09-19-2010, 07:02 PM
Does anyone know what the code says about what you can build on top of a catchment tank? I know the plumbing code says that sewage and water piping in a ditch have to be separated by so much horizontal and vertical distance so it makes sense that you should not build the toilet on top of the catchment tank. Clearly you can have bedrooms and lanais on top of catchment tanks, since Peter and John the Architect have both done so. Somewhere it must say exactly what is permitted. What I am thinking is having a large tank under the center of the house but with toilet and kitchen plumbing around the perimeter so it is not over the tank. Is a floor level change required such that the potentially floodable floors are lower than the top of the tank? This is where the exact wording of the code comes in.
I have also considered having a couple of long slender tanks on either side of the house, outside the footprint of the living areas proper but forming the lanais. Perhaps I am getting hung up on symmetry but I also want to take advantage of what I assume will be the very strong construction of the concrete tank and make it do double duty as a very strong foundation for the house. Granted this is usually for large buildings but there is something called a cellular raft foundation with top and bottom slabs and vertical walls between forming a sort of rigid egg crate. So in effect the slab is several feet thick but "hollow" and partitioned into several rectangular or cubical volumes. Sounds like ready made cisterns to me. The same effect is what gives corrugated cardboard its rigidity compared to single layers of paper. Since the walls separating the individual compartments are shear walls and are there for strength, openings between compartments must be small and well reinforced. This would not work for an underground parking garage where you can only tolerate isolated columns here and there but seems perfectly suited for using some of these spaces as watertight tanks. Back to the code. What parts can be tanks and what must remain crawlspaces, or utility rooms depending on how tall this whole affair is? Logic would say lanais, bedrooms, living rooms, and dining rooms could be built on top of tanks while anything with waste piping could not.
I have also considered having a couple of long slender tanks on either side of the house, outside the footprint of the living areas proper but forming the lanais. Perhaps I am getting hung up on symmetry but I also want to take advantage of what I assume will be the very strong construction of the concrete tank and make it do double duty as a very strong foundation for the house. Granted this is usually for large buildings but there is something called a cellular raft foundation with top and bottom slabs and vertical walls between forming a sort of rigid egg crate. So in effect the slab is several feet thick but "hollow" and partitioned into several rectangular or cubical volumes. Sounds like ready made cisterns to me. The same effect is what gives corrugated cardboard its rigidity compared to single layers of paper. Since the walls separating the individual compartments are shear walls and are there for strength, openings between compartments must be small and well reinforced. This would not work for an underground parking garage where you can only tolerate isolated columns here and there but seems perfectly suited for using some of these spaces as watertight tanks. Back to the code. What parts can be tanks and what must remain crawlspaces, or utility rooms depending on how tall this whole affair is? Logic would say lanais, bedrooms, living rooms, and dining rooms could be built on top of tanks while anything with waste piping could not.