DRAFT B4 (10Mar17) ASSE International. Listing Evaluation Criteria for Shower Filtration Fitting for Reduction of Chloramine

Transcription

1 ASSE LEC # x ASSE Board Approved: ASSE International Listing Evaluation Criteria for Shower Filtration Fitting for Reduction of Chloramine DRAFT B4 (10Mar17)

2 General Information Neither this document, nor any portion thereof, may be reproduced without the written consent of ASSE International. No product may be said to be ASSE approved unless the manufacturer has applied to the ASSE, has had his product tested according to the applicable ASSE standards or listing evaluation criteria, and when the product has passed the test, displays the ASSE Seal on the product. Instructions for receiving the authorization to display the Seal are available from ASSE's International Office. Organizations wishing to adopt or list to any ASSE standard or listing evaluation criteria should print the ASSE number on the cover page first and in equal or larger type to that of the adopting or listing organization. ASSE International Mokena, Illinois Copyright

3 2017 Product Standards Committee Ed Lyczko Chairman Cleveland Clinic Retiree Cleveland, OH William Briggs Jr. MGJ Associates New York, NY Terry Burger NSF International Ypsilanti, MI William Chapin Professional Code Consulting, LLC Cullman, AL Mark Fish Zurn Industries, LLC Cary, NC Ron George Plumb-Tech Design & Consulting Services, LLC Newport, MI Daniel Gleiberman Sloan Los Angeles, CA John F. Higdon, P.E. Apollo Valves / Conbraco Industries, Inc. Matthews, NC Gary Howard Illinois Plumbing Inspector Retiree LaGrange, IL Conrad Jahrling (non-voting) ASSE International Chicago, IL Peter Marzec United Association of Plumbers and Pipefitters Pearl River, NY Thomas Pitcherello State of New Jersey Bordentown, NJ Daniel Rademacher Plumbing Code and Design Consulting Butte, MT Shabbir Rawalpindiwala Kohler Company Kohler, WI Billy Smith ASPE Montgomery, AL Tsan-Liang Su, PhD Stevens Institute of Technology Hoboken, NJ Chris B. Haldiman Watts Water Technologies Springfield, MO

4 LEC 2002 Working Group Tom Palkon Chairman IAPMO R&T Chicago, IL William Chapin Professional Code Consulting, LLC Cullman, AL Gregory Chernov, PE GE Appliances, a Haier Company Louisville, KY Tina Donda IAPMO R&T Mokena, IL Conrad L. Jahrling (non-voting) ASSE International Chicago, IL Ryan Prince GE Appliance, a Haier Company Louisville, KY ASSE International LEC for Shower Filters

5 FOREWORD This foreword shall not be considered a part of the standard, however, it is offered to provide background information. ASSE Standards are developed in the interest of consumer safety. Residential water treatment devices are designed to reduce contaminants from potable water. Consumers utilize water treatment products to improve the quality of the water they drink or use for washing, cleaning, bathing, and showering. Most water treatment products when installed become part of the plumbing system. Proper installation and care should be taken to ensure the integrity of the plumbing system remains in tack and complaint with plumbing codes. Recognition is made of the time volunteered by members of the Working Group and of the support of the manufacturers who also participated in the meetings for this standard. This standard does not imply ASSE's endorsement of a product which conforms to these requirements. Compliance with this standard does not imply acceptance by any code body. It is recommended that these devices be installed consistent with local codes by qualified and trained professionals. It is recommended that these devices be maintained and serviced per the manufacturer s recommendation, filters are replaced at regular intervals per the manufacturer s instructions and replace the entire system every 10 years. This standard was promulgated in accordance with procedures developed by the American National Standards Institute (ANSI). ASSE International LEC for Shower Filters

6 Shower Filtration Fitting for the Reduction of Chloramine SECTION I 1.0 General 1.1. Application Shower filters are designed to reduce contaminants typically found in potable water supply lines, such as chlorine and chloramine. The product improves the showering experience by reducing aesthetic contaminants from supply water Scope Description Shower Filter water treatment device. The major/critical components include: water filter s housing, filtration media, and shower head (when provided) or hand-held shower (when provided). The device is able to reduce chloramine, chlorine, or both. Shower filters, shower heads with integral filter, and hand held showers with integral filter are all fittings subject to ASME A / CSA B Reference Standards/Documents: APHA, Standard Methods for the Examination of Water and Wastewater, twentieth edition ASME A / CSA B Plumbing Supply Fittings ASME B (R2006) Pipe Threads, General Purpose, Inch ASME B (R2008) Dryseal Pipe Threads, Inch ASME B (R2008) Hose Coupling Screw Threads, Inch ASME PTC Pressure Measurement Instruments and Apparatus Supplement California Code of Regulations Title 20. Public Utilities and Energy, Division 2. State Energy Resources Conservation and Development Commission. CEC REV3 EPA WaterSense Specification for Showerheads, Version 1.0, March 4, 2010 ISO 228-1:2000(en) Pipe threads where pressure-tight joints are not made on the threads Part 1: Dimensions, tolerances, and designation NSF/ANSI Shower Filtration Systems Aesthetic Affects NSF/ANSI Glossary of drinking water treatment unit terminology NSF/ANSI Drinking Water System Components Lead Content ASSE International LEC for Shower Filters

7 SECTION II 2.0 Test Specimens 2.1. Samples Submitted Three (3) devices of each type, model and size shall be submitted by the manufacturer. Product bracketing can be used on similar design products to group products into families to reduce the number of products required for testing Samples Tested The testing agency shall select two (2) of each type, model, size, and family for each test. Tests shall be performed in the order listed in Section III of this standard. All tests shall be conducted on two sample unless otherwise specified in the standard Documentation Assembly drawings, installation instructions and other data which are needed to enable a testing agency to determine compliance with this standard shall accompany devices when submitted for examination and performance tests under this standard Rejection Failure of one (1) device shall result in a rejection of that type, model and size. ASSE International LEC for Shower Filters

8 SECTION III 3.0 Performance Requirements and Compliance Testing 3.1. High Efficiency Shower Head and Hand-Held Shower with Filter This section only applies to devices that are specified as high efficiency For high efficiency shower heads and hand-held showers that incorporate a filter cartridge, the device shall comply with the flow rate, spray force, and sections of ASME A / CSA B The minimum spray force for high efficiency shower heads and hand-held showers shall comply with the Spray Force test of ASME A / CSA B The minimum spray coverage for high efficiency shower heads and hand-held showers shall comply with the Spray Coverage test of ASME A / CSA B Flow Rate Purpose The purpose of this test is to determine if the flow rate meets minimum and maximum requirements at a low and high pressures and to establish the allowable range of the device s flow rate to be claimed by the manufacturer Procedures Maximum flow rate test shall be conducted at a static pressure of 80 ± 1.0 psi (552kPa ± 7kPa) and a temperature of 40 ± 2 C (104 F ± 3.6 F). The minimum flow rate test shall be conducted at a static pressure of 20 ± 1.0 psi (138kPa ± 7kPa) and a temperature of 40 ± 2.0 C (104 F ± 3.6 F) Connect the device to the apparatus as shown in Figure 1. Flow meter should be calibrated at target pressure and placed upstream of other instruments. Pressure gauge to be installed using a saddle tee on the pipe, with the pipe being drilled to create a 1/16-inch diameter hole (for ½-in nominal pipe size, or approximately 1/10 of the nominal pipe size) with square edge orifice and no burr. Flow rate shall be measured to within ±5% accuracy at target flow rate. Pressure shall be measured to within ±2% accuracy at target pressure. Temperature shall be measured to within ±2% accuracy at target temperature If measuring average flow rate over a given length of time, the container shall be able to collect water for at least 1 min and no longer than 5 min. The total volume of collected water shall be weighed in order to ascertain the volume. If using a flow meter, the flow meter should be calibrated at target pressure. ASSE International LEC for Shower Filters

9 Table 1 Flow rates required for given inlet pressures. High efficiency flow rate is defined by the EPA WaterSense Specification for Showerheads Maximum Flow Rate Minimum Flow Rate Pressure High Efficiency All Devices % of Maximum Flow Rate, or % of manufacturer s stated Maximum Flow Rate 20psi (140 kpa) 60% 45psi (310 kpa) 75% 80psi (550 kpa) 2.0gpm ( 7.8Lpm) 2.5gpm ( 9.5Lpm) Figure 1 Apparatus for evaluating the device to section 3.2. ASSE International LEC for Shower Filters

10 Figure 2 Dimension A shall be greater than 16 internal pipe diameters. Dimension B shall be 1-5 inches ( mm) Criteria The device s minimum and maximum flow rates shall be compliant to Table Chloramine Reduction Purpose The purpose of this test is to determine the shower filters ability to reduce chloramine from drinking water. ASSE International LEC for Shower Filters

11 Figure 3 Test apparatus for section 3.3 Chloramine Reduction Test Procedures Challenge Water Supply Challenge water used for testing shall be created using deionized water. Please see the table below for the concentration of the required chemicals and physical properties of the test water. Table 2 Influent Water Characteristics, i.e. Challenge Water ph 9 ± 0.25 Temperature Turbidity Alkalinity Chloramine (NH 2 Cl): Free available chlorine TDS 40 ± 2 C (104 F ± 3.6 F) < 1 NTU 80 ± 10 mg/l 2.0 ± 0.2 mg/l < 0.1 mg/l mg/l Hardness (as CaCO 3 ) 100mg/L ± 10% To adjust the water characteristics, use the following chemicals: ph To raise the ph use Sodium Hydroxide, NaOH, CAS To lower the ph use Hydrochloric Acid, HCl, CAS Alkalinity Sodium Bicarbonate, NaHCO 3, CAS TDS adjustment Sodium Chloride, NaCl, CAS Chloramine Ammonium Chloride, NH 4 Cl, CAS ASSE International LEC for Shower Filters

12 Chloramine Sodium Hypochlorite (10-15% active chlorine), NaOCl, CAS Hardness Calcium Chloride, CaCl 2, CAS Deionized water (<10mg/L TDS) When adjusting alkalinity and hardness, assure that the solution does not turn to a cloudy appearance, otherwise the filter will clog. If the solution does turn cloudy, this can be avoided by adding the CaCl 2 at a slower rate. Alternatively, a cloudy challenge solution can be treated using an appropriate sediment filtration system. Water parameters per Table 1 shall be confirmed after filtration Chloramine Formation (See Appendix A for a 200L (53gal) Example.) The Challenge water shall be adjusted for all other characteristics listed in except temperature. Ammonium chloride shall be added to the challenge water Diluted sodium hypochlorite should them be added to the challenge water to achieve a chloramine concentration per Table 2. Warning Do not combine Ammonia Chloride and Sodium Hypochlorite directly. Direct combination can produce a hazardous reaction and the release of chlorine gas. The challenge water shall be prepared at least 1 hour prior to starting the test. The concentration of chloramine and free chlorine in challenge water should be verified prior to starting the test The system should be assembled as per ASSE International LEC for Shower Filters

13 Figure 3. Water Pressure shall be set and maintained at 80 ± 2 psi (554kPa ± 14kPa) flowing pressure for the chloramine reduction test Two product samples shall be installed per the manufacturer s instructions. The samples shall be conditioned per the manufacturer s instructions per section using the challenge water at 40 C ± 2 C (104 F ± 3.6 F). After conditioning the test shall be initiated. The samples shall be tested using a cycle time of 15 minutes on and 15 minutes off Effluent water sample shall be collected every 10 ± 1% of the manufacturer s stated capacity up to 100% percent of the capacity. Effluent water samples shall be collected in the final 2 minutes of the 15 minute on cycle. The initial sample shall be collected after 5 gallons of water has passed through the filter. Collect enough water required for analysis. Product water shall be collected at a distance not to exceed 40.0 cm (15.7 in) from the outlet of the shower head. Samples shall be collected with minimal aeration. Chloramine analysis shall be conducted immediately after the sample is collected. Additional sample points may be taken beyond the 100% estimated system capacity in order to establish end of life for the filter. These sample points may be taken at any interval following the 100% sample point as determined by the manufacturer. Maximum run time shall be 16 hours per day. Minimum run time shall be 3 hours per day except for the final day, which will depend on the capacity of the device on test. ASSE International LEC for Shower Filters

14 Report format: Capacity Pressure Temperature Flow Rate Initial 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% ph Turbidity Alkalinity TDS Hardness Free available chlorine Chloramine Inf. Chloram Eff. Influent water samples shall be taken each day and analyzed for all water characteristics per Table 2. Influent Chloramine shall be sampled immediately prior the collection of the effluent sample to verify they meet the requirements of Influent challenge samples shall be collected immediately upstream of the test unit (see ASSE International LEC for Shower Filters

15 Figure 2). Influent temperature shall be measured immediately upstream of the test unit (see ASSE International LEC for Shower Filters

16 Criteria Figure 2). The influent temperature shall meet the requirements of during the entire ON cycle Claim for the reduction of chloramine may be made when tested in accordance with Section 3.3. The systems shall reduce an influent challenge concentration of chloramine by a minimum of 50% All effluent sample points must meet the requirement in in order to comply with this standard The last successful sample point determines the maximum claimed capacity of the filter If the filter does not meet the manufacturer s intended capacity during testing, the last sample point of 6 consecutively passing samples determine the capacity of the device Products that pass the chloramine test shall be allowed to make an equivalent claim for Chlorine without additional testing. ASSE International LEC for Shower Filters

17 3.4. Chlorine Reduction refer to NSF/ANSI 177 for chlorine reduction test procedure Criteria The device shall comply with the chlorine reduction test procedure in NSF/ANSI 177, or if the Chloramine Reduction test in section 3.3 was performed, see section Structural Integrity and Operation The device shall comply with the appropriate structural requirements referenced in NSF 177. See APPENDIX B for a list of the tests and clauses applicable Non-normative clauses for shower heads, hand showers, and body sprays The following clauses are for informational purposes only. These reference the appropriate sections that ASME A / CSA B125.1 requires for shower heads, hand showers, and body sprays, however are not required for compliance to this LEC. See APPENDIX B for a list of the tests and clauses applicable Structural Integrity and Operation The device shall comply with the appropriate structural requirements referenced in ASME A / CSA B Preconditioning and installation Shower head or body spray, hand shower, in-line shower filter assemblies, and adjusting mechanisms or function control devices shall comply with the Precondition and Installation requirements of ASME A / CSA B Backflow prevention Hand shower assembly shall comply with the Backflow Prevention test of ASME A / CSA B Ball joint leakage Shower head or body spray and hand shower shall comply with the Ball Joint Leakage test of ASME A / CSA B Hydrostatic Test In-line shower filter assemblies shall comply with the Hydrostatic Pressure test of NSF 177. Hand held shower hoses shall comply with the Hose Assembly Burst Pressure test section of ASME A / CSA B Coatings Shower head or body spray, hand shower, and adjusting mechanisms or function control devices shall comply with the Coatings Requirements of ASME A / CSA B Life cycle Shower head or body spray, hand shower, and adjusting mechanisms or function control devices shall comply with the Life Cycle requirements of ASME A / CSA B In-line shower filter assemblies separate from the shower head, body spray, or hand held shower shall comply with the Cycle test of NSF Life cycle hoses Hand shower shall comply with the Life Cycle for Shower Hoses requirements of ASME A / CSA B ASSE International LEC for Shower Filters

18 Mandrel strength Hand shower shall comply with the Mandrel Strength requirements of ASME A / CSA B Operation requirements Shower head or body spray, hand shower, and adjusting mechanisms or function control devices shall comply with the Operating requirements of ASME A / CSA B Pressure and temperature outlet blocked Shower head or body spray, hand shower, in-line shower filter assemblies, and adjusting mechanisms or function control devices shall comply with the Pressure and Temperature Outlet Blocked requirements of ASME A / CSA B Pullout strength Hand shower shall comply with the Pullout Strength requirements of ASME A / CSA B Resistance to installation loading thread torque strength Shower head or body spray, hand shower, and in-line shower filter assemblies shall comply with the Resistance to Installation Loading Thread Torque Strength requirements of ASME A / CSA B Resistance to use loading Hand shower shall comply with the Resistance to Use Loading requirements of ASME A / CSA B Threaded connections Shower head or body spray, hand shower, and in-line shower filter assemblies shall comply with the Threaded Connections requirements of ASME A / CSA B Torque Hand shower shall comply with the Torque requirements of ASME A / CSA B Spray Force High efficiency shower heads shall comply with the Spray Force requirements of ASME A / CSA B Spray Coverage High efficiency shower heads shall comply with the Spray Coverage requirements of ASME A / CSA B Function of shower head or hand-held shower assembly without filter Purpose If the shower head or hand-held shower assembly is designed to be operated without a filter, i.e. when the filter is removed, the assembly will still allow flow, section 3.7 will apply Test procedure Remove the filter and reassemble the device. Repeat section 3.2. If device is a shower head, test to section If device is a hand-held shower assembly, test to sections and Bypass Plug If the product can be installed with a bypass plug, obtain another device sample. Remove the filter from the device. Assembly the bypass plug into the device. Test the device per APPENDIX B for the type of device that it is, except do not perform sections 3.3 and 0. ASSE International LEC for Shower Filters

19 SECTION IV 4.0 Detailed Requirements 4.1. Materials and Hardware Materials Materials that internally come into contact with potable water shall comply with NSF/ANSI Hardware Coupling nuts, locknuts, and spout holding nuts shall be compliant with the Materials section of ASME A / CSA B Alternate materials shall comply with the Alternate Materials salt spray test of ASME A / CSA B Documentation Drawings Assembly drawings, schematics and other data which is helpful to the installer and needed by the testing agency to determine compliance with shall accompany the product when submitted for examination and testing under this standard Installation Instructions Instructions for installation, maintenance and testing shall be packaged with the device. These instructions shall provide information necessary to allow a correct installation Literature The device s literature shall state: the minimum rated flow rate in gallons per minute (liters per minute) at 45 psi (310kPa) and maximum rated flow rate at 80 psi (552kPa); general operation and maintenance requirements including, but not limited to, suggested frequency of filter replacement or service to the system, user responsibility, and parts and service availability; the rated capacity or rated service life in gallons (liters); statement noting the system and installation shall comply with applicable state and local regulations; the reduction performance claims; the statement: This device is not intended to be operated without the integral filter filter conditioning instructions. The device s literature may state the percent reduction of the contaminant or that it meets this LEC. ASSE International LEC for Shower Filters

20 Replacement Components The packaging or literature of components, specifically for replacement purposes, shall be labeled with the following information: - model number or name of component; - model number of system(s) in which the component is to be used - rated capacity/rated service life in gallons (liters); - operating or exchange steps Certificate of Compliance It is recommended that when showing compliance with this LEC that the certification document state the rated flow rate of the device per C Markings All Devices Each device shall have the following information marked on it or the packaging: - Name of manufacturer or trade mark - Type and model number of the device - Rated service flow rate in gallons per minute (liters per minute) - Rated capacity or rated service life in gallons (liters) - Reduction performance claims High Efficiency Devices and Hand Held Showers High efficiency devices and hand held showers shall comply with the marking requirements of A / CSA B Threads Pipe threads shall comply with one of the following standards: (a) Taper pipe threads, except dryseal, shall be in compliance with ASME B (b) Dryseal shall be in compliance with ASME B (c) Hose coupling threads shall be in compliance with ASME B Hand-held shower connection threads shall be ½-14 NPSM or ISO 228-G ½ B Shower heads for installation on standard shower arms shall be capable of being connected to a ½ NPT male thread. ASSE International LEC for Shower Filters

21 SECTION V 5.0 Definitions Definitions in the standard shall take precedence over any other publication. Definitions not shown are found in the Plumbing Dictionary (sixth edition) published by ASSE, or NSF 330. Bypass plug An accessory that allows a device to operate without its filter. Challenge water Water used during the contaminant test characterized by certain parameters. It is meant to test the capability of the device to reduce contaminants. Effluent water Water that is flowing out of the device. Filter housing The enclosure that houses the filter media, material, or assembly in the configuration required for a shower filter to perform its function. Filter media The aggregate substance that removes a pre-defined set of mixed chemicals, particles, etc. within the potable water stream flowing past it. Fitting (as repeated from the Plumbing Dictionary) Any device designed to control or guide the flow of water into a fixture. High Efficiency Shower Head A shower head fitting that reduces the flow rate to 2.0 gal/min (7.8 L/min). In-Line Shower Filter A shower filter installed upstream of a showerhead. Influent water Water that is flowing into the device. This is the challenge water. Shower filter An assembly installed in-line with or within a shower head that is able to remove a pre-defined set of mixed chemicals, particles, etc. within the potable water stream flowing through it. ASSE International LEC for Shower Filters

22 APPENDIX A This appendix shall be considered reference and not part of the LEC. The instructions below provide an example for creating a chloramine challenge tank consisting of: Challenge solution volume of X liters. NH 2 Cl concentration: 2.0 ± 0.2 mg/l For materials, see section Procedure: 1. Fill container with a volume of X liters of deionized (DI) H 2 O. 2. Start water circulation (mixing). 3. Add X * mg of NaCl and allow to dissolve completely. 4. Add X * 12.81mg of NH 4 Cl and allow to dissolve completely. 5. Measure and adjust alkalinity and hardness per section Measure and adjust ph to 9 ± 2.5 (NaOH to increase, HCl to decrease ph). Caution: use small amounts of the adjusting chemicals. 7. Add solution of NaOCl: measure 17.61mg of concentrate solution per X liters of DI H 2 O. Extract at least 10 parts of the current challenge solution. Mix the 1 part (17.61mg * X) of the concentrate solution into the extracted current challenge solution. Slowly add the diluted NaOCl into the challenge tank. Warning Do not combine Ammonium Chloride and Sodium Hypochlorite directly. Direct combination can produce a hazardous reaction and the release of chlorine gas. 8. Mix solution completely. 9. Stop water circulation (mixing). 10. Close the tank and allow to react for at least 1 hour. 11. Measure the concentration of free chlorine: if free chlorine is present, reaction is not complete, allow to react for another hour and repeat this step. 12. If free chlorine was undetected, measure the concentration of chloramine. 13. If chloramine concentration is low, calculate the amount of required NaOCl, go back to step 7 and add calculated amount. 14. If chloramine concentration is high, calculate the amount of required DI H 2 O, add calculated amount and go back to step 8. ASSE International LEC for Shower Filters

23 APPENDIX B This appendix shall be considered reference and not part of the normative requirements of this LEC. The following are the appropriate performance tests for showerhead and hand-held shower assemblies, as per ASME A / CSA B125.1 and this LEC. An X indicates that a particular test must be done to show compliance to the standard. Test LEC 2002 Clause ASME A / CSA B125.1 Clause NSF 177 Clause Shower Head with integrated filter Hand Held Shower with integrated filter In-Line filter (upstream of showerhead) Backflow Prevention X Ball Joint Leakage X X Chloramine Reduction 3.3 X X X Chlorine Reduction 0 X X X Coatings X X Flow rate X X X Functions without filter 3.7 X X Hydrostatic test Hose only 3.5, X , , , X , Life cycle / Cycle test , , , 5.6.2, X , , X Life cycle hoses X Mandrel strength X Operating requirements X X Preconditioning and installation and X X X Pressure and temperature outlet blocked X X X Pullout strength X Resistance to installation loading thread torque X X X strength Resistance to use loading X Spray Force (High Efficiency) X X Spray Coverage (High Efficiency) X X Threaded connections X X X Torque X ASSE International LEC for Shower Filters

24 Within the California Code of Regulations, Title 20, Division 2, there is a clause requiring the maximum shower head flow rates to be per Table H-5 in the State of California in section (H)(5), recreated below. Appliance Table B1 Maximum shower head flow rates per the California Code of Regulations. Manufactured on or after January 1, 1994 and prior to July 1, 2016 Maximum Flow Rate Manufactured on or after July 1, 2016 and prior to July 1, 2018 Manufactured on or after July 1, 2018 Showerheads 2.5gpm at 80psi 2.0gpm 80psi 1.8gpm at 80psi ASSE International LEC for Shower Filters

25 APPENDIX C This appendix shall be considered reference and not part of the LEC. The following method is to calculate the minimum equivalent length of pipe for the apparatus to perform the flow rate test per section 3.2 for alternative configurations. The pipe diameter should be determined to ensure turbulent flow regime for all design condition. To verify turbulent flow regime, calculate the worst case (minimum) Reynolds number (Re min ) using fluid properties at test temperature. For value of Re min should be greater than Calculate Re min using the following equation: Where: ρ water density (at test temperature) µ water dynamic viscosity (at test temperature) V free stream velocity D pipe diameter D max largest pipe diameter, D min smallest pipe diameter Q flow rate Q max highest test flow rate, Q min lowest test flow rate The pipe should have smooth walls so PVC pipe is recommended. The flow at the pressure tap should be fully developed. The length of the straight pipe directly upstream to the pressure tap should be greater that the entrance length (L e ) for worst case test conditions. Calculate L e_max using equation below: or Tap geometry: The diameter of the pressure tap should be approximately 1/10 th of the nominal pipe diameter. The tap should have square edge with no burr. The distance between the pressure tap and the device on test should be between 0.5 to 2.5 pipe diameters. ASSE International LEC for Shower Filters