into a home-made tank below the top level is probably a disaster waiting to happen.

The concept is this:

• Normally any shower system has a good temperature control so the water may be hot, but should never be scalding. Also cold and hot water are under separate controls, so the temperature can be moderated. This is not possible without adding more fittings here, and we are wary of having really hot water in any tank not commercially manufactured.
• However, if the brass garden tap was to be directly in contact with the hot water, it is almost impossible for anyone to scald themselves, because the tap will be too hot to handle. There is adequate warning.
• However we now think it is too risky to have pipes entering the sides of the tank. These fittings will necessarily be weak points unless the tanks are professionally fabricated and fittings can be brazed.
• The design concept here means that all pipes pass in and out of the tank only through a top-cap. This doesn't solve all the problems, but it solves the potentially serious ones.
  • Consequently, if the input pipe fractures or the hose dislodges, only half the tank water can siphon out.
  • If the stop-cock is accidentally left open, only a third can siphon out. Normally nothing will come out accidentally.
  • The input pipe can now afford to have a spray (a partly crush end of the pipe) down at the one-third level where the cold and newly heated water will be forced to intermix by the turmoil.
  • By taking the output from the two-thirds level, it will bypass the really hot water collected at the top. By the time the hot shower is nearing its end the water temperature should be moderated through mixing.

We strongly recommend this approach. It does mean that the ideal location for the tap should he hard against the outside of the tank, so the hand will detect the water temperature at close to the level where the shower-water is being harvested. This can probably be best done by the use of Araldite and some clips to attach it to the sides of the tank, but check that the basin and toilet doors open before you take this step.

Miscellaneous

• Because of the weight of water, the water tank must have a strong metal stand at the water-closet end of the kitchen bench (Between Studs 5 and 6). If the tank is relatively light in weight, this stand can probably be entirely carried by the wall studs and the kitchen bench (which is, itself part-carried by a batten on the side of the Water-closet.
• When hot-water is wanted, the cooking hot-plate can now be repositioned along the bench beneath the tank. Dual hot-plates have both 600 Watt and 1000 Watt heating elements.

Another possibility: It has been suggested that a small water tank with the water passing through a submerged coil of copper pipe might be even better. The water enters via the lone tap, but it then passes through the coil and emerges at the other end into the diverter. The idea is to use a small amount of very hot water in the tank as a heat-exchange.
    The tap still controls the input to the pipe coil which then feeds directly out via the diverter at the top. The trick is this: a small hole (1 or 2mm?) is drilled into both the bottom and top of the coil, so there is always some exchange of hot water between the pipe and the tank, and hot water will always leaks from the tank into the pipe. This small volume of tank water then provides as much thermal mass as a large tank. In theory, the scalding-hot water in the small tank will warm the moving water passing through the coil, providing a much longer warm shower.
    It's an idea that definitely needs testing because if it worked, the smaller tank capacity needed could sit directly onto the hot-plate.

Tank Making

Making your own tank is not a task for the unskilled, but plenty of handymen will be able to add both a flat gal-iron bottom and a lid to short lengths of industrial galvanised air ducting pipes (for office air-conditioning). You can buy both circular-section ducting and square/rectangular shapes: circular is best because square will tend to bulge (you may need to add some horizontal strengthening baffles half-way up).

If you attempt this and don't have access to brazing tools you will need to seal the joints with solder. We believe that this is OK provided there is no direct heat on the tank when it is empty; so the system must ensure that the tank always contains water and that it is never entirely sealed. For this reason we advocate a stop-cock only on the wash-basin outlet, so that the shower rose is always open.

Here are some useful ideas about tank-making:

• Make matching top and bottom end-domes, each with 20mm flanged edges for pop-riveting.
• Use only galvanised pop-rivets (not the normal aluminium).
• Add the bottom to the tank first. The dome should curve up ... thus creating a heat cavity and keeping the rivet holes below the water level.
• Use plenty of rivets, especially around the bottom plate.
• You can now solder the inside side/bottom junction relatively easily provided the tank is not much more than an arm's-length in height. You will be working from inside the tank with a small blowtorch.
• Think about adding cross-bracing/baffle half-way up if you are using rectangular ducting.
• Now add the top dome with some sort of sealable screw-lid -- it should be large enough for a couple of pipe entries. The dome in this case should curve upwards also, but you'll need to use fewer rivets. You will then solder over each one since these are subject to water leaks.
• You can now easily run around the top-rim with solder, provided you have left a few millimetres of the sides projecting.

Tank Stand

The Water Tank needs to be raised about 25cms above the WC end of the Kitchen Bench so that the electric hot-plate can slide beneath.

Any water tank capable of giving a shower will require a relatively strong stand, and the type illustrated here is probably acceptable only for a small or medium-sized tank, however the further back the weight is, the stronger the stand will be (relatively). We think a stand like this would safely carry a Jerry can with only its 20 litres (20 kilograms) of water.

This could be made out of a single 1.2m length of angle (possibly the perforated angle iron sold for display stands), and it should fit tightly between Studs 5 and 6. Of course it could also be supported by angle-iron legs on the Divider Cupboard side which go down to the floor.