Valve Types & Turbo-Charging Sprinkler Valves


Valve Types

The three most commonly used valves are 1) ball valves, 2) sprinkler valves, and 3) sliding piston diaphram valves. Each has it's strengths and weaknesses. Each may be improved and the hot-rodding of valves will be discussed in a separate section.

Ball Valves

Ball valves are the simplest valves to build with. A simple, inline, connection is made between the air chamber and the barrel or breech. Operation is simple - just a twist or flick of the handle to operate the valve. They require no electrical or pneumatic energy to operate. One commonly sees these on entry level as well as non performance critical devices.

Ball valves also typically offer the lowest performance. It seems counter-intuitive that the performance is lower. It's also very sensitive to the operator's actions.

The reason is that high pressure air is going to start flowing (leaking would be an understatement) as soon as the smallest crescent of ball hole appears in the opening. This allows a significant portion of the air to begin to acellerate the projectile before the valve is entirely open. This is also the reason why it's sensitive to the operator - a person flipping the valve quickly will get better performance.

Ball valves do have an advantage in that they can often (do check!) be used in much higher pressure applications than sprinkler or other non metallic valves.

Ball valves have great utility for compact installations that either aren't performance sensitive - or whose performance isn't impacted by the relatively slow operation (such as with heavy projectiles)

Sprinkler Valves

Sprinkler valves are very popular. They can be faster than ball valves and they come as pre-assembled units (as do ball valves) . They also are remote if not electrical operatable. This allows the valve to be built in where it's convinient without worring about the operator (i.e. a ball valve needs to be placed where the operator can conveniently and comfortably operate the handle where as a remote operated sprinkler valve can be placed, for example, at the back of the device.

Sprinkler valves are typically electrically operated. They come with an elecrical solenoid that controls the operation of the valve (more on that later). The solenoids are designed to operate on 24 VAC. This would seem a problem but emperical evidence shows they'll operate satisfactorilly on two or three 9V batteries in series.

Sprinkler valves used for pneumatic canons do suffer from their hydraulic origins. They are designed to open relatively slowly to prevent water hammer damage to the plumbing. This adversly affects their performance for pneumatic canons. This performance impact varies by manufacturer. Rainbird and Toro are the best. I've seen other brands that opened so slowly they'd barely get a projectile out of the barrel (these seemed the weakest in construction as well).

It is fortunate that most sprinker valves can be hot-rodded in a number of ways. These typically have to do with working around or eliminating the design features that prevent water hammer. But an un-modified sprinkler valve can be as slow or slower than a ball valve - whereas a hot-rodded sprinkler valve can challenge the performance of a sliding piston valve.

Sprinkler valves also often come in inline, corner, and U form factors. Each has it's considerations for your designs based on availability as well as where you need the valve. The U valves typically have an anti-siphon feature and this can be a point of failure as well as a variable gas leak even if closing. The flow rate is typically {inline >> corner >> U} and the flow rates can vary widely between brands. So a 1" Rainbird inline != 1" Toro so read your specs.

Since Sprinkler valves are designed for household water systems they're typically limited to approximately (do check!) 150 PSI service.

Pilot Valve

A pilot valve is a special case discussed here. A pilot valve is a valve used to operate or control another valve. One could consider it a helper valve. Often you aren't aware that a valve is controlled by a pilot valve.

The electrical sprinkler valves are an example of a valve with a pilot valve. The electric solenoid controls a small valve. This small valve vents the top chamber of the much larger sprinkler diaphram valve chamber and causes the diaphram to either open or close as necessary. This is an internal pilot valve.

The hot-rodding process for a sprinkler valve may involve a high performance replacement for the solenoid. The blow gun of a blow gun operated sprinker valve is another example of a pilot valve. In this instance we've replaced a low performance pilot valve with a high performance pilot valve.

A Sliding Piston valve is not a pilot valve - but we'll mention it here as it's a commonly constructed valve that requires a pilot valve for operation.

The performance of a pilot valve can have an impact on the controlled valve - but the effects aren't quite as strong. For example, a slow pilot on a sprinkler valve can prevent useful operation, however, the difference between a decent sprinkler valve and a ball valve may not be noticable when controlling a sliding piston valve.

Diaphragm Valve

A diaphragm valve is a valve where a flexible diaphragm covers concentric (typically) inlet and outlet ports.

A great example of a diaphragm valve is a sprinker valve. The diaphragm is sandwitched inbetween an upper and a lower chamber. The lower chamber has concentric chambers and the diaphragm covers the inner chamber when closed this blocking air flow. The chambers are conentric. The inner chamber is the valve output. It's fed by the larger outer chamber. In operation there is a hole connecting the outer lower chamber and the top chamber. This is a small vent hole that equalizes the pressure between these chambers. This provides a larger high-pressure surface area that keeps the diaphram closed tightly against the smaller output (typically outside air pressure) output. When the top chamber is vented, however, there is a moderately large surface area (the outer, lower, input chamber) pushing the diaphram up into the top chamber. This forcibly breaks the seal and allows air to flow from the outer input chamber into the inner output chamber. For this to work, the vent hole must be small as the valve will close when the upper chamber reaches the pressure of the lower, outer, input chamber.  In sprinker valves, the venting of the top chamber is typically through an electric solenoid and, to prevent water leaks (keeping the valve water tight)  is vented into the output portion of the valve (which also serves to dampen valve speed).

A diaphragm valve may be used to construct an air cannon. A sealing disk of a flexible, but fairly stiff & sturdy plastic is positioned behind a barrel installed concentrically inside the air chamber. If "a little leaky" then air can vent between the sides to equalize the pressure and close the valve. A rearward stop of some sort must be positioned behnid the diaphragm to arrest it's rearward movement when the valve is fired - fired by venting the "rear chamber" portion that is delineated by the diaphragm. These can be tricky quick & consistent sealing (requiring a small gap) is somewhat in conflict with getting best air flow. A flexible diaphragm not positively arrested rearward can also (I've done it) get violently sucked out of position.

The issues of a conventional diaphragm valve can be overcome with a Sliding Piston Valve. While technically a diaphragm valve, in this variant the diaphragm is securely held in a carrier that can slide, without binding, in the chamber. This provides a very high flow diaphragm valve.

Sliding Piston

The issues of a conventional diaphragm valve can be overcome with a Sliding Piston Valve. While technically a diaphragm valve, in this variant the diaphragm is securely held in a carrier that can slide, without binding, in the chamber. When the rear chamber is vented, the entire assembly is forcibly slammed backwards uncorking the barrel. This provides a very high flow diaphragm valve that is durable and less finicky.

An example is a common design. A 4" air chamber has a 2" barrel concentrically installed, stopping about 4 inches from the rear of the chamber. A 3" coupler typically makes an acceptable sliding fit in 4" Sch 40 PVC. A thick rubber (1/4" or greater), or steel backed thinner rubber, disk is secured in one end of the coupler with a couple 1/2" rings of 3" pipe. This is installed in the back and tested to ensure an inch or so of smooth travel backwards from the sealed position. A gas-line tubing full circumference loop is installed behind the coupler to act as a shock absorber (don't skip this) and the back sealed up with a screw on rear cap (for servicability). The sliding piston valve is operated by a pilot valve. The pilot valve used is typically a ball valve or sprinkler valve .

Sprinkler Valve Theory

Electric sprinkler valves are commonly used for LAWs as well as Spudguns.

A  sprinker valve is a diaphragm valve. The diaphragm is sandwitched inbetween an upper and a lower chamber. The lower chamber has concentric chambers and the diaphragm covers the inner chamber when closed this blocking air flow. The chambers are conentric. The inner chamber is the valve output. It's fed by the larger outer chamber. In operation there is a hole connecting the outer lower chamber and the top chamber. This is a small vent hole that equalizes the pressure between these chambers. This provides a larger high-pressure surface area that keeps the diaphram closed tightly against the smaller output (typically outside air pressure) output. When the top chamber is vented, however, there is a moderately large surface area (the outer, lower, input chamber) pushing the diaphram up into the top chamber. This forcibly breaks the seal and allows air to flow from the outer input chamber into the inner output chamber. For this to work, the vent hole must be small as the valve will close when the upper chamber reaches the pressure of the lower, outer, input chamber.  In sprinker valves, the venting of the top chamber is typically through an electric solenoid and, to prevent water leaks (keeping the valve water tight)  is vented into the output portion of the valve (which also serves to dampen valve speed).


They're faster than manually operated ball valves, but slower than sliding piston diaphram valves. In p

Turbo Charging Sprinker Valves

Sprinkler valves are designed to minimize water hammer effects that can damage the downstream piping. This is typically acomplished by slowing the valve operation down. For pneumatic (air) vs hydraulic (water) applications the water hammer effect is negligible if non-existent. A significant increase in performance can be achieved by turbo charging the valves by re-designing the valves for the fastest operation possible. This will be more readily observed on lighter projectiles (paintballs, spuds) than with heavier projectiles (concrete slugs, ice slugs, metal).

The fastest operation can be achieved with conversion to non-electric operation. Some, however, prefer to retain electric operation, so the techniques, while not yielding the same performance, are also covered. I have left the D-III with both options so tha I could compare performance on a shot by shot basis. I suggest doing this on your prototyping cannon as the modifications are not mutually exclusive.

Turbo Charging Electric Solenoid operation.

This will provide a significant performance increase - though not so much as non-electric conversion. The advantages are easy remoting of the firing controls.

The vent air path is 1) a small hole from the upper chamber into the solenoid and/or it's housing, 2) the hole into the solenoid, 3) the output holes from the solenoid, and 4) the exhaust vent into the valve output line.
  1. The upper chamber vent hold is enlarged. This should be as big as possible up to perhaps 1/4". But consider the air feed to the solenoid. On the Rainbird, the solenoid's input seats against the top, outside, of the air chamber vent hole. Thus, this hole can be made only so large while still allowing the solenoid input to seal. This is significantly smaller than 1/4" and is the limiting factor on Rainbird valves. The drill selected for (2) the solenoid hole, is often the correct drill for this step for Rainbird valves.
  2. The hole into the solenoid is enlarged as much as possible. This must be done very carefully as a) the hold is inside an o-ring that provides a vent seal and b) the drill may grab and twist up into the solenoid ruining it. The current solenoids are potted and cannot be disassembed if ruined. You may have spares if you saved them from previous non-electric conversion. This drill bit is often the same and proper size as for the upper chamber vent hold.
  3. The output holes from the solenoid are enlarged. In the Rainbird these are typically much larger, in total area, than the input, so this is typically not a limiting factor and this step may often be skipped. As with the input hole, watch for the drill bit grabbing.
  4. The solenoid typically exhausts into the valve output line. This slows operation as the exhaust pressure delta is not fixed and against ambient pressure but is variable and rising against the main valve exhaust air as the barrel is pressurized and begins moving. This hole typically passes through the upper valve body, the diaphram, and the lower valve body. This is modified in two steps
    1. Plug the hole in the lower valve body that passes into the valve output. Be very careful to not contaminate and ruin the threads or slip fittings on the valve output. Be very careful to not ruin the diaphram seal area or the valve may leak. Rough up the hole to allow glue to set well. I've used PL Premium, epoxy, and glass filled epoxy all to good effect.
    2. Enlarge the solenoid exhaust hole as much as possible including but not limited to use of drills, dremels, etc. You are venting the solenoid exhaust air to ambient outside air pressure and want a low resistance path.
That's it. You can't do much else to turbo charge the electric operation of a sprinkler valve.

Turbo Charging for non-electric operation.

This will provide the fastest operation of the sprinkler valve this is possible. The goal is to vent the upper chamber as fast as possible. This requires a high air flow. The top of the air chamber is drilled and tapped for direct attachment of a blow gun. This is the method chosen in the Devastator-II cannon featured elsewhere on this website. I guarantee you will be most impressed by the performance increase - even over that of a turbo charged electric solenoid valve.

Care must be taken to find a suitablly strong spot to drill and tap. On Rainbirds the suitable spots are  the center "manual vent" of non adjustable valves, 2) the center on adjustable Rainbirds (remove and toss the adjustment mechanisms), 3) an unused round spot half radius off center on the top.

On the Devastator-II I directly mounted a blow gun to the center of the valve. On the Devastator-III, which uses a corner valve (vs the inline for the D-II), I installed a pressure safety valve in the center, and the blow gun remote feed to the off center spot.

I always seal the attachments, from the inside, with a bead of slow set epoxy. I have found both tape and paste teflon to not seal well against this plastic and found I ended up with epolxy anyway (or skip epoxy while prototyping and epoxy when ready to comitt). I also prefer the added strength provided by the epoxy (used sparingly of course).

If you will not be using the electric solenoid at all then you can remove the solenoid mount and pot up the remaining holes with epoxy. Be careful to prevent epoxy from flowing where you don't want it. (areas to consider are flowing into and ruining the upper chamber or it's seals and the output vent hold thus ruining your threads or permanently gluing your valve before it's ready).

Sprinkler Valve Brands

I suggest Rainbird over Toro over any other brands. The Rainbird is beefier and in particular has more plastic in support of the hot-rodding operations. The Toro is more compact. Otherwise, if you're not going for the last yard, either Toro or Rainbird is acceptable.

I will specifically caution against other brands and, in particular, would suggest testing any other brand in a prototype before comitting to a glue-in (or otherwise non-removable) build. As an experimental note, I was discussing a players new paintball cannon at a game. His cannon seemed to not have any power. As it turned out, it was an off brand valve picked up at a WalMart and it opened very slowly. Unfortunately this player had glued up his cannon (an otherwise great idea) and could neither remove and replace nor return the valve for refund.