Plumbing Technical Detail

I have been asked to show a bit more of the technical aspects of the van plumbing by a fellow DIY'er to show clearly how the system works. Here is the master plumbing diagram:

As a step by step guide, here's how it works.

Rainfall is collected by the gutter running around the perimeter of the roof. This rainwater is fed into an open cell Polyethelene Foam protected slow sand filter. This provides biological filtering as well as sediment and particulate filtering to the raw rainwater. What comes out of this filter is 'clearwater' which is then stored in a 120 litre plastic tank. This tank has an overflow pipe (not shown) to allow excess water to run out of the system. After the storage tank, the water is split two ways. One path flows through the IX600 reverse osmosis and carbon filter rendering the water almost 100 pure and pretty much potable. This cold supply is fed to the cold tap in the kitchen and is used to provide the drinking water for coffee, etc. The flow rate isn't great as the IX 600 filter is fairly restrictive off mains pressure (I only have about 0.9m of static head at best), but it is more than enough for potable purposes.

The second path from the storage tank is used to fill the calorifier cylinder at the lower end. This calorifier is an electric undersink 5 litre water heater that has had the immersion heater element removed and a heat exchanger copper coil fitted. The hot water generated by the solar collector is pumped through this coil, allowing the water stored in the 5 litre stainless steel tank to take up the heat produced. Hot water then exits the top of the calorifier when the hot tap is used in the kitchenette. The flow is better than the cold as it has no restrictive filtering inline.

Unlike a conventional domestic HW system, the header tank for the solar is not fed from a mains supply to allow for evaporation or seepage in the system. With a maximum primary circuit volume of around 6 litres, an automatic top-up of the solar circuit was not deemed necessary. Likewise, a separate feed and expansion (with vent pipe) was not required as any air is purged from the system when it is first filled and the excess water in the header tank is purely to allow the total volume of the water in the primary circuit to increase or decrease as a function of temperature.

For simplicity, I have also omitted such items as the Y-strainer and isolator valve in the flow from the panel, draindown valve at the lowest point in the system and the isolators for the hot and cold water systems.