It will generally be the building department that enforces plumbing code requirements about pipe sizes, materials, placement, etc. Tanks over a certain size may require a permit—5000 gal/ 18.9 m3 in our county. Large, constructed tanks may require a permit with an engineer’s stamp on the structural plans. Some of the tank-specific requirements we’ve heard of:
Lockable lid to guard against malicious contamination and drowning hazard
Sealing lid to guard against entry of roof runoff and creatures
Overflow with mosquito trap
Soil report for the structural soundness of the soil that supports the tank
The fire department may require that a hydrant be attached to the tank, with a certain-sized connection (4” in our area). They may require a “set-aside” or reserve of a specific size (2000 gal/ 9.5 m3 in our area) that can only be accessed via their hydrant—not a bad idea, if you want them to be able to save your house. This can be accomplished by putting the hydrant outlet at the bottom and the domestic supply outlet higher up.
The health department may have their own rules, or defer to the building department. The vector control department may want to ensure that your water storage does not breed mosquitoes.
Ideas for Really Cheap Storage
If economy is an overriding consideration, here are some suggestions for really cheap storage:
Salvage 30 or 55 gallon drums can often be scrounged for little or nothing. The bungs often have 3/4” pipe threads, facilitating attachment of inexpensive plumbing, for example small diameter polyethylene tubing. Drums can also be drilled, tapped, threaded, or fitted with bulkhead fittings to make inlets and outlets in any position.
Tote bins used for palletized, bulk transport of liquids. They can be made into passable small tanks, if they’ve contained something non-hazardous. They are usually 275 gal (1 m3) HDPE containers.
Above-ground swimming pools are the cheapest, funkiest storage going. Not a long-term solution, but you can’t beat the cost. The plastic walls are usually PVC.
Ponds can be relatively inexpensive for large volumes of water.
Aquifers usually don’t cost anything and can store vast amounts of water.
For More Information
For information on all types of water storage, worked examples of how to size water tanks, and extensive information on tank materials, see Water Storage, Oasis Design Press 2005. http://www.waterstorage.ws.