A design for small, low-cost demountable homes with full facilities (cooking, washing, shower and toilet).
© Plateau Group
This H4H design is available to any volunteer groups for non-commercial use, but please make a formal request.
H4H Fabrication Details
Hot water-tank and shower unit.
Also some metal fabrication details below,
[Highest Skill Level]
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:
We make a few suggestions here, but we don't pretend to have come to any real solution.
Tankless Electric Hotwater systemsOne of these is advertised for under a $100, as a "3800W Mini Electric Tankless Hot Water Heater Instant Heating Kitchen Bathroom Sink Tap Thermostat,110V/220V". It is a small unit which looks perfect, except for the fact that no mention is made of its ability to provide enough hot water for a shower. This may be a safety concern; having an electrical connection to a system of copper-pipes, water, and wet human bodies, does seem to us to be cause for careful consideration. Also a power requirement of nearly 4 thousand watts would put a load on any multiplexed electrical system with plug-in cables.
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:
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-showerThe best ready-made, heatable metal tank we have found is the standard 20 litre army Jerry can. These are rugged liquid containers made from pressed steel designed in Germany in the 1930s for military use. A large Jerry holds only 20 litres of water which is possibly just enough to give some sort of hot shower. But showers consume about a litre every six seconds, so 20 litres in only a couple of minutes at the most frugal limit.
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.]
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
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:
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.
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.
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:
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.
Plateau Group Convenor: Stewart Fist
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