Residential home surveys target both indoor and outdoor water use. In practice, home surveys usually include a site visit by trained staff that: (1) solicits information on current water use practices; and (2) makes recommendations for improvements in those practices. Sometimes indoor plumbing retrofit devices are directly installed when appropriate. The outdoor portion of the survey can vary widely, ranging from an intensive outdoor water efficiency study (turf audit, catch can test, and written recommendations for irrigation scheduling or landscape changes) to simple provision of a brochure on outdoor watering practices.
BMP 1 – Residential Water Surveys.
BMP 2 – Residential Plumbing Retrofit. Residential surveys may involve plumbing retrofits.
BMP 6 – High Efficiency Washing Machines. Residential surveys may result in washing machine replacement.
BMP 10 – Wholesale Agency Assistance. Surveys are applicable to wholesale assistance and incentive programs.
BMP 14 – Residential ULFT. Residential surveys may result in ULFT replacement.
Available Water Savings Estimates
Summary of Individual Studies
The Contra Costa County Water District (CCWD) has offered residential surveys to its customers since 1988 and it has conducted at least two water savings evaluations. CCWD (2000) reports that savings in 1999 resulting from surveys conducted in 1998 were 42 to 55 gallons per day, with variation depending on survey approach. This study concluded that survey water savings depend on the particular auditor’s implementation and on the pre-program water consumption of the customer. Most of the savings were found in the spring and fall months. “Customer water use patterns are better correlated with maximum temperature than the more theoretically correct measure of ETo.”
CCWD (1994) reports evaluation results of a residential water audit evaluation designed to determine the water savings from a program that was implemented from 1989 to 1993. Of the 4,390 audits CCWD conducted, 2,216 were selected for the evaluation study because the customers: (1) had complete audits (indoor and outdoor), (2) had only one audit, and (3) stayed in the same home for the five-year study period. After statistically controlling for indoor and outdoor household characteristics, the study determined that audit savings were between 6 and 24 percent with an average of 16 percent. The study found that water savings were higher in the summer and that homes with irrigation timers used more water than homes without timers.
Two methods of estimating savings from residential home surveys are provided. The first estimates one total number for survey savings and the second estimates a number for each of the components of a survey. Both sets of figures are derived from statistical analyses of data collected in field studies. The second method allows design of the survey using different components.
Total Survey Savings Method
Savings from intensive home surveys targeted to high water users:
- 32.2 gpd per single-family household (weighted average of targeted survey savings reported in MWDSC 1994 and Chesnutt, McSpadden, and Pekelney 1995).
Savings from untargeted intensive home surveys:
- 21 gpd per household (1/3 the above amount, observed ratio in MWDSC 1994).
Survey Components Method
The savings estimates in Table 1 indicate the device savings from various survey components. One can estimate savings from different design surveys by choosing the component savings from the table. Method 1 accounts for savings decay by showing the average savings over a finite number of years representing the device life span. Method 2 provides an alternative, whereby the savings are reduced by the indicated percent over the period of analysis or until savings approach zero.
Table 1 - Component Savings
|Method 1||Method 2|
|Survey Component Device||Initial Savings (gpd per device)||Device Life Span||Device Decay Rate per Year|
|Low Flow Showerheads||5.5 gpd||3-7 years||20-30 percent|
|Toilet Displacement Devices||4 gpd||2-5 years||40-60 percent|
|Faucet Aerators||1.5 gpd||1-3 years||40-60 percent|
|Toilet Leak Detection||.64 gpd (8 gpd per repaired leaking toilet; 8 percent of toilets leak)||7-10 years||1-2 percent|
|Other Household Leak Check||.5 gpd (12.4 gpd per household repair; 4 percent of households with leaks)||7-10 years||1-2 percent|
|Turf Audit||12.2||4 years||40-60 percent|
|Turf Audit with Timer||25.9 gpd (12.2 gpd for turf audit plus 13.7 if timer)||4 years||40-60 percent|
The persistence of water savings is one of the central issues to estimating the cost-effectiveness of residential home surveys. This issue is rarely addressed in empirical impact evaluations because of the expense and intrinsic difficulty of providing a multiple-year measure of impact. One such example was based on data from a field study in Los Angeles (Chesnutt, McSpadden, and Pekelney 1995). Examining early participants and four years of post-intervention water use data, Figure 1 was developed.
Figure 1 plots the average annual net water savings for each year following the initial home survey. The net water savings held up surprisingly well during the first three years. The fourth year appears to give some evidence of a decline in water savings, but some caveats are in order. First, there is a greater amount of uncertainty surrounding the savings in the fourth year. This is due to the smaller sample size of Phase I participants that possessed four years of post-intervention water use. The broader bands of uncertainty surrounding the fourth year of water use make it more difficult to discern any decline in water savings. Second, the estimated level of water savings in the fourth year may also reflect characteristics of the smaller sample of early participants that does not reflect later participants. The authors caution against drawing too much inference about the magnitude of decay in water savings from this early evidence and recommend more long-term follow-up of conservation program results.
The CCWD study calculated water savings persistence in three time periods subsequent to audit implementation: “Savings over the first year, second year, and beyond average 17 percent, 16 percent, and 13 percent respectively” (CCWD 1994).
The persistence of water savings from residential surveys remains a difficult quantity to predict.
Confidence in Estimates
Program and Device/Activity Cost Estimates
Participant program costs may include:
- Cost of survey devices/materials if not fully subsidized
- Installation cost if not fully subsidized Supplier program costs may include:
- Staff time to develop survey materials, target sites, and conduct survey (if not contracted out)
- Survey equipment and devices
CCWD (1994) estimated their program costs as they were incurred in their 1993 CCWD program implementation (Table 2).
Table 2 - Cost of Residential Audit
|Toilet dam||1.54@ $1.20||1.85|
|Bucket (1993 only)||1.8|
|Milage||17 mi.@ $.28/mi.||4.76|
Reproduced from CCWD 1994.
The following are professional judgments of costs by conservation program coordinators and managers, as reported in MWDSC (1995):
- Survey, targeted indoor/outdoor: $200
- Survey, untargeted indoor: $40
- Low flow showerheads, kit: $2
- Moisture sensor, residential: $125
- Irrigation timer, residential: $230
- Swimming pool/spa covers: $5-150
- Low flow showerheads, direct install: $10-15
Plumbing retrofit costs are estimated in HUD (2002) as follows: “Device or material costs were obtained from large manufacturers/providers throughout the United States. Labor costs were assumed at $36 per hour for a laborer and $60 per hour for a technician or a plumber. The times required to complete the various tasks were approximated from literature on the subject and/or information from professionals in the field.” Additional estimated costs are listed in Table 3.
Table 3 – Estimated Costs of Implementation for Retrofit Strategies
|Install low-flow faucet aerators||$2.00|
|Install low-flow showerheads||$5-$17|
|Install toilet displacement devices||$1.00|
|Install quick-closing flappers in toilets||$14-$22|
|Adjust water level in toilets||$20-$32|
|Detect and repair toilet leaks||$11-29|
|Detect and repair faucet leaks||$6.00|
|Detect and repair showerhead leaks||$6-$10|
|Install free aerators, showerheads, toilet inserts||$12 installation cost per set for eachapartment unit|
Source: Reproduced plumbing retrofit costs from HUD (2002)
Costs vary with scale of the program and the weather—hot and dry periods make for easier marketing to many residential customers.
Confidence in Estimates
Achieved conservation from residential home water surveys can vary widely depending upon: (1) the content of the survey, (2) the targeted marketing, and (3) the water and wastewater rate structures in place.
Water Savings Calculation Formula(s)
Water Savings = Survey_Savings * Number_of_Surveys
Factors to Consider in Applying the Formula Survey savings can vary greatly depending on weather, water rates, and follow-up. Multiplying by “Number_of_Surveys” as shown above allows the calculation of program savings, not just from a single survey, assuming constant savings by scale. Survey_Savings is an average over the years of estimation, with decay imbedded.
Water Savings = Survey_Savings * Number_of_Surveys
11,000 gpd per 1000 Surveys = (5.5gpd + 4gpd + 1.5gpd) * 1000 Surveys
Questions to Ask
- Are there other agencies that you can develop partnerships with to make your program more cost effective?
- Does your agency have access to grant or other partnership type funding?
- Is the survey targeted, and to whom?
- What marketing technique(s) will be used to enlist customer participation and will the selected technique(s) include incentives?
- How many times are customers contacted?
- What are climatic conditions, and do you have the ETo for determining the right application of water?
- Are the landscape areas generally small or large, are most watered by hand or by automatic sprinkler system?
- Do you intend to conduct the surveys with agency personnel or contract out?
- Does your agency allow your personnel or contractor to enter the customer’s home?
- What are the elements of the survey (devices, actions, etc.)?
- Do you have estimated or comparative costs for survey/device components and method selected to implement the program?
- If you intend to provide devices (BMP 2) or ULFTs (BMP 14) with your survey program, will your personnel or the contractor install the devices and/or ULFTs. If not, how will installations be verified?
- How will you use the survey results and will results be tied to a customer specific database (customer conservation screen)?
- Are you going to design and maintain a database covering all participants and program results?
Can you influence how the cost of this program is accounted for? If capitalized, the cost impact will be spread over “x” number of years and reduce the rate impact. If expensed, will the cost of your program have to be recovered in one year?
CCWD (1994), “Residential Water Audit Evaluation,” prepared for Contra Costa Water District by John B. Whitcomb, Ph.D., August.
CCWD (2000), “Residential Water Survey Evaluation,” prepared for Contra Costa Water District by John B. Whitcomb, Ph.D., May. Chesnutt, T., C. McSpadden, and D. Pekelney (1995), “What is the Reliable Yield from Residential Home Water Survey Programs?” presented at the AWWA Conference in Anaheim CA, June.
HUD (2002), “Retrofitting Apartment Buildings to Conserve Water,” prepared for U.S. Department of Housing and Urban Development by Water Resources Engineering Inc., May.
MWDSC (1994), “Residential Water Audit Program: Evaluation of Program Outcomes and Water Savings,” prepared for Metropolitan Water District of Southern California by A&N Technical Services, Inc., December.
MWDSC (1995), “Reference Document: Program Design Tool and Savings Estimates,” prepared for Metropolitan Water District of Southern California by A&N Technical Services, Inc.
|Has general subject||Benefits and costs +|
|Has introduction||Residential home surveys target both indoo … |
Residential home surveys target both indoor and outdoor water use. In practice, home surveys usually include a site visit by trained staff that: (1) solicits information on current water use practices; and (2) makes recommendations for improvements in those practices. Sometimes indoor plumbing retrofit devices are directly installed when appropriate. The outdoor portion of the survey can vary widely, ranging from an intensive outdoor water efficiency study (turf audit, catch can test, and written recommendations for irrigation scheduling or landscape changes) to simple provision of a brochure on outdoor watering practices.a brochure on outdoor watering practices. +