Elkhart Brass Mystery J 350 and 500 gpm Master Stream Nozzle

A twist-shutoff nozzle for 350 and 500 gpm monitors

The Elkhart Brass Mystery J is a brass master stream nozzle with a twist shutoff. Elkhart lists the J at 350 gpm (1330 LPM) or 500 gpm (1900 LPM) at 100 psi (7 bar) with a 2.5 in inlet; the same Mystery family includes the JN at 1000 gpm and the CJK from 1250 to 2000 gpm with a 3.5 in inlet. The tip changes pattern under flow from straight stream to 90 degree fog, there is a grease fitting for lubricating the tip threads, and the finish is satin and cast brass.

It is a constant-flow design, so the nozzle holds a defined gallonage at its rated pressure, and it threads onto the 2.5 in NHT male outlet of an Elkhart monitor.

Specifications from the catalog

Elkhart publishes flow versus pressure charts for the J at 350 and 500 gpm, a reach at height graph for the J-500, a parts list and the instruction sheet on the Mystery product page.

Operation

The shut-off position is reached by turning the nozzle tip clockwise, viewed from behind, until it contacts the stem or baffle; some leakage is expected because the seal is metal to metal. Turning the tip counterclockwise opens the nozzle, and the first position reached is straight stream, marked with SS. Aligning the back edge of the tip with the line marked 30 gives narrow fog and with the line marked 90 gives wide fog. The stream setting changes the flow rate, so check the flow data for the setting used.

Open the supply valve slowly so that piping fills gradually and water hammer is avoided, and make sure personnel are clear of the stream path before flowing.

Inspection and maintenance

Inspect the nozzle after each use and at least monthly when idle, checking for damage and for bird or insect nests. Operate the tip through its full range several times. As required, turn the tip to wide fog and lubricate the threads through the grease fitting with one quick shot of grease; Elkhart recommends Mobilux EP 2, warns against over-greasing and suggests wiping excess grease off.

Choosing between the 350 and 500 gpm versions

The choice of flow rating should follow the water supply and the monitor rather than the other way round. Check what the pump or hydrant system can deliver at the monitor while other consumers are running, and choose the rating that the supply can sustain at the rated nozzle pressure. A nozzle that asks for more water than the system can provide will run below its rated pressure, which shortens reach and weakens the stream. Where the available supply clearly exceeds the J ratings, the JN or CJK from the same family may be the better fit, provided the monitor outlet suits them.

Because the nozzle threads onto a 2.5 in NHT male outlet, confirm the thread standard of the existing monitor before ordering. A thread mismatch cannot be solved on site without changing hardware, so this check matters most when the nozzle is meant for an installed monitor.

Typical application context

Master stream nozzles of this class are mounted on fixed or portable monitors that protect areas where large volumes of water must be applied from a distance: tank farms, loading racks, process units, storage yards, jetties and similar industrial sites, as well as on fire apparatus. The straight stream setting gives reach for attacking a fire or cooling exposed equipment from a safe position, while the narrow and wide fog settings spread the water for cooling and exposure protection closer to the monitor.

The twist shutoff allows the operator to stop the flow at the nozzle, but since the shutoff is metal to metal and some leakage is expected, the supply valve remains the means of fully isolating the monitor.

Commissioning and periodic testing

After fitting the nozzle to the monitor, carry out a flow test at the rated pressure. Open the supply valve slowly, move the tip through straight stream, narrow fog and wide fog, and observe the stream at each setting. Compare the result with the flow versus pressure charts and, for the J-500, the reach at height graph published by Elkhart. Record the pressure reading at the monitor during the test as a reference for later checks.

Include the nozzle in the regular inspection routine described in the instruction sheet and keep a log of each inspection and test, including any damage found and the lubrication carried out. A complete record makes it easier to spot gradual changes in stream quality or tip movement and to plan attention before the monitor is needed in an emergency.

How to specify your request

State the model Mystery J with the required flow rating, the finish, and the thread of the monitor outlet. Mention the monitor make and type if the nozzle will be fitted to existing equipment, and the quantity needed, so the request can be checked against the catalog data.

Confirm before ordering

Confirm the flow (350 or 500 gpm), the monitor outlet thread and finish, and compare with the JN for 1000 gpm or the CJK for larger monitors. The attached Elkhart instruction sheet covers installation and maintenance for the J and JN. Send the details for a quotation and see more Fire Fighting equipment.