- Dry Weight: 19.5 pounds
- Wet Weight: 44.5 pounds
- PC/Reservoir Volume: 3 gallons
- Max Water Pressure: 70 PSI
- Air Receiver Volume: 272 in^3
- Max Air Receiver Pressure: 290 PSI
….3/16” Sweeper Nozzle* @ 70 PSI:
- Range: 64 feet (70 feet to the last drop)
- Output: 19.2 oz/sec
- Shot Time: 20 sec
….3/16” Forestry Nozzle** @ 70 PSI:
- Range: 59.5 feet (66.5 feet to the last drop)
- Output: 17.5 oz/sec
- Shot Time: 22 sec
….1/4” Forestry Nozzle*** @ 70 PSI:
- Range: 64 feet (69 feet to the last drop)
- Output: 24.4 oz/sec
- Shot Time: 15.75 sec
….3/8” Forestry Nozzle**** @ 70 PSI:
- Range: 72 feet (75 feet to the last drop)
- Output: 48 oz/sec
- Shot Time: 8 sec
* The sweeper nozzle came with an extra lip of brass at the outlet that should have been removed during the manufacturing process. To remove the lip, I chased the outlet with a 3/16” (0.1875”) drill bit, but the drill bit left scratches on the inside of the nozzle. I smoothed out the scratches with a Dremel rotary burr file by hand. I also rounded the outlet with a Dremel router bit by hand (brass is very soft). I read that rounding the outlet of an orifice allows more flow than a sharp edge. Of course, I later read that a sharp edge improves stream cohesion. After these processes, the outlet measured 0.189”.
** According to Alan Brackett at Cordova Precision (who used to make forestry nozzles), the gold-colored 3/16″ “forestry” nozzles were made as a promotional item to give away at trade shows. He said they are not approved for forestry use because they are not hard anodized. I also notice they have a straight internal profile (this is cheaper to machine than a convex or concave profile). All three of the forestry nozzles I tested have a short parallel section after the contraction. I have to imagine this actually causes drag and turbulence, contributing to this nozzles under-performance compared to the sweeper nozzle.
*** This forestry-approved, hard-anodized aluminum nozzle has a slightly convex internal profile. This nozzle has the same range as the sweeper nozzle, but wastes water much faster.
**** Alan estimates this nozzle was made in the 1970’s because it is crafted from nickel-plated brass. This old-school nozzle has a straight internal profile. This nozzle produced the most laminar-looking stream, likely because the large opening resulted in the lowest velocity.
I am holding the water blaster pistol a bit awkwardly in this video because I was operating my phone and the pistol at the same time, but you get the point.
BILL OF MATERIALS (BOM):
- QTY: 1 DESC: Teflon Paste Thread Sealant, 1.1 oz, “REAL-TUFF” SUPPLIER: SupplyHouse PN: 15605 Rated PSI: 12,000 Blaster PSI: 290
- QTY: 1 DESC: Teflon Tape Thread Sealant, 1/2″ x 14yd x 0.0032″ SUPPLIER: McMaster-Carr PN: 6802K33 Rated PSI: 10000 Blaster PSI: 290
- QTY: 2 DESC: Tank, 136 ci, 4″D x 13.75″L, 2.2 lbs, 1″-14UNS-2B, AL SUPPLIER: Catalina Cylinders PN: 2545 Rated PSI: 576 Blaster PSI: 290
- QTY: 2 DESC: Adapter, 1″-14UNS-2B x 1/4″ FNPT SUPPLIER: Catalina Cylinders PN: F1 Rated PSI: 576 Blaster PSI: 290
- QTY: 1 DESC: Cable Ties, Assorted Sizes, Black & White SUPPLIER: Amazon PN: N/A Rated PSI: N/A Blaster PSI: N/A
- QTY: 4 DESC: Close Nipple, 1/4″ NPT, Brass SUPPLIER: McMaster-Carr PN: 50785K152 Rated PSI: 1000 Blaster PSI: 290
- QTY: 2 DESC: Cross, 1/4″ NPT, Brass SUPPLIER: McMaster-Carr PN: 50785K233 Rated PSI: 1000 Blaster PSI: 290
- QTY: 1 DESC: Safety Relief Valve, Set at 300 PSI, 1/4″ NPT SUPPLIER: McMaster-Carr PN: 48435K72 Rated PSI: 300 Blaster PSI: 290
- QTY: 1 DESC: Schrader Valve, 1/4″ NPT, Plated Brass SUPPLIER: Schmidty Racing PN: 1/4-18 NPT-HP/T Rated PSI: 500 Blaster PSI: 290
- QTY: 3 DESC: 90-deg Street Elbow, 1/4″ NPT, Brass SUPPLIER: McMaster-Carr PN: 50785K43 Rated PSI: 1000 Blaster PSI: 290
- QTY: 1 DESC: 90-deg Elbow, 1/4″ NPT (M x M), Brass SUPPLIER: McMaster-Carr PN: 50785K123 Rated PSI: 1000 Blaster PSI: 290
- QTY: 1 DESC: Air Hose, 1/4” x 18”L, NPT (M x F), PVC SUPPLIER: McMaster-Carr PN: 5719K53 Rated PSI: 300 Blaster PSI: 290
- QTY: 2 DESC: Regulator, 1/4″ FNPT, 7-123 PSI Range SUPPLIER: Allied Electronics PN: ARX20-N02 Rated PSI: 290 Blaster PSI: 290
- QTY: 1 DESC: Plug, Hex Socket Type, 1/4″, Plated Brass SUPPLIER: Comes w/Regulator PN: N/A Rated PSI: 1000 Blaster PSI: 90
- QTY: 3 DESC: Face Bushing, 1/4″ x 1/8″ NPT, Brass SUPPLIER: McMaster-Carr PN: 4429K521 Rated PSI: 200 Blaster PSI: 90
- QTY: 2 DESC: Locknut, 1/4″ NPT, Brass SUPPLIER: McMaster-Carr PN: 50785K142 Rated PSI: 1000 Blaster PSI: N/A
- QTY: 2 DESC: Gauge, 0-160 PSI, 1″ Dial, 1/8″ NPT SUPPLIER: McMaster-Carr PN: 38105K51 Rated PSI: 160 Blaster PSI: 90
- QTY: 2 DESC: Safety Relief Valve, Multi-Range, 1/4″ NPT SUPPLIER: McMaster-Carr PN: 50265K23 Rated PSI: 200 Blaster PSI: 90
- QTY: 2 DESC: 90-deg Elbow, 1/4″ Push-To-Connect x 1/4″ MNPT SUPPLIER: McMaster-Carr PN: 5779K152 Rated PSI: 290 Blaster PSI: 90
- QTY: 9 DESC: Ft of Polyurethane Tubing, 1/4″ OD, 5/32″ ID, Green SUPPLIER: McMaster-Carr PN: 5648K69 Rated PSI: 175 Blaster PSI: 90
- QTY: 2 DESC: Straight, 1/4″ Push-To-Connect x 1/4″ MNPT SUPPLIER: McMaster-Carr PN: 5779K109 Rated PSI: 290 Blaster PSI: 70
- QTY: 1 DESC: Check Valve, 1/4″ FNPT Inlet, 1/4″ MNPT Outlet SUPPLIER: McMaster-Carr PN: 7768K22 Rated PSI: 500 Blaster PSI: 70
- QTY: 1 DESC: 3-Way Valve, 1/4″ NPT (M x F x F), Brass SUPPLIER: McMaster-Carr PN: 46095K51 Rated PSI: 500 Blaster PSI: 70
- QTY: 1 DESC: Reducing Bushing, 1/2″ NPT x 1/4″ NPT, Brass SUPPLIER: McMaster-Carr PN: 4429K422 Rated PSI: 200 Blaster PSI: 70
- QTY: 1 DESC: Tank, 3 Gallon, AL, (3) 1/2″ Ports SUPPLIER: KMW Performance PN: 111193 Rated PSI: 150 Blaster PSI: 70
- QTY: 1 DESC: Plug, Hex Socket Type, 1/2″, Brass SUPPLIER: McMaster-Carr PN: 50785K115 Rated PSI: 1000 Blaster PSI: 70
- QTY: 1 DESC: 90-deg Street Elbow, 1/2″ NPT, Brass SUPPLIER: Amazon PN: 3400X8 Rated PSI: 1000 Blaster PSI: 70
- QTY: 1 DESC: Adapter, 1/2″ MNPT x 3/4″ Hose Barb SUPPLIER: McMaster-Carr PN: 5346K68 Rated PSI: 250 Blaster PSI: 70
- QTY: 1 DESC: Hose Clamp, 3/4″ to 1-1/8″, Non-Perf, SS SUPPLIER: Amazon PN: 710-0580 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: 6′ Hose, 3/4″ ID, 15/16″ OD, PVC-Rein, Green SUPPLIER: MSC Direct PN: 48432009 Rated PSI: 105 Blaster PSI: 70
- QTY: 1 DESC: Compression Coupling, 1-1/4″, Flexible PVC SUPPLIER: McMaster-Carr PN: 4511K71 Rated PSI: 4.3 Blaster PSI: N/A
- QTY: 1 DESC: O-Rings, #213, 15/16″ ID, 1-3/16″ OD, EPDM (10 pk) SUPPLIER: McMaster-Carr PN: 9561K48 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Adapter, 3/4″ FGHT x 3/4″ Hose Barb, Swivel, Brass SUPPLIER: Amazon PN: BCF76 Rated PSI: 250 Blaster PSI: 70
- QTY: 1 DESC: Seat Post Clamp, BMX, 25.4mm, AL, Black SUPPLIER: ebay PN: FMF-484-Clamp Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Adapter, 3/4″ MGHT x 3/4″ MNPT, PP (10 pk) SUPPLIER: Savannah Hydroponics PN: 747264 Rated PSI: 75 Blaster PSI: 70
- QTY: 1 DESC: Pinch Valve, 3/4″ FNPT x 1″ FNPT, PP SUPPLIER: SpraySmarter PN: PV100-075 Rated PSI: 70/100 Blaster PSI: 70/100
- QTY: 1 DESC: Washer, 0.875″ ID, 1.125″ OD, Nylon, (50 pk) SUPPLIER: McMaster-Carr PN: 95606A570 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Screens, 20 Mesh, 1.25″ Dia, 304 SS (25 pk) SUPPLIER: McMaster-Carr PN: 9317T61 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Nipple, 1″ x 6″, PP (Actual ID: 0.95″) SUPPLIER: McMaster-Carr PN: 46825K47 Rated PSI: 150 Blaster PSI: 70
- QTY: 1 DESC: Straws, 1/8″ Dia x 7.5″ L, Plastic (1000 pk) SUPPLIER: Amazon PN: S1525A7 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Reducing Coupling, 1″ x 3/4″ NPT, PP SUPPLIER: McMaster-Carr PN: 46885K221 Rated PSI: 150 Blaster PSI: 70
- QTY: 1 DESC: Pipe, 3/4″ x 2′ L, Copper SUPPLIER: McMaster-Carr PN: 5175K135 Rated PSI: 700 Blaster PSI: N/A
- QTY: 1 DESC: Sweeper Nozzle, Smooth Bore, 3/4″ GHT x 3/16″, Brass SUPPLIER: Amazon PN: PSN76 Rated PSI: 100 Blaster PSI: 70
- QTY: 1 DESC: Forestry Nozzle, 3/4″ GHT x 3/16″, AL SUPPLIER: Western Fire Supply PN: 503-075034 Rated PSI: 200 Blaster PSI: 70
- QTY: 1 DESC: Forestry Nozzle, 3/4″ GHT x 1/4″, AL SUPPLIER: ebay PN: 503-075044 Rated PSI: 200 Blaster PSI: 70
- QTY: 1 DESC: Forestry Nozzle, 3/4″ GHT x 3/8″, AL SUPPLIER: ebay PN: 503-075064 Rated PSI: 200 Blaster PSI: 70
- QTY: 1 DESC: Close Nipple, 1/8″ NPT, Brass SUPPLIER: McMaster-Carr PN: 50785K151 Rated PSI: 1000 Blaster PSI: 100
- QTY: 1 DESC: Shim, 20mm OD, 14mm ID, 1mm Thk, SS (25 pk) SUPPLIER: McMaster-Carr PN: 98089A392 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Air Valve, 3-Port, 2-Pos, 1/8″ FNPT, with Trigger SUPPLIER: Amazon PN: TAC2-31V-Lever Rated PSI: 125 Blaster PSI: 100
- QTY: 2 DESC: Nipple, 1/8″ NPT x 3″ L, Brass SUPPLIER: McMaster-Carr PN: 4568K115 Rated PSI: 125 Blaster PSI: 100
- QTY: 1 DESC: Straight, 1/4″ Push-To-Connect x 1/8″ FNPT SUPPLIER: McMaster-Carr PN: 5779K129 Rated PSI: 290 Blaster PSI: 100
- QTY: 1 DESC: Muffler, 1/8″ FNPT Connection, 53 CFM SUPPLIER: McMaster-Carr PN: 4450K91 Rated PSI: 175 Blaster PSI: 100
- QTY: 1 DESC: Christmas Ornament Hook SUPPLIER: your mom PN: N/A Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Thimble for 1/4″ Wire Rope, Open End, Galv. Steel SUPPLIER: McMaster-Carr PN: 30335T1 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Handle Grip, 4.5″ L, Fits 1″ OD, Vinyl, Red (6 pk) SUPPLIER: McMaster-Carr PN: 97065K44 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Frame from M33A1 Riot Control Agent Disperser SUPPLIER: ebay PN: E116-3-131 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Shelf for Lightweight Rucksack Frame SUPPLIER: ebay PN: 8465-782-6722 Rated PSI: N/A Blaster PSI: N/A
- QTY: 1 DESC: Spec.-Ops. Brand Olive Drab Recon Ruck SUPPLIER: ebay PN: 100200202 Rated PSI: N/A Blaster PSI: N/A
Note: The quantity (QTY) listed above is the order quantity, not the quantity used; some items are listed as single-quantity because they come in the pack-quantity noted in the item description. The sequential numbers of this list correspond to the numbers in the assembly photos.
Water from a Garden Hose Spigot:
- QTY: 1 DESC: Washing Machine Hose, 3’ L, FGHT x FGHT SUPPLIER: Amazon PN: 16-1702
Water from a Lake, Stream, Etc:
- QTY: 1 DESC: Slide-N-Pump Water Siphon Pump, Size: Mini, 0.09375 gallons/stroke SUPPLIER: SkyMall PN: 375417
- QTY: 1 DESC: Garden Hose, 3’ L, MGHT x FGHT SUPPLIER: Amazon PN: HFZG503YW
- QTY: 1 DESC: Garden Hose Strainer, MGHT x FGHT, 120-Mesh SUPPLIER: Amazon PN: B007D43M5Q
- QTY: 1 DESC: Washing Machine Hose, 3’ L, FGHT x FGHT SUPPLIER: Amazon PN: 16-1702
- If available, fill as much as possible with an air compressor or regular bicycle floor pump first (not required).
- QTY: 1 DESC: Air Floor Pump, 0-350 PSI, w/Gauge SUPPLIER: Specialized Bicycle Components PN: Air Tool UHP
Air on the Run*:
- Fill with above air equipment first. If needed, attach a small pump with the items below (assemble in the order listed). Attach this assembly where the Schrader valve is shown in the photos. Clip the pump to the rucksack shoulder strap when not in use.
- QTY: 1 DESC: Reducing Bushing, 1/4” MNPT x 1/8” FNPT, Brass, 1000 PSI Max SUPPLIER McMaster-Carr PN: 50785K61
- QTY: 1 DESC: 90-deg Street Elbow, 1/8″ NPT, Brass, 1000 PSI Max SUPPLIER: McMaster-Carr PN: 50785K41
- QTY: 1 DESC: Hose, PTFE, SS Braid+Jacket, 32” L, 1/8” MNPT, 4500 PSI Max SUPPLIER: Paragon Performance PN: PP-PB-04A1-1831-CS-IN32
- QTY: 1 DESC: Reducing Coupling, 1/8” FNPT x 1/4” FNPT, Brass, 1000 PSI Max SUPPLIER: McMaster-Carr PN: 50785K181
- Schrader Valve (#9) from Main BOM Above
- QTY: 1 DESC: Convertible High Volume/High Pressure Pump, 0-300 PSI, w/Quick-Release Gauge SUPPLIER: Amazon PN: 00.4315.023.020
* Additional air is not necessarily required. The total amount of air needed depends on the following: how much water you put in the tank; your pressure regulator settings; and how many times you pull the trigger (the valve is air operated). If you operate at 70 PSI water pressure and expend 3 gallons over the course of many short trigger pulls, you will need additional air.
- Rotary Power Tool (Black & Decker RTX is my pick, but Dremel Tool is okay)
- Fiberglass Reinforced Cut-Off Wheel for Rotary Tool (Dremel Brand)
- Flap Sanding Wheel for Rotary Tool (Dremel Brand)
- 1/2” Drum Sander for Rotary Tool (Dremel Brand)
- Nut Driver or Wrench w/Socket (size depends on hose clamp you use)
- Tin Snips
- Metric & Standard Open-End Wrench Sets
- Metric & Standard Hex Wrench Sets
- Adjustable Wrenches
- 9/16” Thin-Head Wrench (McMaster-Carr, PN: 5403A13)
- Small & Large Pipe Wrenches
- Tongue & Groove Pliers (Channellocks)
- Miniature Side Cutters
- Screw Gun, Drill, or Drill Press
- Variable-Diameter Drill Bit, 5/8″ – 1-3/16″ (ebay, PN: 02X2, Size: CC2)
- Needle Nose Pliers
- Pipe Cutter
- Hose Cutter
Use thread sealant paste on all NPT connections. Even on connections where I used Teflon (PTFE) tape, I also applied this paste after the tape. I typically use both paste and tape on metal-to-plastic connections because metal and plastic have different thermal expansion and contraction rates, making these connections more likely to leak. Using both paste and tape on metal-to-plastic provides a more reliable leak-proof seal.
The Real-Tuff paste contains Teflon particles to fill thread imperfections and cracks. I chose this particular sealant paste because it is intended for use on both metal and plastic fittings. Most Teflon pastes (and Teflon tapes) are not recommend for plastic because their lubricity allows installers to overtighten fittings. Most thread sealants intended for plastic are not recommended for metal because their lack of Teflon does not provide enough lubrication for metal-to-metal connections.
Remove the brackets using a rotary power tool cutoff wheel. Smooth out any sharp edges with a flap sanding wheel. Alternatively, leave the brackets on if mounting to a board (example board mount).
Determine which direction you want the 90-degree elbow (#27) to point before tightening it. Do not cut the hose to its final length until everything else is assembled. Instead of plugging the side port with item #26, this connection could be used as the water fill port.
If you use a hose clamp that is larger than necessary, trim it shorter with tin snips to prevent the sharp metal from tearing the backpack or rucksack.
Determine which direction you want this assembly to point before tightening.
With all the carpet and cardboard in the background, you’ve probably figured out by now that I do not have a workbench (my vise is attached to a wall).
Loosely dry fit all of the above connections and arrange the water & air tanks in the rucksack or on the frame. Change the angles of the fittings as necessary. Make alignment marks on the fittings to replicate the angles more easily when tightening.
Use a pipe wrench to tighten item #4 to the brass assembly. After all the NPT fittings are assembled (except for the hose), thread #4 into #3. If you overtighten this, the o-ring will squeeze out or become damaged. If you under-tighten this, air pressure will blow out the o-ring. Item #5 has been employed by Ben in the past to retain the o-ring and prevent leaks.
Again arrange the tanks in the rucksack or on the frame. Install the male NPT hose connection in a way that the natural bend in the hose arcs over the water tank. If you bend the hose in the opposite direction of its memory, it can kink. The female end of the hose has a swivel connection that McMaster-Carr claims is NPT, but I doubt it. It looks more like NPSM, which is compatible with NPT. Nonetheless, I put Teflon tape and paste on this connection even though I’m pretty certain it only seals where the end of the male NPT fitting meets the NPSM bevel inside the female fitting.
Think twice before substituting the SMC ARX20-N02 regulators (#13) with something else. Folks in the Airsoft community use these SMC regulators because they are affordable and they are reasonably well balanced (probably because they are a piston-type regulator instead of diaphragm-type). What I mean by balanced is that the outlet pressure is not significantly affected by fluctuations in the inlet pressure (as long as the inlet pressure is still above the outlet pressure).
As noted in the BOM, the air tanks I used are Catalina Cylinders model 2545. I chose this model because I knew (after calculating) two of these would hold enough air for my purposes and would fit in my rucksack well. If you want about 28% more air, use the largest cylinder of this type, which is model 1602. It is the same diameter, just taller. I did not find any online retailers for Catalina’s low pressure cylinders; you must call their Cliff Impact Division at (757) 896-9100 to order. It might be worthwhile asking them if they have any stocking distributors.
Using HPA tanks instead of these low pressure cylinders would be slick, but I do not own a high pressure compressor, and I don’t want to run to the paintball store after every half-dozen uses (assuming 100 ci HPA tank). I’ve also read that using a hand pump to fill a 4500 PSI paintball tank takes forever. I was also not keen on the idea of using CO2 because I don’t want the ongoing expense of buying fresh CO2 tanks.
This gauge (#17) and face bushing (#15) should be preassembled before being attached to the pinch valve (#36). Otherwise, the face bushing will not thread onto the gauge fully without applying undue force on the plastic valve, which could crack it. The locknuts (#16) are only used for tightening face bushings; they are not a permanent part of the assemblies. Thread the locknuts onto the face bushing, and use two wrenches to tighten the locknuts against each other. Then, tighten the parts with a wrench on the outer locknut and a 9/16” thin-head wrench on the gauge. As you can see in the image above on the left, a regular wrench is too wide to make this assembly as low-profile as possible. I made a thin wrench from a refrigerator-door adjustment wrench by widening the opening with a hand file. However, buying the appropriate wrench from McMaster would have been easier.
Do not substitute the locknuts that I have specified with cheaper locknuts from McMaster. The cheaper locknuts are too wide to fit on the face bushing, and they actually have less thread engagement.
The pilot valve assembly should also be preassembled before attaching it to the pinch valve. Install the face bushing (#15) using the two locknuts. The 1/8” x 3” brass pipe nipples (#47) are difficult to thread into the pilot valve (#46); install them using a small pipe wrench. If the 90-degree corners of the pilot valve are uncomfortable in your hand, round the corners off a bit with a rotary tool flap sanding wheel.
The pilot valve above is a cheap knock-off of the Humphrey Products 31P valve with the 34C cam operator. I like the silver color of the knock-off. However, many people have minor skin reactions to nickel-plating. If cheap jewelry irritates your skin, go with the Humphrey version.
Remove the stop plate from the cam operator or it will interfere with the pinch valve body, and you will not be able to thread the pilot valve on all the way. I pried it off with an adjustable wrench in a few seconds, working it back and forth. This method deforms the cam operator bracket, but don’t bother straightening it out. It will straighten out on its own when you reinstall the cam operator as you tighten the retaining nut.
Remove the 1/4” plug and o-ring from the pinch valve; they are not needed. Also remove the two pinch valve ends to make assembly easier (do not wipe the lubrication off these fittings). To remove, put the hex of the valve-end in a vise and spin the valve off with a pipe wrench.
Anytime I use a pipe wrench or Channellocks on plastic fittings, I always put something between the wrench jaws and the plastic to avoid deep scratches. In this case, I used the compression coupling (#31) from the BOM. Remove the hose clamps from the compression coupling, and cut the rubbery PVC lengthwise with tin snips to end up with one rectangular sheet that you can wrap around plastic fittings when tightening them.
Trim a screen (#38) with tin snips to the appropriate diameter. Check the diameter against the very end of item #35 (NPT side). Insert the trimmed screen into the 3/4” NPT valve end of item #36.
Trim four nylon washers (#37) with tin snips, and insert them into the 3/4” valve end as spacers.
I ordered these nylon washers for the 1” valve end, but with this minor modification, they are acceptable for the 3/4” valve end, too. The resulting ID of these spacers closely matches the smallest ID of the 3/4” valve end.
These and the other spacers help hold the screens tightly in place by bridging the gap between the male NPT fitting and the screen. Additionally, the spacers help reduce turbulence because the water passes over the inside of the spacer rather than along exposed female NPT threads.
Thread the GHT adapter (#35) into the 3/4” NPT valve end (#36). These particular GHT adapters have a very loose NPT fit; so, I used Teflon tape (#2) in addition to Teflon paste (#1) on this connection.
I chose to use plastic 3/4” GHT x 3/4” NPT adapters because all of the metal ones I found (Anderson, Dixon, Kochek, Merit, etc) all had 1/2” NPT female threads inside the 3/4” NPT male threads. This makes the fitting more versatile, but not ideal for our purposes because the ID has a reduced diameter and a turbulence-inducing surface. A good plastic alternative to the part I used is Banjo part number GHMT075MPT. I did not use the Banjo part because it is only available in bright yellow.
Insert four nylon washers (#37) into the 1” valve end of item #36. These nylon washers do not need modification; their ID is very close to the ID of the 1” x 6” pipe nipple (#39).
Next, trim a screen (#38) with tin snips. Match the diameter of the very end of item #39, and insert the screen into the 1” valve end.
In this location, it is important to install the spacers before the screen so the flow-straightening straws (#40) all abut the same surface. In addition, these spacers provide a plenum space to allow water to distribute to all of the straws. JLspacemarine’s Nozzle Laminator lacks a plenum space, but Mark Fuller’s Patent indicates it is necessary.
Use the modified compression coupling (#31) and Channellocks to thread the 1” x 6” nipple (#39) into the 1” valve end of item #36. Make sure the pipe nipple is threaded far enough to engage the screen.
Then, cut the straws to length with side cutters. I used the first straw I cut as a template for all the rest. Insert the cut end of each straw towards the valve end screen. The straws must not stand taller than the pipe nipple after being pushed against the screen. Insert as many straws as you can without deforming their round shape.
I initially used regular drinking straws, but I was not satisfied with the stream cohesion. I tried different coffee sip stirrers, and I was most happy with the 3mm ones pictured above. Others were either too flimsy or had a septum in the center that seemed to cause excessive pressure drop. If you are looking for something larger than coffee stirrers, but smaller than regular drinking straws, you might want to try these 4mm straws.
Use a variable-diameter drill bit to make a smooth contraction from the 1” side of the reducing coupling to the 3/4” side. It would be best to use a drill press, but I don’t have one so I used a screw gun. To match the ID of item #39, which later threads into the reducing coupling, I had to drive the variable-diameter drill bit in as far as possible without damaging the 1” NPT threads.
You can skip this step if you want, but the smooth contraction should help keep turbulence down to a minimum.
Use a pipe cutter to cut a 5/16” long spacer from 3/4” copper pipe (#42). Use a rotary tool sanding drum to remove the lip created by the pipe cutter and to sand the inside of the pipe smooth. Then, insert the spacer into the 3/4” NPT side of the reducing coupling. Finally, trim a screen with tin snips, and insert it over the copper spacer.
The ID of the 3/4” copper pipe is a close match to the ID of the 3/4” GHT adapter (#35), and the OD of this copper is a close match to the ID of the 3/4” female NPT threads of the reducing coupling.
I have two feet of the copper pipe on the BOM because that is the minimum you can buy from McMaster. However, you may be better off seeing if Home Depot has any scraps. Rather than buying the copper, I removed the 3/4” pipe connected to the safety valve on the hot water heater at my house. I cut off the little bit I needed, then threaded the pipe back onto the safety valve.
Thread the GHT adapter (#35) into the 3/4” NPT side of the reducing coupling (#41). Again, because the GHT adapters have a very loose NPT fit, I used Teflon tape (#2) in addition to Teflon paste (#1) on this connection.
Next, trim a screen (#38) with tin snips. Match the diameter of the very end of item #39, and insert the screen into the 1” side of the reducing coupling.
Use the modified compression coupling (#31) and Channellocks to help thread the 1” x 6” nipple (#39) into the 1” end of the reducing coupling (#41). Make sure the pipe nipple is threaded far enough to engage the screen. If you have trouble threading it all the way, you can put some nylon washers (#37) between the screen and the reducing coupling (do not put them between the screen and the pipe nipple).
Thread a nozzle such as item #43c onto the GHT adapter (#35).
Above are the four GHT nozzles that I tested. Be careful when ordering sweeper nozzles; most do not have a smooth bore on the inside. Step-drilled sweeper nozzles do not perform as well. The forestry nozzles have a short, smooth taper followed by a short parallel section before the outlet. As suggested by my range tests, this geometry is not ideal. You might achieve better results than me by modifying sweeper nozzles to a larger diameter rather than buying forestry firefighting nozzles.
If you insist on having forestry nozzles because they look cool and you order them using the part numbers I have provided, what you get may look different on the outside AND inside. I suspect that many newer (1980-ish to present) nozzles approved for forestry use (43c) have a convex internal profile. Non-forestry-approved nozzles (43b) and nozzles made of nickel-plated brass from back-in-the-day (43d) have a straight internal profile. The convex profile doesn’t seem to work as well. The exact 43b nozzle above is still available from Western Fire Supply, but once their limited stock runs out only the newer-style will be available. You may have to purchase 43c and 43d used on ebay to get the best possible internal profiles for forestry nozzles of those sizes.
Attach the valve end assemblies, pilot valve assembly, and the gauge assembly to the pinch valve body. Be careful not to overtighten the valve end assemblies. If you make one valve end a little tighter than necessary, there is no ill effect. However, if you install the second one too tight, the pinch valve tube inside will twist, and the valve will not seal properly. The valve ends come pre-lubricated from the factory (to prevent the valve ends from twisting the tube), but you may need to apply more silicone lubricant after handling the valve ends so much.
When installing the pilot valve assembly, use shims (#45) between this assembly and the pinch valve body. The pilot valve, shims, and valve body should all be tight against each other to distribute recoil forces properly during operation. Otherwise, recoil force could cause the metal male NPT threads to leverage and ruin the plastic female NPT threads. You may have to experiment with different quantities of shims to allow the trigger to point in the correct direction with the assembly parts tight against each other.
The shim used between the gauge assembly and the pinch valve body is purely aesthetic. Again, you may have to experiment with a different number of shims to get the assembly parts tight against each other and have the gauge facing the direction you want.
If you plan to use a rucksack or backpack to hold your tanks, put the modified compression coupling (#31) over the brass street 90 (#27) at the bottom of the water tank. This will prevent the fitting from wearing through the fabric.
Put the water tank and air tanks in the rucksack (or attach/install as applicable).
Old school military frames made from the 1960’s to the 1990’s provide breathing room between the frame and your back, so you don’t sweat as much. A frame does add some weight, but it makes a load feel tens of pounds lighter. Furthermore, these soaker components and water feel even lighter (compared to a normal rucksack load of the same weight) because they comprise a denser, smaller-volume load that is close to the body. A typical rucksack load projects further from the body.
Regardless of what rucksack frame or hiking frame you use, it helps to have a shelf for the water tank to sit on. The load sags without it; the load feels lighter when it is positioned higher. What is nice about the shelf above (and the one used on the Ubersoaker) is that the shelf is deep enough to support the tank, but shallow enough to not obstruct the bottom water hose connection.
Tubes 20a, 20b, and 20c are all cut from item #20 on the BOM. Tube #20a pressurizes the water tank; tube 20b is an air bleed for filling. Do not mix up these hoses. Tube 20c pressurizes the pinch valve. I used EPDM o-rings (#32) to attach the 20c tubing to the water hose.
You can substitute cable ties for the o-rings. I used the o-rings because I don’t like how exposed cable ties look. Ranger Bands, which are made of EPDM, were my inspiration for using these o-rings. EPDM has good elasticity.
Put the rucksack on your back, and hold the pinch valve pistol in your hand to determine how long the water hose (#30) should be. Take into account that you will need to aim high or across your body at times. Also consider whether you want to route the hose under your arm or on the outside of your arm. For me, routing the hose under my arm was more comfortable and kept it tighter to the pack and my body.
Cut the hose, and slide on the clamp (#34). There is a lip on one side of the clamp ID; the cut end of the hose should be in contact with the lip. Push the brass GHT adapter (#33) into the end of the hose; you might need to use water as a temporary lubricant to get it on. Connect the assembled hose end to the plastic GHT adapter (#35) of the pinch valve pistol.
Obviously, I could have used a hose clamp instead of a BMX seat post clamp, but I don’t like the look of exposed hose clamps. If you use a hose with a different OD than the one I specified in the BOM, a 25.4mm diameter seat post clamp may not be adequate to hold your hose on.
Route the air tubing (#20c) around the gauge and down the trigger side of the pilot valve assembly. Use tin snips to trim the tear-drop-shaped thimble (#51), and use needle nose pliers to shape the thimble into an arc that will not allow the air tubing to crimp. Attach the air tubing to the thimble with two cable ties (#5), and use side cutters to trim the unused portion of cable tie. Slide the cable ties a little bit toward the center of the thimble. Otherwise, they will be pushed out of position when installing the handle grip.
The ornament hook (#50) is needed to prevent the tube from sliding out of the push-to-connect fitting when installing the handle grip (I was unsuccessful without it). I wrapped the hook wire around the plastic collar twice before twisting it and trimming it with side cutters.
Make a hole in the bottom of the handle grip so the pinch valve air can exhaust properly. I used a gasket cutter to make the hole in the handle, but using the variable-diameter drill bit or a regular drill bit would be fine. The hole does not have to be this big.
Push the handle grip over the pilot valve air assembly. This is a tight fit; use water as a temporary lubricant.
Assembly is now complete.
- Turn the handle of the 3-way valve (#23) to Position 2 (180 degrees from Position 1) to vent the water tank.
- If you are using the same adjustable safety relief valves (#18) that I used, install the appropriate color-coded springs per the instructions that come with the safety valves.
- Lift up on the air regulator (#13) adjustment knobs to unlock them if they are in the locked position.
- Turn the air regulator adjustment knobs all the way counter-clockwise to bring the regulator set points to 0 PSI.
- Loosen the safety valve adjustment locknuts if they are tight.
- Turn the safety valve adjustment knobs all the way clockwise to bring the set points as high as possible.
- Fill the air tanks to 290 PSI with a compressor, a manual pump or a combination of both through the Schrader valve (#9).
- Adjust the regulator that pressurizes the water tank up to 80 PSI.
- Adjust the safety valve of that same regulator so that it opens fully at 80 PSI. The pinch valve is rated for 70 PSI water pressure inside the pinch tube, but a safety valve set to open fully at 80 PSI will start to crack open 5 to 10 PSI below the setting.
- Adjust the water tank air regulator to 70 PSI or less for operation. Push down on the adjustment knob to lock it.
- Adjust the regulator that pressurizes the pinch valve up to 110 PSI. The gauge is located on the pinch valve.
- Adjust the safety valve of this regulator so that it opens fully at 110 PSI. The pinch valve is rated for 100 PSI air pressure on the outside of the pinch tube.
- Adjust the pinch valve air regulator to 100 PSI or less for operation. Push down on the adjustment knob to lock it. The manufacturer claims that a good seal can be achieved with 15 to 20 PSI above the water pressure setting, but I’ve only been getting a good seal with a ~30 PSI differential.
If you do not need the flexibility of adjustable safety valves, substitute them for fixed set point safety valves. Then, you only have to adjust the air regulators.
I used a fixed set point safety valve (#8) for the air tanks. I chose a 300 PSI safety valve because the published working pressure of my lowest-rated component in that part of the circuit is 290 PSI. I can start to hear this safety valve relieve at about 295 PSI.
- Turn the handle of the 3-way valve (#23) to Position 2 to vent the water tank and isolate it from pressurized air.
- Fill the air tanks to 290 PSI with a compressor, a manual pump or a combination of both through the Schrader valve (#9).
- Remove the nozzle (#43) from the pinch valve pistol, and attach a garden hose or manual pump.*
- With the pistol trigger depressed,* fill the water tank to the desired level.
- Turn the handle of the 3-way valve to Position 1 to pressurize the water tank. If you did not fill the water tank all the way, this will cause the air tank pressure to drop below 290 PSI.
- If applicable, fill the air tanks back up to 290 PSI to maximize air storage (I did not install a gauge on the tanks, I use the gauge that came with the manual pump).
- Affix your nozzle of choice, and enjoy.
*Instead of filling through the pistol, you can attach a dedicated fill line (with GHT valve and quick connectors) to the side port on the water tank that I plugged (#26).
To fire, simply pull the trigger of the pilot valve (#46). To stop firing, release the trigger.
Keep an eye on the gauge on the pinch valve pistol. When the pressure starts to drop, you know you are low on air. Another indication of low air is leakage through the pinch valve when the trigger is released. If you have the onboard air pump mentioned in the Fill Equipment section of this guide, pump away and the leaking will subside when the gauge above is about 25 to 30 PSI greater than wherever you set the water pressure regulator.
You know the water level is low when the pack feels very light. You might be able to judge the level a little better by shaking your back to hear and feel the sloshing. If you want more accurate level indication, add a “sight glass”. Install a Tee between item #27 and item #28, and add a Tee between item #22 and item #23. Then, add the appropriate fittings to connect tubing like item #20 between the added Tees. You would have to install a grommet (like McMaster part # 9610K18) in the bottom of the rucksack to route the tubing out, up along a shoulder strap, and back in the top.