Using Gray Water
Gray water is not as clean as rainwater, or even as clean as stormwater. We can expect a steady flow of suspended and dissolved organic material, plus the byproducts of the cleaning chemicals. However, the water is safe for many uses. The simplest is turf irrigation. Most plumbing codes do not require treatment of gray water, when used for irrigation, provided that the water is used within 48 hours. This can be accomplished automatically, using an irrigation controller. While this does provide irrigation water, it is not the most efficient use of the available water. We must irrigate whether the lawn needs it or not, in order to meet the requirements of the plumbing code (and not allow the water to go septic and stink. Nobody wants a smelly lawn).
Gray water treatment is more challenging than rainwater, due to both the continuous stream of sediment and the presence of cleaning agents. Many gray water treatment systems require continuous monitoring or adjustment, or have been abandoned due to these requirements. To this end NSF created Standard 350, that verifies performance AND ease of operation. For more about the NSF 350 standard, click here.