1. Toilet Saturation Study
Fall 2015
Low-Flow Toilet Saturation Study
Solano County Water Agency
Fall 2015
City: Fairfield, California
Objective: Using a random sample, find the most current estimated saturation of low-flow toilets (1.6
gallons per flush [gpf] or less) in pre-1993 single-family homes in the City of Fairfield. This data will be
compared to findings from the most recent time this study was done in 2008.
Similarly, also find the estimated saturation of low-flow toilets in pre-1993 apartment
complexes.
Single-Family Homes
Method:
 Preparation
 Locate or purchase database of pre-1993 single-family homes in city to be studied
o In Fairfield: We used a database of homes that were built before 1993
 Total number of the population was 20,604 homes (49,450 toilets)
 Generate random sample to be studied
o In Fairfield: Data was recorded from a total of 92 homes
 Statistical parameters:
 20,604 homes
 95% confidence level
 10 confidence interval which generated a sample size of 92
 *Optional: Send letter to residents to notify them of the study; the letter also includes
instructions so residents can find the toilet date/gpf and call the data in
 Input addresses into map customizer website, which generates points on the map
 Divide map into sections of 5-10 points each, using screenshots
 Prepare binder: hard-copy of tracking form, maps, pens, conservation information
 Execution
 Choose section and use GPS to drive around in pairs and visit pre-selected addresses
 Can visit section local to home water-surveys, or any location when not busy
 If no one answers at predetermined address, continue cold-knocking on neighboring houses
on same street (record new address in such cases)
 Upon knocking: State what organization you are from, why you are doing the study, and ask
the two questions:
1. How many toilets are in the home?
2. What year they were installed?
 If homeowner is unaware of the year, ask them to look under the lid or in the tank of
the toilet, or offer to do it yourself - show photos of where the date/year can be
located (examples in the study binder)
 Record findings and cross off point on map
 Post-Data Collection
 Input findings into database (excel) with pre-set formulas upon return to office
Time: Study was completed over about a month-long period but could easily be shortened, schedules
permitting. Depending on resident response and travel time, each map section takes 1-3 hours to
complete. There are about 10 map sections depending on sample size.

2. Toilet Saturation Study
Fall 2015
↑ ~62% of total toilets surveyed were
low-flow. This is only up 3% from when
the study was last done in 2008.
2008: 59% low-flow saturation
← 75% of total houses
surveyed had at least 1
low-flow toilet.
Findings (from Excel spreadsheet):
Total High-Flow 79
Total Low-Flow 128
Saturation of Low Flow
Toilets 0.6184
Study Conflicts:
 Heavy pushback from home renters - much less likely to be willing to check date or let us check
 Some addresses were in gated communities/ had gated driveways, therefore could not be entered
 “No Soliciting” signs common, plus other more aggressive, even threatening signage that
prevented us from visiting homes
 Some locations from the sample turned out not to be single-family homes
Comments:
 Letter to residents was only a minor help. 2 of ~80 people called data in, and ~4 had the
information ready for us/seemed prepared for us upon arrival
 Residents seemed more willing to assist with the study if we presented ourselves as “City of
Fairfield Water Conservation” rather than “Solano County Water Agency”
 Good opportunity to look for water waste while out driving around
 Spanish language would be a big barrier without Spanish-speaking intern
 Many residents who had not replaced any toilets were seniors
 Some residents who had very recently replaced their toilets were unaware of state rebates
Conclusion:
 Only ~3% increase in low-flow toilet saturation over 7-year period (2008-2015)
o At that rate, it would take ~90 years to reach 100% low-flow toilet saturation, by which
time most if not all homes will likely have been rebuilt
 If possible, may be useful to request funding for direct-install program, which would be helpful
for seniors and people with disabilities
 If Solano County or cities do not provide toilet rebates, stronger marketing of state rebates would
be advised in order to increase saturation
Sample of map with inputted addresses:
Households
With NO Low-
Flow 23
Households
With 1+ Low-
Flow 69
Saturation of
Households
w/1+ Low-Flow 0.75
Households
with ALL
Low-Flow 0.4674
← ~47% of households surveyed
had replaced 100% of their toilets
with low-flow models.

3. Toilet Saturation Study
Fall 2015
Apartment Complexes
Method:
 Preparation:
 Locate or purchase database of pre-1993 apartment complexes in city to be studied (our
database already had contacted numbers associated with addresses)
 In Fairfield: 13 addresses turned out to be apartments built pre-1993
 Execution:
 Call each complex, asking for total # of toilets and total # replaced since 1993
 Post-Data Collection
 Record data in Excel spreadsheet for apartments
Study Conflicts:
 4 of 13 complexes surveyed did not have records of how many total toilets had been replaced;
only replaced toilets as needed and did not have a cumulative record available
 Multiple addresses in database were complexes built after 1993
 Some did not know how many total toilets they had
 This is the first time this study has been done with apartment complexes, so there is no data to
compare it to
Comments:
 Due to study conflicts, confidence level for estimated saturation of low-flow toilets in
pre-1993 apartment complexes is much lower than it is for pre-1993 single-family homes
 With this in mind, study finds that ~60% of toilets in pre-1993 apartment
complexes are low-flow