The lowest cost soil for earth building comes from the building site itself. Dig the soil onsite and you could build a ferrocement tank below ground in the pit. You could build a low cost roof over the top and use gutters to direct water into the pit to store large amounts of water. Seal the tank and it could be used for drinking water. If left open to the atmosphere, the water would be non-potable since it would attract insects and algae would grow.
More information at the source: Jalvardhini.org
Note how these storage tanks could store all sorts of things besides water.
4 thoughts on “Below Ground Ferrocement Rainwater Tank”
An FC vault would be good, with a moveable formwork, like the cardboard formwork we saw a few weeks ago.
If the span wasn’t too great (16ft or less), you could do Latex Concret with a PVC frame, like a “hoophouse” for gardening. PVC frame, then billboard tarp for form, shadecloth for mesh, and paint a few layers of latex/concrete. Done. It’s not the cheapest option, but would be comparable with FC, and a lot faster.
You could slope the property,use small gully’s to run off into this also.
For most climates that need water storage, a roof is essential, not just for keeping the water clean, but to prevent evaporation. I’ve seen open tanks dry up within a few months in the Chihuahuan desert.
With a simple arch form, you could do a ferrocement roof on this tank. Alternatively, do a Latex concrete roof, like we do on our rain catchment tanks: http://velacreations.com/water/water-storage/item/313-cistern-howto.html
Good idea about vaulted ferrocement cisterns. This design would be very practical. I haven’t found any pictures yet.