2" rpz

The glossy metallic red won’t be everyone’s choice–however the Superior Bikes XP 919 is also available in black. The frame has internal routing although the plug in the frame doesn’t look like it can support an internal dropper post if that was something you wanted to look at. The frame has modern boost axle spacing, and without a chain or seat stay bridge there is plenty of room for wider tyres and mud. There’s a press fit bottom bracket shell, tapered head tube and room for two bottles in the frame’s main triangle.

I’ve got the XP 919 ($1999) on test, which is an alloy frame with a Shimano 12-speed group set and brakes, RockShox 100mm fork and a smart cockpit arrangement. Coming in at about $2000, the XP 919 sits at a very competitive part of the market. It goes up against the Marin Team 1 from BikesOnline and the Merida Big.Nine SLX. When we reviewed 8 hardtails under $2000 last year, we had one guiding question; is it fun to ride?

Superior Bikes come out of the mountains in the Czech Republic, and they are now available in Australia via BikesOnline. With over 30 years making bikes, Superior have had a recent push into the elite cross-country market, but not without ensuring that a strong foundation remains in a hardtail line up. Superior Bikes have a range of carbon and alloy hardtails, starting at $1999 with the Superior Bikes XP 919 and offering just about everything you would expect. This includes 29” wheels, boost through axles, wide range 12-speed gearing and great ergonomics. The Superior XP range clearly has a cross-country intent, and is therefore built around 100mm travel forks and moderate geometry.

RPZ diagram

On rougher descents with small rock drops, bigger exposed roots and more rock, the XP 919 still holds its own. Without a dropper and with basic tyres you need to be mindful of line selection, and understand that a Judy fork won’t have the ongoing midstroke support and balance through extended rock sections that a top-spec fork will have. Overall though, I was still really impressed. A lot of this is down to the ergonomics of the cockpit. From saddle comfort to bar width, bar sweep and stem length, I was really comfortable with the fit and handling on the Superior Bikes XP 919. The bike offered no surprises and the overall performance is a good baseline to improve on with a few smart upgrades overtime.

Photographer: Gerard LaganaTester: Mike BlewittRiding Experience: Hardtail aficionadoGenerally Rides: Norco Revolver 120 HT, Factor Lando XCHeight: 178cmWeight: 72kgBike Test Track: Greater Brisbane

RPZ Valve price

It is possible to build a double check valve assembly from new components, but this is not the best option as there is a high risk of built assemblies not meeting local code. A better option, for convenience, cost-effectiveness, and coding restrictions, is to purchase a pre-assembled double check valve assembly.

RPZ vs double check

Double check valves (DCV, also called double check assemblies or DCA) are a good choice for underground or indoor installations. A DCA consists of an inlet shutoff valve, two independently operating spring-loaded check valves (usually inside a single valve body), four test cocks, and an outlet shutoff valve. If local building codes allow for it, you must install Double check assemblies vertically.

The DCA is the most common type of approved backflow prevention device for use in underground or in-line installations. In-line (or below-grade) simply means that the backflow device is parallel with the piping of the sprinkler system; unlike the PVB, the DCA does not have to be installed 12 inches above the highest point in the system. Some areas do require above-ground installation, so check with local authorities before installing below ground.

Several factors must be taken into consideration when selecting a backflow device. These include local building codes regulating backflow preventers, the size of the landscape to be irrigated, and where the backflow preventer is going to be installed. It’s a good idea to familiarize yourself with the different types of backflow devices. It will help you to select the one that best meets your requirements.

At $1999 the Superior XP 919 sits in a very competitive part of the market. For riders looking for a fun bike to get out onto the trails it’s a great place to start. But for more off-road performance I’d suggest investing in tubeless tyres, valves and sealant–plus a shock pump–to truly take advantage of the bikes handling and characteristics.

The image above shows the Febco 825Y Reduced Pressure Zone Backflow Preventer. Shop for this and other backflow preventers at SprinklerWarehouse.com.

With wide 760mm flat bars and a comfortable Fizik seat, the XP 919 was a pleasure to pedal away on. Equipped with a 34t replaceable chain ring and a Shimano Deore 12-speed group set, the gear options were plentiful with a full 10-51t range. Shimano’s long lever blades on the installed model mean you may need to move the brake levers inboard to get the best setup, but I found the bar shape, stem reach and lock on grips all a good fit–the ergonomics are really good.

Installed either above ground or inline (underground) Do not use with chemigation May be installed horizontally or vertically, but horizontally is preferred May be installed where the potential for back-siphonage or backpressure is present.

What does RPZ stand for

The XP 919 is for riders who want to get out and ride. Be that exploring rail trails, quick rides to the local trail network, mixed-terrain commutes or even bike packing. Although the frame doesn’t have mounts for racks, the overall design could take some specific luggage really well, and the quality group set will go the distance.

As an alloy hardtail with 2.25” tubed tyres, I did approach the first trails I rode with some trepidation. The balance on the bike was really good though, especially on hard packed rolling flow trails. The Racing Ralph tyres delivered better traction than I expected, and the air-sprung Judy fork helps keep the front wheel tracking. Being accurate with tyre and suspension pressure is key to getting the most out of these components–so invest in a good shock pump and maybe a digital tyre pressure gauge as well.

AVBs are also the least reliable and least often recommended. Most large cities and suburbs do not allow the use of atmospheric vacuum breakers in lawn sprinkler systems. Do not use AVBs in areas of constant pressure. This includes where shutoff valves would be located downstream where there is a potential for back pressure, or on any system that incorporates chemigation techniques.

The first descents I tackled were fairly flowing with some loose over hardpack and very minor features. The XP 919 responded really well to input to pre jump some bigger lips I had no interest in hitting while high-posting, and unweighting over the more pronounced edges that tubed tyres do not get along with well. With as lightly shorter reach than some large sized frames and therefore a slightly longer stem, it is easy to move the bike around at lower to middling trail speeds. At higher speeds on narrow trails a little more attention was needed when coming around corners blind–but the flip side of that is how responsive the bike is to changing lines.

Pressure vacuum breaker assemblies (PVB) are the most common, inexpensive type of whole-system backflow preventer. It consists of an inlet shutoff valve at the bottom, a single valve body consisting of a pressure vacuum breaker, a check valve, two test cocks, and an outlet shutoff valve. As well as being inexpensive, PVBs are relatively simple in design and are easy to install, maintain and repair. Some pressure vacuum breakers also offer built-in freeze protection; however, this only protects the PVB assembly. Inlet and outlet pipes can still freeze if the system isn’t properly winterized.

Rpz meaning plumbing

Reduced pressure zone assemblies (RPZ), also sometimes called a reduced pressure principle assembly, is the most complex and expensive backflow preventer. However, when working properly, RPZs are the most secure and reliable of all backflow prevention devices. A reduced pressure zone assembly consists of an inlet shutoff valve, two independently operating spring-loaded check valves separated by a pressure differential relief valve, four test cocks, and an outlet shutoff valve.

One of the downsides of PVBs is that they will occasionally eject some water. Choose a “spill-resistant” model of PVB for indoor installations or any time spillage would create a nuisance. An air gap drain is also required if the valve is installed in a basement or other interior space.

Reduced Pressure BackflowPreventer Test Procedure

The bike was a cinch to build, and you will only need to navigate fitting the handlebars onto the stem, putting the seat post in the frame and putting the front wheel in. Then you need to setup the cockpit for brake and shifter position, and bar roll, plus set the tyre and suspension pressure–and of course the seat height. I prefer to ride tubeless tyres however the Schwalbe 2.25” Racing Ralph tyres are a basic model that will not support tubeless, however the rim tap fitted may stay airtight if you buy some valves and upgrade the tyres. I fitted my own pedals (platform pedals are included) and put a bottle cage on, and finalised my setup for fit.

Some localities, such as Honolulu, do not allow reduced pressure zone assemblies to be installed below grade in underground lawn sprinkler systems, while others require copper pipes on both ends of the assembly. Local codes may be especially variable and stringent on reduced pressure zone assembly, so have a thorough understanding of local requirements before proceeding.

The Superior Bikes XP 919 arrived via courier at my front gate, or actually in my carport. The courier went straight past the warning sign about a dog being on the property but he got away with it. Like any bike from BikesOnline, the bike you buy will get delivered to your door. This means you need to navigate choosing the model that suits you, sizing, and then building the bike. BikesOnline have a number of online tools to help with all of this, and a robust customer service team you can call as well. There’s even a free returns policy that lasts 30 days–head to their website for the full details.

Zipping up a twisty singletrack climb was a fresh reminder that longer, lower, slacker is not everything. The XP 919 easily navigated the twisty trails with a comfortable pedalling position that kept the front wheel tracking around corners, with no extra muscle needed to bring the front wheel around. With a remote lock out on the handlebars, it was easy to lock the fork for a very smooth fire trail climb or road section as well.

RPZ valve how it works

Reduced pressure zone assemblies come in a variety of configurations. Choose an “inline” or “straight” configuration for installation underground. For above-ground installation, consider an “n” configuration assembly for a very small footprint.

My large test bike has a 69 degree head angle and 74 degree seat angle. This is more modern than my last hardtail and not that far off my current one–although the reach is moderate at 455mm. This does suit a$2000 cross-country hardtail quite well, but more on that later.

Atmospheric vacuum breakers (AVB) are the simplest and least expensive backflow preventers for one or two-zone irrigation systems. An AVB must be installed on the pipe directly after every control valve, so for systems with more than about six control valves, AVBs are not cost-effective.

Where the Superior Bikes XP 919 really shines is in the flowing hardpack trails and multi-use trails. It was fast, with a shifting and braking setup that didn’t miss a beat. The RockShox Judy fork has enough options for adjustment with an air-spring, rebound and lock out to suit riders looking at this type of bike–but the bike nor the fork are the right mix for someone who wants a trail hardtail. BikesOnline can serve that market with something like the Marin San Quentin 2 ($1999) which has 27.5 x 2.6” tyres, a burlier fork and slack geometry.

RRP: $1999 Weight: 12.74kg (as tested) From: bikesonline.com.au Available: Sizes S, M, L (tested), XL Fork: RockShox Judy Silver TK R, 100mm Shifter: Shimano Deore M6100, 12sp Derailleur: ShimanoSLX M7100, 12sp Crank: Shimano FC MT510, 34t, 175mm Bottom bracket: Shimano MT500 BB92 Chain Shimano: Deore M6100, 12sp Cassette: Shimano Deore M6100, 12sp, 10-51 Hubs: Shimano TC500 centrelock Spokes: Black, stainless Rims: Stars J25D, 25mm internal, 32h Tyres: Schwalbe Racing Ralph 29×2.25” Brakes: Shimano MT410, 180/160mm Stem: ONE Race Handlebars: ONE Race, 5mm rise, 760mm Seatpost: ONE Race alloy, 27.2mm Saddle: Fizik Terra Aidon X5

There are multiple types of backflow preventers. The three most common are the pressure vacuum breaker (PVB), the reduced pressure zone (RPZ), and the double check assembly (DCA). These are all installed in the water system immediately after the isolation valve. There is a fourth backflow preventer which is also fairly common. The atmospheric vacuum breaker (AVB) is installed in each zone of the sprinkler system. After that, it immediately follows the zone control valve. Each type of backflow device is designed to provide a different level of protection for varying commercial or residential applications. For example, hospitals and morgues, which handle large quantities of hazardous wastes on a daily basis, require much heavier-duty backflow preventers than a residential irrigation system.