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HYDRO-PRO: A Wet or Dry Sprinkler System
Designed for use in the State of Maine
Stephen B, Dodge, Editor
1993 Edition with 1998 Reference Notes
The intent of this design guide is to define an alternative sprinkler system installation which offers an enhanced level of life-safety to occupants evacuating a structure during the first minutes of a detected fire. The system design is not primarily intended to adequately protect the structure itself from fire loss or damage. A complete sprinkler system designed and installed in accordance with NFPA #13 may offer superior protection to the structure and contents.
Notice: An asterisk (*) following the number or letter designating a subdivision indicates explanatory material on that subdivision (if so included). Information on referenced publications can be found in Chapter 7.
Footnotes such as this and other inserted text in [brackets] are not part of the legal adoption of this sprinkler standard, but are inserted in this edition to assist the reader in clarifying how this standard is typically applied by State of Maine authorities who regulate the fire sprinkler industry.
Questions about this standard may be addressed to 207-626-3889, or fax 207-287-6251, or e-mail "firstname.lastname@example.org".
June 16, 2005
1-1.1* The wet sprinkler system herein described is an alternative design subject to permission for it's use by the Office of State Fire Marshal [Commissioner] exclusively. The system will ordinarily be permitted in buildings up to [and including]four stories in height, [above grade], which will fall into the following categories:
The lack of a water supply of sufficient capacity to support the normally installed N.F.P.A. #13 sprinkler system may be the determining factor in obtaining permission to use this alternative design. Any waivers shall be by special permission of the State Fire Marshal [Commissioner]. The burden of proof shall be on the requesting party.
*[Other considerations besides a lack of available town water are:
Even if town water is readily available, the Hydro-Pro is considered as a substitute for NFPA 13 or NFPA 13R if a pump would be required, because the pump set-up for NFPA 13 and NFPA 13R may be an unreasonable hardship compared to that of Hydro-Pro when evaluating the overall project. In any case, permission to use this standard must first be granted by the State Authority Having Jurisdiction.]
1-1.2 The dry sprinkler system herein described is also an alternate design to the wet application mentioned. See category listings in 1-1.1. In residential applications, wet systems shall be given priority. Dry systems will be allowed under special exception only, such as unoccupied areas.
1-2.1 This standard deals with the alternative design and installation of automatic sprinkler systems. It is a requirement to obtain permission for the use of the sprinkler systems described herein directly from the State Fire Marshal's Office [Commissioner] prior to preparation of plans and hydraulic calculations. Permission must also be obtained from all local authorities having jurisdiction.
1-3.1 Various levels of fire safety are available to dwelling occupants to provide life safety and property protection. This standard recommends, but does not require, sprinklering of all areas in a dwelling; it permits sprinklers to be omitted in certain areas. Such an approach produces a reasonable degree of fire safety. Greater protection to both life and property may be achieved by sprinklering all areas.
1-3.2 This standard assumes that one or more smoke detectors will be installed in accordance with the appropriate standard for the installation, maintenance and use of fire warning equipment.
Approved. Acceptable to the "authority having jurisdiction".
Authority Having Jurisdiction. The State Fire Marshal [Commissioner] shall be the authority having jurisdiction.
Backflow Prevention Device. A device that does not allow liquid to flow back to the supply and thus cause contamination.
[Commissioner. "Commissioner" means the Commissioner of Public Safety.]
Control Valve. A valve employed to control (shut off or turn on) a supply of water to a sprinkler system. This valve must be of an indicating type.
Check Valve. A valve that allows flow in one direction only.
Dry System. A system employing automatic sprinklers attached to a piping system containing air or nitrogen under pressure, the release of which (as from the opening of a sprinkler) permits the water pressure to open a valve known as a dry-pipe valve. The water then flows into the piping system and out the opened sprinklers.
Fire Department Connection. A threaded inlet connection located on the exterior of a building, arranged to enable the Fire Department to pressurize and supply the sprinkler system, bypassing the system control valves and supply main.
Labeled. Equipment or material which has attached a label, symbol, or other identifying mark of an organization acceptable to the "authority having jurisdiction" and concerned with product evaluation, that maintains periodic inspection of production of labeled equipment or materials and by whose labeling the manufacturer indicates compliance with appropriate standards or performance in a specified manner.
Listed. Equipment or materials included in a list published by an organization acceptable to the "authority having jurisdiction", such as UL or FM [which are nationally recognized independent testing laboratories], and concerned with product evaluation, that maintains periodic inspection of production of listed equipment or material and whose listing states either that the equipment or material meets appropriate standards or has been tested and found suitable for use in a specified manner.
Pre-engineered System. A packaged sprinkler system, including all components, designed to be installed according to pretested limitations.
Pump. A mechanical device that transfers and/or raises the pressure or flow of a fluid (water).
Residential Sprinkler Head. An automatic sprinkler specifically listed for use in residential occupancies.
Shall. Indicates a mandatory requirement.
Should. Indicates a recommendation or that which is advised but not required.
Sprinkler-Automatic. A fire suppression device which operates automatically when its heat activated element is heated to or above its thermal rating, allowing water to discharge over a specified area.
Sprinkler System. An integrated system of piping connected to a water supply, with listed sprinklers which automatically initiate water discharge over a fire area. This Design Guide requires sprinkler systems to include a control valve and a device for activating an alarm upon system operation.
Supply Pressure. Pressure within the water supply system (i.e. city or private water source.)
System Pressure. Pressure within the sprinkler system (i.e. above the check valve or other Backflow prevention device.)
Water Flow Alarm. An electrical sounding device activated by a water flow detector arranged to sound an alarm audible in all living areas over background noise levels with all intervening doors closed.
Wet System. A system employing automatic sprinklers attached to a piping system filled with water and connected to a water supply so that water discharges immediately from sprinklers opened by fire.
Chapter 2 Installation
2-1.1 Only listed new residential or commercial quick response head sprinklers shall be used in the installation of wet pipe life safety systems. [see 4.4.1]
2-1.1.1 Only listed commercial quick response sprinklers shall be used in the installation of dry pipe life safety systems. [see 4.4.1]
Exception 1: Standard sprinklers or fast-response sprinklers of intermediate or high temperature rating may be installed in areas of high ambient temperature.
Exception 2: Commercial dry pendant sprinklers shall be installed in areas subject to freezing.
2-1.1.2 Return Bends shall be used when pendant sprinklers are used on a dry pipe system (pipe and fitting shall be located in a heated area).
2-1.2 Only listed or approved sprinklers, materials, and devices shall be used in sprinkler systems.
1. Only U.L. listed fire pump jockey controller panel shall be installed.
Exception: Listing may be waived for tanks, hangers, water control valves and centrifugal pumps. All electrical components must be U.L. listed [to meet the NFPA 70 National Electric Code]. Waivers provided by the AHJ only.
2. Connections to water sources shall be as per NFPA #20. [1999 edition]
2-1.3 Pre-engineered systems shall be installed within the limitations which have been established by the testing laboratories where listed.
2-2.1 All new applications employing six (6) or more sprinklers and all rework applications employing twenty (20) or more sprinklers shall be submitted to the State Fire Marshal's Office [Commissioner] for approval.
2-2.2 Permits must be obtained for applications described in 2-2.1. Permits are subject to a fee schedule.
2-2.3 All submittals must be reviewed, and permits obtained prior to any installation.
2-3.1 The installer shall perform all required acceptance tests, complete the Contractor's Material and Test Certificate(s), and forward the certificate(s) to the local fire authority and the State Fire Marshal. [A copy of the permit must also be sent to the office of Licensing & Inspections signed & dated by the Responsible Managing Supervisor to verify that the system has been installed as it was designed and permitted. Also see 6-1.10.]
2-3.1.1 When the "authority having jurisdiction" desires to be present during the conducting of acceptance tests, the installer shall give advance notification of the time and date the testing will be performed.
2-3.1.2 All systems must be labeled with a hydraulic calculations name plate upon completion of the sprinkler application.
2-3.1.3 All above ground piping shall be hydrostatically tested at 200 p.s.i. for two (2) hours, in accordance with NFPA #13. [2002 edition]
2-3.1.4 During cold winter months, all dry systems may as an [temporary] alternative [for testing] be pneumatically tested at 40 p.s.i. operating air pressure. Any drop in air pressure greater than 2 p.s.i. over a 24 hour period shall be repaired and retested. When the temperature becomes above freezing, system shall be tested in accordance with 2-3.1.3.
2-3.1.5 Pumps shall be tested as per NFPA #20 [1999 edition] annually.
2-3.2 Underground mains and lead-in connections to system risers shall be flushed at the hydraulically calculated water demand rate of the system, in order to remove foreign materials that may have entered the underground piping during the course of installation. For all systems, the flushing operation shall be continued until water is clear.
2-3.2.1 To avoid property damage, provision shall be made for the disposal of water issuing from the test outlets.
2-3.2.2 Underground mains should be tested for leakage at 50 p.s.i. above maximum working pressure.
Chapter 3 Water Supply
3-1.1 Every automatic sprinkler system shall have at least one automatic water supply.
3-2.1 The following water supply sources are acceptable:
3-2.2 All stored water sources, other than pressure tanks, shall have an automatic filling mechanism set to regulate the available water supply volume from a minimum low water level equal to 110% of the calculated volume to a minimum high water level of 125% of the calculated volume, or, an audible water level alarm set to give a steady signal when the water level falls below 110% of the calculated volume. Tanks shall have covers and be protected against freezing. When stored water is used as the sole source of supply, the minimum calculated volume shall be equal to the hydraulic demand plus 10%. Stored supply shall be calculated for a minimum 30 minute period.
3-2.3 Systems using submersible pumps to provide method and height of mounting. Calculated volume information to be provided.
3-3.1 A piping system serving both sprinkler and domestic needs shall be acceptable when:
3-4.1 Every Hydro-Pro Sprinkler System supplied by a water utility shall be provided with the following:
Chapter 4 System Components
4-1.1 Each system shall have a control valve. The control valve shall be an indicating type, locked, electrically monitored or sealed in the open position.
4-1.2 Each wet pipe system shall have a half inch or larger drain and test connection with approved flow alarm device.
4-1.3 Each dry pipe system shall have an approved dry pipe valve with trim installed per manufacturer's specifications.
4-1.4 A 3.5" diameter pressure gauge shall be installed on the system side of the check valve, dry valve or backflow prevention device, in an accessible and visible location.
4-1.5 All test connections shall have an orifice size equal to the sprinkler heads installed. Test connections for dry pipe systems shall be in most remote area.
4-1.6 All drains shall be discharged to the atmosphere or to a suitable interior sanitary drain with air gap, as required by local or state plumbing codes.
4-1.7 All low points on dry pipe systems shall have a minimum of a half inch drain valve. All low points on dry pipe systems containing five or more gallons shall have an approved auxiliary drain as in NFPA #13. [2002 edition]
4-1.8 Air supply requirements shall be in accordance with NFPA #13. [2002 edition]
4-2.1 Whenever the word pipe is used in this standard, it shall be understood to also mean tube.
4-2.1.2 Pipe or tube used in sprinkler systems shall be as permitted by NFPA #13 [2002 edition]. The use of Chlorinated Poly Vinyl Chloride and Polybutylene tube capable of withstanding a working pressure of 175 p.s.i. shall be permitted provided that all such tubes are installed in accordance with their UL Listing. [...or a listing by a nationally recognized, independent testing laboratory.]
4-2.1.3 In dry pipe systems employing black steel pipe a C-100 shall be used in calculating friction loss.
4-2.1.4 Non-metallic pipe shall not be used in dry-pipe systems.
4-2.2 CPVC listed for exposed systems may be installed with the following restrictions:
4-2.3 Fittings used in sprinkler systems shall be as permitted by NFPA #13. [2002 edition]
4-2.4 Joints for the connection of copper tube may be soldered when used for wet pipe systems. Solder used shall conform to local plumbing codes [and NFPA 13].
4-2.5 Fittings for CPVC or Polybutylene tubing shall be compatible with , and capable of withstanding the same working pressure as the tubing being joined.
4-3.1 Piping shall be supported from structural members. This standard reflects hanging methods comparable to those used in local plumbing codes, and NFPA #13. [2002 edition]
4-3.2 Piping laid on open joists or rafters shall be secured to prevent lateral movement.
4-4.1 Only approved residential/commercial quick response sprinkler heads tested and listed by a [nationally] recognized, [independent] testing agency shall be used. [see 2-1.1 and 2-1.1.1], [Heads listed as "Residential" are only to be used within their listing specifications, with the exception in this standard of classrooms as stated in the exception to 5-1.5. Therefore, apart from this exception, if there is no overnight occupancy, then quick response heads must be used in place of residential heads, with 2 exceptions, as listed in 2-1.1.1.]
4-4.2 The sprinklers shall have fusing temperatures not less than 35 degrees F above maximum expected ambient temperature.
4-4.3 Fused, damaged, or painted sprinklers shall be replaced with sprinklers having the same performance characteristics as original equipment.
4-5.1 Local water flow alarms shall be provided on all sprinkler systems. (See section 1-5 for the definition of water flow alarm). The alarm shall be in a supervised location.
4-6.1 At least 3 spare sprinklers of each type, temperature rating and orifice size used in the system should be kept on the premises. When fused sprinklers are replaced by the owner, Fire Department or others, care should be taken to assure that the replacement sprinkler(s) is/are identical to that being replaced.
4-7.1 Each system shall include either a single or siamese 2 1/2" fire department connection with threads acceptable to local fire officials. Such connection shall be installed in accordance with NFPA #13 [2002 edition] and be readily visible and accessible.
4-8.1 All electrical wiring for the pump motor, magnetic contactors, switches, circuit breakers, alarms, etc., shall be in accordance with all applicable local, state and National codes. Pump motor base shall be at least 6" above the floor.[The intent is that the lowest part of the motor shall be at least 6" above the floor.] Starting loads and operating loads of pump motors must be considered in determining sizing of electrical feeds, breakers, and starting devices.
4-9.1 The pump power circuit shall be monitored.
4-9.2 Methods of monitoring the pump power circuit condition include, but are not limited to the following:
4-9.3 In all cases the pump power failure alarm should be wired so that an alarm indicator must remain "ON" until the pump power is restored. A silencing switch which deactivates an audible alarm but simultaneously activates a visual indicating light until the pump power is restored, is one means of accomplishing this objective.
4-9.4 Each system shall have a hydro-pneumatic tank with a bladder to allow for sprinkler operation in case of power failure. Such tanks shall be rated at a minimum of 100 gallons equivalency. [The bladder tank is to be hooked up on the system side of the check valve and main control valve but prior to the alarm device.]
Exception 1: A hydro-pneumatic tank is not required if system includes an auxiliary power generator. [...or gravity tank, or town water, or pressure tank for the water supply.]
Chapter 5 System Design
5-1.1 Design discharge. The system shall provide a discharge of not less than 12 gal/min per sprinkler. [See 5-1.4.2 about heads with listing specifications less than this, and see 5-1.4.3 about heads requiring more than this.]
5-1.2 Number of design sprinklers. The number of design sprinklers shall be 4 for wet pipe systems and 5 for dry pipe systems [even if the largest compartment contains less than this]. If a compartment contains more than the number of design sprinklers, only that amount must be calculated and those sprinklers must be adjacent to one another. [This applies whether the occupancy or occupancy area is light hazard or ordinary hazard 1 or 2. For areas that are not light hazard, do spacing according to NFPA 13, 2002 edition, and use a density of .15 gpm/sq. ft. for ordinary hazard 1, and .2 gpm/sq. ft. for ordinary hazard 2, or density listing of the head used for that hazard and coverage area. Regardless of the hazard type, hose demand is not required in the calculations. Hydro-Pro is never considered for Extra Hazard areas.]
5-1.2.1 The design area shall be that compartment or section of the building which is most hydraulically remote from the water supply.
5-1.2.2 The definition of "compartment" for use in determining the number and location of design sprinklers, is a space which is completely enclosed by walls and a ceiling. The compartment enclosure may have openings to an adjoining space if the openings have a minimum lintel depth of 8" below the ceiling.
5-1.3 Water demand. The water demand for the system shall be determined through hydraulic calculations, in accordance with section 5-1.2.
5-1.3.1 The maximum time for water to reach a test valve in the remote area of a dry-pipe system will be 60 seconds.
5-1.4 Sprinkler coverage. Sprinklers shall be spaced so that the maximum area protected by a single sprinkler does not exceed manufacturers specifications.
5-1.4.1 Maximum distance between sprinklers shall not exceed manufacturer's specifications. The maximum distance to a wall or partition shall not exceed one half of maximum allowable distance between sprinklers. The minimum distance between sprinklers within a compartment shall be 8 feet [unless the listing for the particular head(s) used varies from this]. The minimum allowable distance to a wall or partition is 4 inches.
5-1.4.2 The minimum operating pressure of any sprinkler shall be in accordance with the listing information of the sprinkler and provide the minimum flow rate specified in 5-1.1. Application rates, design areas, areas of coverage, and minimum design pressures other than those specified may be used with special sprinklers which have been listed for such specific installation conditions.
5-1.4.3 When commercial quick response heads are used, areas of coverage [for each head], application rates, densities and minimum design pressure should be as per NFPA #13 [2002 edition] for the hazard protected. [Regardless, only the 4 or 5 head calc is required according to 5-1.1 & 5-1.2. Kitchens outside of dwelling units are considered to be ordinary hazard 1. Vacant areas such as basements are considered to be ordinary hazard 1 or 2 depending upon potential of storage height.]
5-1.5 Position of sprinkler. Sprinklers shall be positioned so that deflectors are within 4 inches of a ceiling.
Exception: Special residential sprinklers shall be installed in accordance with listing limitations. [See 4-4.1 and 2-1.1 and 2-1.1.1.]
Exception: Residential heads shall be allowed in school classrooms.
5-1.5.1 Sprinklers shall be positioned so that the discharge is not obstructed by beams, light fixtures, or other obstructions. When tests are performed which show that sprinklers are positioned so that the discharge is not obstructed, sprinklers may be installed in accordance with the test results.
5-2.1 Dry-pipe systems. A sprinkler system containing pressurized air or nitrogen, the release of which (as from the opening of a sprinkler) permits the water pressure to open a valve known as a dry-pipe valve. The water then flows into the piping system and out the opened sprinklers. This system may be used in areas subject to freezing.
5-3.1 Piping shall be sized hydraulically in accordance with the methods described in NFPA13. [2002 edition]
5-3.2 The minimum pipe size shall be 3/4" on all systems using copper, CPVC, and polybutylene and shall be 1" for steel
5-4.1 Piping configurations may be looped, gridded, straight run or combinations thereof.
5-4.1.2 Gridded pipe systems shall not be accepted on dry-pipe systems per NFPA #13. 
5-5.1 Sprinklers shall be installed in all areas, including walk-in refrigerators, freezers and coolers.
Exception #1: Sprinklers may be omitted from all residential closets where the least dimension does not exceed 3 feet and the area does not exceed 24 square feet and the walls and ceiling are surfaced with non-combustible materials. [...or limited combustible materials.]
Exception #2: Sprinklers may be omitted from open attached porches in residential occupancies or with the approval of "authority having jurisdiction".
Exception #3: Sprinklers may be omitted from carports, garages, and similar structures if approved by the "authority having jurisdiction".
Exception #4: Sprinklers may be omitted from attics and accessible crawl spaces which are not used or intended for living purposes or storage.
Exception #5: Sprinklers may be omitted from unheated entrance foyers which are not the only means of egress [that has sprinkler protection].
Exception #6: Sprinklers may be omitted from bathrooms which are 55 square feet or less in area.
Exception #7: Special situations with the prior approval of the AHJ.
5-6.1 Scaled (1/8" or 1/4" = 1 foot) [or some similar type scale] and dimensioned drawings showing building and system layout, pipe sizing, ceiling heights and similar construction features shall be signed and submitted along with hydraulic calculations and manufacturer's data on sprinklers and plastic piping products to the State Fire Marshal [Commissioner] for review and approval prior to installation. Pump performance data and manufacturer's data shall also be included in the submittal.
5-6.2 Drawings and calculation shall be signed by a person holding at least a Level III certification with the National Institute for Certification of Engineering Technologies in layout of sprinkler systems, a Professional Engineer (P.E.) or a licensed Responsible Managing Supervisor (R.M.S.) Certification or registration numbers of the science shall be included with each submittal. Submittals shall include the following:
5-6.3 Proof of certification or registration shall be submitted to and kept on file at the State Fire Marshal's Office [Commissioner]. Expiration dates shall be clearly indicated on submitted documents. Drawings and calculations signed by a person whose qualification as submitted has expired will be rejected without review.
6-1 The responsibility for properly maintaining a sprinkler system is the obligation of the owner, who should understand the sprinkler system operation. A minimum monthly maintenance program should include the following:
6-1.1 Visually inspect all sprinklers to ensure against obstruction of spray.
6-1.2 Inspect all valves to assure that they are open.
6-1-3 Test all water flow devices.
6-1.4 The alarm system installed shall be tested.
6-1.5 Pumps. where employed, should be operated weekly in accordance with NFPA #20 [1999 edition]. Pumps shall be operated by causing a pressure drop by opening the Test Connection or a system drain valve fully for a minimum pump running time of two minutes.
6-1.6 The pressure of air used with pressurized water tanks shall be checked.
6-1.7 The water level in tanks shall be checked.
6-1.8 Care shall be taken to see that sprinklers are not painted either at the time of installation or during subsequent redecoration. When painting sprinkler piping or painting in areas next to sprinklers, the sprinklers may be protected by covering with a bag which shall be removed immediately after painting has been finished.
6-1.9 For further information, see NFPA #25. [2002 edition]
6-1.10 All sprinkler systems shall be tested at least once a year by means of the Test Connection. Certification as required by NFPA #25 [2002 edition] shall be filed with the State Fire Marshal [Commissioner]. [See 2-3.1]
6-1.11 The property owner shall notify the local fire department and their insurance company anytime that the sprinkler system has been temporarily or permanently turned off.
7-1 The following documents or portions thereof are referenced within this document and shall be considered part of the requirements of this document. The edition indicated for each reference is the current edition as of the date of issuance of this document.
7-1.1 NFPA Publications. The following publications are available from the National Fire Protection Association, Batterymarch Park, Quincy, MA 02269, [800-344-3555]
NFPA 13 (1991) Standard for the Installation of Sprinkler Systems, [Now 2002]
NFPA 20 (1990) Standard for the Installation of Centrifugal Fire Pumps, [Now 2003]
NFPA 22 (1987) Standard for Water Tanks for Private Fire Protection, [Now 2003]
NFPA 101 (1988) Life Safety Code, [Now 2003]
NFPA 13R (1991) Standard for the Installation of Sprinkler Systems in Residential Occupancies up to Four Stories in Height, [Now 2002]
NFPA 25 (1992) Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, [Now 2002]
[This has not been updated yet . See the Technical Policy by clicking "Back" at the top of your web browser, and then clicking on "Technical Policy" for changes to this state-fabricated fire sprinkler standard.] [3-31-08]
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