Many governments and regulators around the world have adopted The Precautionary Principle, adapting them to various elements of concern such as the use of water heaters as a heat source.

The Precautionary Principle

"The precautionary approach/principle is a distinctive approach to managing threats of serious or irreversible harm where there is scientific uncertainty.

The precautionary approach recognizes that the absence of full scientific certainty shall not be used as a reason to postpone decisions where there is a risk of serious or irreversible harm. Even though scientific information may be inconclusive, decisions have to be made to meet society's expectations that risks be addressed and living standards maintained."

Source: Environment Canada

In summary, the principle states:

If expected harm from an action or product is very substantial and

if the scientific forecasting of expected harm is fairly uncertain,

then measures to anticipate and prevent harm are justifiable.

Return to water heaters as boilers

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An excerpt from The Wingspread Statement on the Precautionary Principle, January 1998, as provided by the Science and Environmental Health Network is its simplest form, "When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."

A useful resource on the Precautionary Principle by the World Commission on the Ethics of Scientific Knowledge and Technology (COMEST), published by UNESCO can be found here.