Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way

Cob bathroom build – the plumbing and electrics

It seems crazy that 2 months have gone by since I last posted about the cob bathroom we’re building here. Facebook followers will know where we are with it, but the blog is long overdue an update.

After completing the post and beam framework and the roof, the next step was to complete the plumbing and the rest of the electrics.


The hot water in the bathroom is provided by a wood-fired 150-litre Portuguese-made insulated water heater or bailarina. I’d originally planned on a second-hand German Badeofen, which is pretty much the same thing, as for many years there has been a good local source of them. But good ones are getting harder and harder to find now and many have cracks or corrosion in the cylinders. However the same style of water heaters are still being made in Portugal, and although not always easy to find, can be sourced relatively easily once you know where to look. They’re not as cheap as a second-hand one clearly, but there’s a lot to be said for buying new when you’re playing with fire and hot water under pressure …

The bailarina - our 150-litre Portuguese-made wood-fired water heater

The bailarina's firebox - our 150-litre Portuguese-made wood-fired water heater

This one was ordered in July but with August being a holiday month, we had to wait until well into September before it finally arrived. It comes with two temperature gauges (which are fitted near the top and lower centre of the tank and provide a good indication of how much hot water you have in the tank as well as its temperature), a sacrificial anode and a pressure release valve.

The way it works is very simple. It’s basically a large Kelly kettle. The cold water feed brings cold water into the bottom of the tank and hot water exits from the top. The fire is lit in the bottom firebox and the hot water cylinder surrounds the central flue. With the coldest water being closest to the fire, the water heats pretty evenly and quickly on just an armful of firewood.

The bailarina - our 150-litre Portuguese-made wood-fired water heater

We could have built a rocket stove water heater (and plan to for the bathroom that will be attached to the greenhouse) but for this bathroom it simply wasn’t right for the space. The beauty of the bailarina/Badeofen design is that the heat source and hot water storage are integrated into the one unit. This one only has a footprint of just over 500mm diameter, perfect for a small bathroom, and even though insulated, still provides enough heat to warm the room as well. The insulation is very efficient: water is still warm 48 hours after lighting the fire.

The plumbing is arranged so that in Summer we can switch over to solar-heated water. We won’t be building this on until next Spring now, but the design of the collector is a very simple one based on a large coil of black plastic pipe.


Electricity in the bathroom comes from our batteries, so we’ve used LED lighting throughout. Most of the light is provided by high-power 3-LED bulbs: 3 downlighters over the basin and 2 globe lights over the bath and toilet. A slight extravagance in terms of power, perhaps, but I also had this idea I wanted to try with a 5m strip of LEDs …

This is a cob building: buried bottles in the walls are de rigeur! While feeling slightly ambivalent about that ‘uniform’ sense to them, I do like them – they’re fun, they’re recycling, and they provide extra light during the day, particularly useful in areas like bathrooms and toilets where you want light without a see-through light source. But I’m less keen on some of the more free-style installations I’ve seen as my taste leans more towards clean, understated and simple designs. And there’s that question over what to do at the bottle neck end. And how to accommodate fixed-size bottles in varying wall thicknesses. And they’re not much use at night.

So I had an idea to solve all that in one go by using pairs of 20cl beer bottles placed neck to neck inside reflective tubes which contain a small number of LED lights, with the tubes attached to a framework so the design could be preformed easily and not lost in the craziness of cobbing. Using reflective tubes between two bottles means minimal light loss and gives the flexibility to accommodate different wall thicknesses by adjusting the length of the tube. And the LED light strips make them just as useful at night.

The reflective tubes were made from a length of plastic waste pipe, the diameter selected to be as tight a fit as possible around the bottles. I lined the cut lengths of pipe with self-adhesive aluminium foil tape.

Making reflective tubes for bottle lights

The tubes were then mounted either side of a length of wood using galvanised wire. The design was conceived as ‘waterfalls’ of light which would be falling down the two external walls of the toilet area.

Mounting reflective tubes for bottle lights

LED light strips were wired and stuck into the reflective tubes and the whole assembly fixed in its final position ready for the bottles and the cob. Each set of LED light strips are connected via junction boxes fixed onto wooden frames to a single 12V transformer.

LED light strips inside reflective tubes for bottle lights

Mounted reflective tubes in positions and ready for bottles

Bottles were placed neck to neck inside the tubes and stuck with the same self-adhesive aluminium tape.

Bottles fixed to reflective tubes for bottle lights

Once in position, the lights are clearly visible through the bottles.

Bottle lights

Once we started cobbing the walls, the bottle framework made it very simple to keep the bottles in the right position and the electrical connections intact while the cob was worked in around them.

Bottle lights on framework during cobbing

Bottle lights on framework during cobbing

The bottle-light ‘waterfalls’ descend from a single piece of cordwood on the side wall, and a window created from a woodpecker-hollowed piece of chestnut on the front wall.

Bottle lights on framework during cobbing

Here is the finished result. The ‘rain-chain’ is also made from the tops of the same beer bottles. The bases of the bottles will be used in an internal wall, stuck end to end with self-adhesive aluminium foil tape, to create an division between the bath and the toilet. But construction will have to wait a while – we haven’t quite drunk enough beer yet …

Bottle lights in cob wall

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  1. Paul March 12, 2013


    Can you tell me where to find the wood-fired 150-litre Portuguese-made insulated water heater or bailarina? What does this cost?

    Looking forward to your reply,


  2. Quinta do Vale March 12, 2013

    Hi Paul. First I asked my local builders merchant to get one but he had no luck in finding one. I had seen one in the online catalogue of Albicalor in Albergaria a Velha near Aveiro, so the local builders merchants ended up getting it for me from them. Albicalor list 90-litre insulated and uninsulated, 150-litre insulated and 200-litre insulated. This wasn’t a cheap heater – it was a lot more than I thought it was going to be, almost double – and the builders merchants didn’t make a cent on it. After I bought it I found out that Centrotorneiras near Coimbra stocks them for around the price I thought they ought to be. I can’t link direct to the item on their site, but if you search for ‘bailarinas’ you’ll find them. The insulated one is currently €810. They also do an uninsulated 150-litre one for €560. You don’t want to know what I paid …

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