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Non-Potable Water for Toilet Flushing

Posted by: Abram Richardson on Friday, June 16, 2017

5,000-gallon storage tank

As the thought of conserving water continues to increase more people are looking for ways to reduce the wasteful use of potable water. Over the past 25 years we have seen how effective the code-mandated low-flow faucets and showerheads as well as low flush rate toilets and urinals have been in reducing potable water consumption. An effective way to reduce the strain on potable water resources is by using alternative non-potable sources of water to flush toilets and urinals. Approved non-potable water sources may be used with the code mandated maximum flush rate fixtures or in conjunction with higher performing flush rate fixtures. Non-potable water sources which could be considered for flushing toilets and urinals may include the following:

  • Gray Water – Requirements are often included in many standard codes (i.e. Florida Building Code, 5th Edition - Plumbing)
  • Rain Water – May be restricted and/or prohibited in some states and local jurisdictions
  • Reclaim Water – May not be available by utility purveyor in some locations and where available it may be restricted and/or prohibited for use in toilet and urinal flushing


The three non-potable water sources mentioned above may not be approved or even regulated by codes in some states and/or local jurisdictions so it is imperative the design team work closely with building owners, the local water purveyor, Health Department and Building Officials to determine if an alternative non-potable water source can be used for toilet and urinal flushing on their proposed project.

Once guidelines are confirmed and/or provided with the local authorities the design team should work closely with the property owner to determine the non-potable water source, how the water will be collected, the location of the tank(s), pump(s), pump controls, water treatment equipment, if required and back-up water service. In areas with adequate rainfall there are various rainwater harvesting companies that offer many types and arrangements of tanks, cisterns, pumps as well as treatment options and some offer turnkey systems.

The use of non-potable water for toilet and urinal flushing may provide the property owner with an excellent opportunity to help reduce the demand on their local potable water resources. What a privilege it is to help conscious minded property owners and at the same time play a role in reducing the wasteful use of potable water.

In Florida many local Building Officials, Health Departments and Water Purveyors have allowed the use of rainwater collection for toilet flushing. Each jurisdiction may require various system requirements so always check with the state and local authorities.

Rainwater is collected from the roof of a building via surface mounted down spouts
with pre-filter fittings to fill two 5,000-gallon storage tanks.

Two 5,000-gallon storage tanks used to store rainwater collected from the
building roof with chlorine shot pump and tank and two cartridge filters.


Cistern tank pump, pump controllers and bladder tank.