Pre-Rinse Spray Valves

Commercial pre-rinse spray valves (PRSV) are handheld spraying devices with a normally-closed valve that can be squeezed open by pressing a lever. Pre-rinsing involves manual spraying with hot water under pressure to remove loose or sticky food residue from food service items, such as, plates, dishes, utensils, and so on, before final cleaning in a commercial-grade dishwasher. PRSVs are often marketed along with dishwashers designed for commercial and institutional use (in very small scale commercial settings the entire cleaning process may be performed by a PRSV with no dishwasher present). Since PRSVs use a lot of water (usually more than the dishwasher), that too hot water, improved efficiency in this end use has received considerable attention from both energy and water utilities that have often partnered to implement direct-install PRSV retrofit programs[1]. PRSV design, however, must balance minimized water and energy use with its ability to remove food residue. Failure to meet the latter goal only increases pre-rinse times (or rejection of new equipment altogether), which in turn lessens achieved water and energy savings.

HISTORY OF CODES AND REGULATIONS

California water suppliers first attempted to improve PRSV efficiency under the auspices of CUWCC’s Pre-Rinse Spray Head Distribution Program in 2002.[1] PRSVs in the past used over 3 gallons per minute (gpm) on average, with some models using over 5 gpm. Working in concert with the Food Service Technology Center (FSTC), which undertook laboratory testing of PRSVs available in the market back in the early 2000s, PRSVs with flow rates under 1.6 gpm but a different spray pattern (knife-like) were found to be as effective as non-efficient PRSVs (with a showerhead-like spray pattern). Effectiveness was measured in terms of time required to rinse tomato paste off of a plate (“cleanability”). This lower flow rate of 1.6 gpm then became the standard that was used by CUWCC to promote efficient PRSVs through rebate programs, but non-efficient PRSVs still remained available for sale in California.

The availability of PRSVs became restricted nationwide to models that use no more than 1.6 gpm when federal efficiency standards were extended to commercial pre-rinse spray valves by the Department of Energy (DOE) via the Energy Policy Act of 2005 (EPAct 2005), coming into force on January 1, 2006.[2] The federal standard included in EPAct 2005 does not include a test for performance, however, just efficiency; this is expected to change in the near future. The DOE has not waived federal preemption of state law in the case of PRSV efficiency standards, so California’s Appliance Efficiency Standards (Title 20 of the California Code of Regulations)[3] have to remain consistent with federal law, which means that PRSVs using up to 1.6 gpm can be sold or offered for sale in California. However, California’s Title 20 regulations for PRSVs do include a performance component (a PRSV must be able to remove food residue from 60 plates in 30 seconds a plate or less, on average; the “cleanability” test originally developed by the FSTC). The California Plumbing Code and the Green Building Code (Title 24 of the California Code of Regulations) are consistent with the federal standard in terms of efficiency. However, since it is Title 20 regulations that control what can be offered for sale in California, PRSVs installed in buildings subject to the Plumbing Code or Green Building Code also become subject to California’s performance standard.

Several organizations have attempted to promote greater PRSV efficiency through voluntary certification programs. For example, the Environmental Protection Agency (EPA) has undertaken a voluntary labeling and certification program, WaterSense, analogous to the EnergyStar program, to promote water use efficiency in the US. A WaterSense specification for PRSVs was adopted in 2013, which lowered the maximum permissible flow rate to 1.28 gpm,[4] and also includes tests for PRSV performance and longevity based on EPA’s field research. According to this research, “spray force” is a more objective and reliable indicator of user satisfaction than California’s “cleanability” performance metric.[5] WaterSense compliant PRSVs must be able to deliver a “spray force” exceeding 4 ounces during laboratory testing. The DOE has already initiated rulemaking procedures to incorporate this “spray force” performance metric into the mandatory federal standard for PRSVs. Once this is approved, the California Energy Commission will likely follow suit by substituting the “spray force” performance standard in place of the existing “cleanability” standard in its Title 20 regulations.


Table 1 Various Standards Influencing Sale or Installation of PRSVs in California

Mandatory or Voluntary Standard Efficiency and Performance Standard Effective Date
Federal Standard (mandatory) <=1.6 gpm at 60 psi; no performance standard 01/01/06
California Title 20 Standard (mandatory) <=1.6 gpm at 60 psi; "cleanability" performance standard 01/01/06
WaterSense Standard (voluntary) <=1.28 gpm at 60 psi; "spray force" performance standard; also includes life cycle testing standard 09/19/13
Food Service Technology Center (voluntary) <=1.15 gpm at 60 psi; "cleanability" performance standard Fall 2014


Table 1 summarizes PRSV standards in California. The FSTC’s recommendation is also shown because they have been an important player in improving water and energy use efficiency in commercial kitchens.[6] FSTC recently modified its recommendation and limits rebates to PRSV models that use under 1.15 gpm. As mentioned earlier, most existing standards that rely on “cleanability” to judge performance will more than likely switch to the “spray force” performance metric once DOE includes this criterion in the mandatory federal standard. The Alliance for Water Efficiency’s website offers additional valuable resources about the evolution of codes and standards over time.

PRSVs using as little as 0.65 gpm are now available for food service applications. Performance of these ultra-low-flow PRSVs, however, is quite sensitive to inlet water pressure (more on this later).

WATER SAVINGS

Several studies have evaluated water and energy savings, and user satisfaction, associated with efficient PRSVs (Table 2). Only the subject of water savings is highlighted here. All these studies have estimated PRSV savings by physically metering water usage, before and after a retrofit. Except for the CUWCC Phase 2 evaluation, they all suggest that PRSVs save a significant amount of water and energy, so much so that the cost of a retrofit pays for itself within a year or less, on average. For this reason, many utilities (often energy and water utilities in partnership) run direct install programs at no cost to the program participant. The cost-effectiveness of PRSV retrofits is, therefore, largely a settled question. What is less settled is figuring out how to use results from the existing studies to estimate savings from future PRSV retrofit programs where conditions may be different from what was evaluated by aforementioned studies?

Field studies have identified several drivers of water savings, mostly self-evident, such as the flow rate difference between the existing and replacement PRSVs, length of time per day in use (and whether this changes after switching to an efficient PRSV), inlet water pressure, and retention rate (dependent on user satisfaction). Additional drivers of energy savings include inlet cold water temperature and output spray water temperature desired by the PRSV operator. All of these factors likely vary across service areas.

A key driver of savings is obviously the difference between the flow rate of existing PRSVs and what they are replaced with. Data in Table 2 show that both can fluctuate considerably across field studies. Not surprisingly, earlier studies generally indicate a higher pre-retrofit average flow rate (except for the CUWCC Phase 2 evaluation that stands apart on this and other key metrics). Once the 1.6 gpm federal standard for PRSVs went into effect in 2006, natural turnover alone would be expected to improve efficiency. Therefore, taking the average of pre-retrofit flow rates across existing studies to estimate savings from a future program would not be a sensible strategy. Water suppliers would be better off performing field measurements in their service area to estimate this parameter. A similar recommendation applies for estimating post-retrofit flow rates.


Table 2 Key Savings Parameters from PRSV Evaluations

Study & Fieldwork Year Measured Flow Rate (gpm) Site Pressure (psi) Measured Usage (hours/day) Rated Flow Rates of Replacement PRSVs Estimated Savings per PRSV Retrofit (gpd)
Pre-Retrofit Post-Retrofit Pre-Retrofit Post-Retrofit
CUWCC Phase 1, 2002-03 3.35 1.11 61 n.a. 1.27 1.6 gpm1 171
CUWCC Phase 2, 2004-05 2.23 1.12 n.a. 0.543 0.733 1.6 gpm1 23
Waterloo, Canada, 2004 2.75 1.22 66 0.65 0.77 1.6 gpm1 51
Calgary, Canada, 2005 3.62 1.48 81 0.78 0.83 1.6 gpm1 96
WaterSense, 20104 2.32 0.89 62 1.29 1.32 <1.0 gpm1 108
“ " 1.32 68 " 1.5 1.0-1.24 gpm2 61
“ " 1.33 65 " 1.42 1.25-1.6 gpm2 67
SoCal. Gas Company, 2013 1.61 0.91 63 1.3 1.63 0.65-1.15 gpm2 37
Santa Cruz, CA, 2014 2.15 0.96 78 n.a. n.a. 0.65-1.15 gpm2 Santa Cruz, CA, 2014

NOTES:
1 Flow rated at 80 psi.
2 Flow rated at 60 psi.
3 Usage times exclude grocery stores, which are minimal users of PRSVs, but were included accidentally in the CUWCC Phase 2 study.
4 This study tried three different PRSVs of varying efficiency at each of the 10 test sites, which is why there are three sets of post-retrofit results.


Measuring PRSV flow rates and site pressure at each participating food service establishment before the retrofit, and from a random sub-sample of participants after the retrofit, need not be very expensive; collection of these metrics may need to become standard practice for implementing these programs in the future anyway. The reason for this is that the latest generation PRSVs (ultra-low-flow PRSVs using less than 1.0 gpm) are much more sensitive to inlet water pressure. The latest field studies (Table 2) that have experimented with ultra-low-flow PRSVs (WaterSense, Southern California Gas Company, and the City of Santa Cruz) have all shown that if these types of PRSVs are used at pressures much below 60 psi (laboratory test pressure), the risk of user dissatisfaction increases greatly. FSTC also recommends using PRSVs between the 1.0-1.15 gpm range if inlet pressure is too variable or too low. Assuming that a supplier allocates PRSVs based on site pressure, and that the distribution of pressures is similar to what was encountered in the Southern California Gas Company or City of Santa Cruz studies, suggests that a post–retrofit flow rate assumption between 0.9-1.0 gpm may be reasonable (depending on average inlet pressure). But, as stated earlier, field verification would be preferable. WaterSense discovered several PRSVs in their field study (EPA WaterSense, 2011, op cit.) that were operating at significantly higher flow rates than their rated flow rates.

Measuring average usage time is a significantly more complicated task than measuring flow rates, because it requires installing submeters. We have known since the CUWCC Phase 1 study that usage time measured in the field is much lower than what planners originally anticipated, and that actual metered usage hours is poorly correlated with self-reported usage hours (SBW Consulting Inc., 2004, op cit.). So, just asking food service establishments about their PRSV use is not a viable strategy for estimating usage time. Table 2’s data can offer some guidance on this issue. Ignoring the CUWCC Phase 1 and 2 studies (the former because it does not report pre-retrofit usage time, the latter because its key results set it apart from all the other studies), it appears PRSVs are used about 1 hour per day, on average; and that usage time increases by roughly 13%, on average, after switching to an efficient PRSV. In the absence of field data, we recommend water suppliers use both of these parameters for projecting savings from their PRSV retrofit programs.[7]

The final issue that savings calculations have to deal with is the issue of retention. The CUWCC Phase 1 and 2 evaluations examined this issue and found that retention was not a problem. Only about 5% of efficient PRSVs had been removed after 1 year from retrofit. Data about retention over a longer time period are not available. However, going forward, now that ultra-low-flow PRSVs have become available, this issue deserves greater scrutiny. Retrofit programs that fail to evaluate inlet water pressure may end up recommending ultra-low-flow PRSVs to those food service establishments for whom it may not be suitable, causing user dissatisfaction and subsequent equipment removal.

Table 2’s last column shows estimated savings per PRSV retrofit that prior evaluations have yielded. These estimates are computed from flowrate and usage time data shown in Table 2’s earlier columns, assuming a 100% retention rate.

How might a water supplier project savings from their PRSV retrofit program using results from existing field studies? The Santa Cruz field study is a good way to illustrate a potential methodology because this field study measured pre- and post-retrofit flow rates, but not usage times. Pre- and post-retrofit water use could be calculated as follows:

Pre-Retrofit Water Use per PRSV = (2.15 gallons per minute) x (60 minutes per day of average use)
Post-Ret\rofit Water Use per PRSV = (0.96 gallons per minute) x (60 minutes per day of average use) x (1.13 to account for 13% usage time increase at lower flow rates)
Net Water Savings = 64 gallons per PRSV retrofit per day

A further down-correction could be applied to the 64 gpd estimate to account for less than 100% retention over time.

COSTS

The FSTC has tested and recommends several PRSV models on their website. We searched for internet retail prices for as many of these models as we could find. In general, there appears to be a negative correlation between price and flow rate, but the correlation is weak. That means within each efficiency band (<1.0 gpm, 1.0-1.28 gpm, >1.28 gpm) a wide variety of PRSVs are available. The median retail price within each efficiency band works out to roughly $70-80, although it is possible to find models as cheap as $35 and as expensive as $110 (excluding taxes and shipping). The price variation reflects differences in features, ergonomics, materials and performance (over and above efficiency), which may influence retention. Water suppliers that purchase in bulk for a direct install program would be able to do better than the above estimates suggest.

DEVICE LIFE

Many of the published studies that have performed cost-effectiveness analyses use an average device life of 5 years (implying a natural turnover rate of 20%) for PRSVs. The basis for this estimate appears to be largely anecdotal, however, so merits improvement through additional field research.

THE CHALLENGE AHEAD

Although a high natural turnover rate is causing the installed stock of PRSVs to become more efficient over time, we expect these retrofit programs to remain cost-effective because of the steep increases in water and energy rates over the past few years.

A key issue that may be emerging, that did not exist before, is the need for better program targeting. Earlier, one could promote a 1.6 gpm PRSV with greater confidence across many different kinds of food service establishments. With the advent of ultra-low-flow PRSV designs, greater care is required in choosing an efficiency level appropriate for a particular kind of food service establishment, which implies that measurement of water pressure will need to become an integral component of PRSV retrofit programs. Otherwise, program savings may be compromised due to customer dissatisfaction. Additional field research is required to develop these water pressure based allocation rules so as to assure high retention rates.

Annotated Water Savings Literature

Although other entities outside of California are beginning to implement pre-rinse spray valve replacement programs, the acknowledged pioneer in such an undertaking is the CUWCC[8].

As such, the documentation of water savings associated with valve replacements has progressed beyond the “estimate” stage. In 2003, the CUWCC commissioned SBW Consulting Inc., Bellevue WA, to measure and evaluate the effectiveness of actual pre-rinse spray valve installations through the Program. By the end of Phase 1 of the CUWCC Program, 19 such field measurement projects had been completed. These served as a basis for the water savings estimates for the Phase 1 Program and are further described below.

The measurement of water consumption consisted of individually metering water use by each pre-rinse spray valve for 30 days both before and after retrofit. Additionally, water temperatures were measured and hours of actual spray valve use determined. Finally, flow rates of the old inefficient valves and the new efficient valves were measured by the FSTC at various water pressure levels.

Appendix A depicts the flow rate variability across a spectrum of flowing water pressures for three different (typical) valves. As can be seen in the figure, the difference in flow rates between the inefficient and efficient valves remains relatively constant from 30 to 60 pounds per square inch of water pressure. Thus, the water savings to be achieved through valve replacement at any given establishment can be assumed to be nearly the same regardless of the establishment’s line pressure.

Some water agencies outside of California have chosen to set their efficiency standard at 1.8-gpm rather than the 1.6-gpm called for in the standard in order to qualify more valves for their particular programs[9].

Water and energy savings per valve measured at the 19 metered sites[10] and extrapolated to the universe of installations under the CUWCC Phase 1 Program[11]. The majority of restaurants used water heated with gas, although a significant portion of California installations use electric water heating. Phase 1 Program results were as follows:


Water Savings
CCF[12]/year Gallons/year Acre-Feet/year
66.4 50000 0.153
Energy Savings – method of water heating
Natural Gas Electricity
335 therms/year 7,634 kWh/year

It must be noted that the above water and energy savings estimates are based predominantly upon field measurements within small establishments[13]. It is very likely that future outreach into food service chains and larger volume establishments will yield savings estimates that are much higher, due to the more intense use of the pre-rinse spray valve in the restaurant dish room. For example, prior to start-up of the CUWCC Phase 1 Program[14], laboratory estimates indicated that water savings across all types of food service establishments would average approximately 73,000 gallons per year. This figure was never achieved due to the customer restrictions placed upon the Program10. As such, documented savings data for the higher volume installations is not available.


Related Literature

File:Pre-Rinse Spary Valves for the Food Service Industry-PBMP-2004.pdf

SBW Consulting, Inc., Evaluation, Measurement and Verification Report for the CUWCC Pre-Rinse Spray Head Distribution Program, a report prepared for the California Urban Water Conservation Council, 2004.

SBW Consulting, Inc., Impact and Process Evaluation Final Report for California Urban Water Conservation Council 2004-05 Pre-Rinse Spray Valve Installation Program (Phase 2), a report prepared for the California Urban Water Conservation Council, 2007.

Gauley, B., Region of Waterloo: Pre-Rinse Spray Valve Pilot Study, a report prepared by Veritec Consulting Inc. for the Regional Municipality of Waterloo, Canada, 2005.

Gauley, B., City of Calgary: Pre-Rinse Spray Valve Pilot Study, a report prepared by Veritec Consulting Inc. for the City of Calgary Waterworks and Wastewater, Canada, 2005.

US Environmental Protection Agency (WaterSense), Pre-Rinse Spray Valves Field Study Report, March 31, 2011.

Valmiki, M.M. & M. Esser, Low Flow Pre-Rinse Sprayer Field Testing, a report prepared by NegaWatt Consulting for the Southern California Gas Company, 2013.

Liske, K. & L. Sotomayor, 2014 Pre-Rinse Spray Valve Direct Installation Program: Final Report, a report prepared by Ecology Action for the City of Santa Cruz Water Department, 2015.

Program Information

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Areas for Future Research

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Footnotes

  1. SBW Consulting, Inc., Evaluation, Measurement and Verification Report for the CUWCC Pre-Rinse Spray Head Distribution Program, a report prepared for the California Urban Water Conservation Council, 2004. SBW Consulting, Inc., Impact and Process Evaluation Final Report for California Urban Water Conservation Council 2004-05 Pre-Rinse Spray Valve Installation Program (Phase 2), a report prepared for the California Urban Water Conservation Council, 2007. Tso, B. & J. Koeller, Pre-Rinse Spray Valve Programs: How are They Really Doing?, 2005.
  2. Details about federal PRSV standards can be found here: https://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/54
  3. California Code of Regulations can be found here: www.oal.ca.gov
  4. www.epa.gov/watersense
  5. US Environmental Protection Agency (WaterSense), Pre-Rinse Spray Valves Field Study Report, March 31, 2011.
  6. .Additional details about PRSVs certified by FSTC can be found here: www.fishnick.com/equipment/sprayvalves
  7. Additional useful data that could help water suppliers develop water savings projections can be found in the following document: US Environmental Protection Agency (WaterSense), WaterSense Specification Pre-Rinse Spray Valves Supporting Statement, September 19, 2013.
  8. The Phase 1 Program was implemented by the CUWCC in 2002 and 2003; 16,903 existing pre-rinse spray valves in hot water applications were replaced in California; that Program was funded by (1) the California Public Utilities Commission (CPUC) with funds from the public goods charge levied on natural gas customers and (2) participating water providers. The existing Program consists of direct installation of the efficient valve in all applications where hot water is used (with certain limitations imposed by the CPUC). The inefficient valve is removed from the premises of the establishment so that it cannot be re-installed by the operator.
  9. Personal communication, Al Dietemann, Seattle Public Utilities.
  10. Other than an Applebee’s Restaurant, all of the other sites were small individually owned restaurants.
  11. SBW Consulting, 2004. Evaluation, Measurement & Verification Report for the CUWCC Pre-Rinse Spray Head Distribution Program. May 2, 2004
  12. CCF: hundred utilities.
  13. Due to conditions imposed by the California Public Utilities Commission (CPUC), the Council’s Phase 1 Pre-Rinse Spray Valve Program was focused primarily upon very small, small and “hard-to-reach” customers of the Investor Owned Utilities.
  14. Due to conditions imposed by the California Public Utilities Commission (CPUC), the Council’s Phase 1 Pre-Rinse Spray Valve Program was focused primarily upon very small, small and “hard-to-reach” customers of the Investor Owned Utilities.
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  1. Additional details can be found here: http://www.allianceforwaterefficiency.org/1Column.aspx?id=992&LangType=1033&terms=pre-rinse+spray+valves.