Date of Award

Spring 2009

Document Type



Mathematics, Engineering & Computer Science

First Advisor

Gary Fischer

Second Advisor

John Scharf

Third Advisor

Murphy Fox


The semi-arid western United States views water as a valuable commodity. Because of water’s expense and difficulty to obtain, western states struggle with water supply, use, and rights issues. The existing supply may not support an increasing population. Since the battle for freshwater is on-going, a special conservation method is being used by some states. Four different states have adopted laws allowing gray water irrigation, and as a result have been able to mitigate some of their water issues. Montana is now exploring this possibility. In April 2007, the state legislature passed a bill permitting the regulated use of gray water. From the resulting statute, the Montana Department of Environmental Quality (DEQ) has been designated to develop, adopt, administer, and enforce administrative rules for gray water use. The rules are currently under review pending their final approval. Under these rules, each household can use at least forty gallons of gray water per person per day during the months April through October. While this is a positive step in water conservation, the economic feasibility needs to be determined. This study investigates the financial costs and/or savings that could result from implementing a gray water system for a residential use in Lewistown, Montana. This document shows findings from efforts to measure gray water volumes and to obtain cost estimates for home water system modifications. The intent of this study is to provide baseline information pertaining to the feasibility of gray water use in a Montana residence.