Wet and dry barrels are different styles of hydrants for different types of applications. The terms “wet” and “dry” indicate whether or not there’s water left in the barrel of the hydrant when it’s not in use—the part which is above ground.
Dry Barrel Hydrants
The barrel of the hydrant is drained or pumped dry when the hydrant is not in use and the shut-off valve is located underground. here’s no water left above ground after the hydrant has been used, so the hydrant is safe from freezing in cold regions.
Wet Barrel Hydrants
The shut-off valves are above ground, so there’s water in the barrel even when the hydrant is not in use. Each outlet has a valve that operates independently, and the mechanical parts are easy to access above ground and can be adjusted to the proper height without expensive modifications. This makes dry barrel hydrants an easy to operate and easy to maintain choice for warm climates where there is no danger of freezing.
UL listed fittings for C900 PVC pipe are available. They are ductile iron mechanical joint fittings meeting AWWA C153 and ductile iron flanged fittings meeting AWWA C110. C900 PVC fabricated fittings and C907 molded PVC fittings are not UL list. C900 pipe is designed with equivalent outside diameters as ductile iron pipe so ductile iron MJ fittings, valves and similar appurtances are compatible with C900 PVC pipe for use in fire systems.
C900 is an AWWA standard, and is separate from UL listings and FM approvals. UL and FM have each issued separate standards for Underground Fire Service PVC distribution pipe. UL standard 1285 lists AWWA C900 pipe in sizes 4 to 12 inches with working pressures of 165, 235, and 305 psi for fire protection service. FM class number 1612 approves AWWA C900 PVC pipe rated class 150 (DR18) and class 200 (DR14) for fire protection service.
C900 is the AWWA standard for cast-iron-pipe-equivalent outside diameter polyvinyl chloride (PVC) pressure pipe and fabricated fittings for potable water transmission and distribution, covering nominal pipe sizes from 4 inches through 12 inches. The standard covers three classes of pressure pipe and dimension ratios (DRs):
DR 25 / 165 psi
DR 18 / 235 psi
DR 14 / 305 psi
C900 pipe and fittings must comply with the requirements of the Safe Drinking Water Act. PVC compounds and products must be in compliance with NSF/ANSI 61 certification for potable water service. The C900 standard does not include injection molded PVC fittings. Injection molded PVC fittings are covered in AWWA C907. C900 pipe is delivered in standard laying lengths of 20 feet +/- 1 Inch.
C900 pipe is also suitable for use in waste water force main services.
C905 is a comparable standard for potable water PVC pressure pipe, designed for pipe and fittings with nominal sizes over 12 inches.
PN10, PN16, PN25 and PN40 specify both pressure class in bars of pressure, and metric flange dimensions (such as bolt circle diameter, hole size, bolt size etc) according to international flange standards such as ISO 7005-1 or DIN 2501 that use the metric system of measurements. Flanges produced to ANSI, AWWA, ASA, or old British standards that are dimensioned in inches will not mate up with metric flanges in general. It is good practice when specifying a PN flange standard to indicate the actual working pressure since it is a common occurrence that a specific PN, say PN16, flange drilling is required on a fitting or valve to match adjacent flanges, but the pressure requirement is less than PN16.
A monitor hydrant is a specially configured fire hydrant. In addition to standard hose and pumper outlets, it has a special elbow on which can be mounted a fire fighting monitor. Monitors are uses in such places as oil fields, refineries, tank farms, petrochemical plants or other locations that have dangerous or flammable compounds. The monitor directs a spray of water, or other fire-fighting fluid towards the hazard. It can be turned on and left so that personnel can leave the area of immediate danger while the hydrant continues to hose the fire, chemical spill, or other dangerous situation.
MJ stands for Mechanical Joint. It is a type of compression joint designed for underground connection for pipe, valves and fittings. Mechanical joints allow for some deflection of the joint. This accommodates some misalignment of the two elements connected by the mechanical joint due to earth settling, or other installation issues while maintaining a seal under pressure.
Installation requires no mechanical skill. The components are comprised of a mechanical joint bell on the pipe, valve or fitting, and a mechanical joint gland, gasket and set of tee-head bolts and nuts which are supplied loose. The spigot end of a pipe receives the gland and gasket and is then inserted into the MJ bell of the connecting pipe, valve or fitting. The tee bolts are inserted through the bell and the gland. When the bolts are tightened, the gland and bell are drawn together which squeezes the rubber gasket that is between them. This compresses the gasket forcing it to press tightly against the pipe and make a seal. An MJ seal is rated for 350 psi for 2″ to 24″ fittings, and to 250 psi for 30″ to 36″ fittings.
While MJ pipe has fallen out of favor with the introduction of push-on ductile iron pipe, MJ valves and fittings are still the choice of most installers. MJ valves and fittings work equally well with push-on ductile iron pipe, as well as C900 PVC pipe, and IPS PVC pipe ( the latter requiring transition gaskets).
The AWWA C509 design standard was developed based on the physical characteristics of cast iron while AWWA C515 was developed based on the more robust physical characteristics of ductile iron. AWWA C509 standard was developed in 1980 to formalize the design standard for resilient seat valves for water and waste water. The wall thickness was adopted from the standard first published in 1952 for metal seated valves – AWWA C500. The wall thickness in C500 was, in turn, adopted from the original gate valve standard created in 1913 for cast iron valves with the wall thickness design based on the metallurgy of cast iron. The greater strength and durability of ductile iron allowed for the development of a valve design with reduced wall thickness while maintaining at least the same or greater resistance to internal working pressure with the added benefit of greater resistance to mechanical damage from transportation and handling.
The difference is in the micro-structure of the iron. Cast iron pipe for water transmission has been around since the 17th century. Cast iron pipe has great strength but lacks malleability so it is subject to mechanical damage in transit and handling which can be in the form of visually imperceptible hairline cracks. The development of ductile iron technology in 1948 led to a revolution in the iron pipe and fitting industry. Ductile iron is produced using more refined raw material. To the molten iron batch is added a highly controlled amount of magnesium alloy. This produces a drastic change in the microstructure causing the graphite to form spheroids rather than flakes, and a finer grain iron, giving the iron the ductility – making it much stronger, tougher, and resistant to mechanical damage in the form of cracks and outright shattering.
An indicator post, or an indicator post valve, is a valve assembly used to open or close the water supply main to a fire protection system. Post indicator valves are used in any application where responding firemen need a clear indication of the open or closed position of the valve, and an easy way to open or close the water supply from outside the building. Kennedy indicator posts and valves are UL listed and FM approved for this purpose.
The assembly consists of a conventional gate valve installed on the fire system water main, with the indicator post installed on a mounting plate on the bonnet. The top of the indicator post features a window that clearly indicates if the valve is open or shut.
Indigo Piping Systems supplies a complete range of post indicator valves for installation in any type of fire protection system. Available end connections include:
- Mechanical joint with accessories
- Mechanical joint with accessories and IPS transition gasket
- ANSI B16.1 class 125 flat faced flanges
- Tyton (push-on joint) for DI or C900 PVC
- Push-on joint for IPS PVC
- Mechanical joint x flange
Indicator posts can have either adjustable or fixed lengths to accommodate different bury depths. Adjustable indicator posts have a telescoping underground section for field adjustment to the exact bury depth needed. They are selected based on a combination of the depth of bury of the water main and the size of the valves. See the sizing matrix below to select the correct indicator post.
|Trench Depth Limits
Telescoping Barrel – Sizes B-E
|B Size||C Size||D Size||E Size|
|Maximum Trench Depth
Fixed Length Posts – Sizes F-H
|Valve||F Size||G Size||H Size|
Contact us today to request a quote on indicator post valves.