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National Association of
Underwater Instructors
"Outstanding Service Award" - 2015




Adaptive Diving Association


SCUBA Equipment Services Available at Hilltop-Diving: We offer a full range of SCUBA and skin diving services and instruction. Our service and repair department utilizes state-of-the-art testing equipment and the latest in specialty tools to keep your equipment functioning flawlessly. We use ONLY oxygen-compatible cleaning solutions and lubricants in our test facilities.

We are highly trained in the service and repair of the latest technologies and in a wide variety of older models as well. Don't trust your life support equipment maintenance to just anyone!

We are confident our quality and service will meet and exceed all of your expectations.




Though it is not as diverse or colorful as the wet suit, the SCUBA tank, or diving cylinder, is arguably the most important piece of SCUBA gear any diver uses. A working SCUBA tank is full and ready for the next dive. As such, many divers wonder about the details and process of refilling their tanks, either themselves or through professional assistance. Divers should understand air compressors and how to use them to refill a tank.

Understanding SCUBA Air Compressors:
The only way to properly and safely refill a SCUBA tank is with a specially-formulated SCUBA air compressor. These large, complex pieces of equipment allow divers to fill their dive tanks to an average of 3,000 psi safely. They are quite different from regular air compressors in this regard and have a specific way of working.

SCUBA Air Compressor vs. Regular Air Compressor:
The high pressure most SCUBA tanks hold allows divers to carry much more air with them on a dive, and thus stay underwater for longer periods of time. Most normal air compressors cannot fill a tank to 3,000 psi. Another important point that differentiates a SCUBA compressor from standard compressors is a built-in filter that purifies the air put into the tank. This filtration process eliminates water, oil, and other contaminants commonly found in the air, thus making it safer to breathe as well as store at high pressure.

How SCUBA Air Compressors Work:
The way that a SCUBA air compressor draws atmospheric air and fills it into a diving cylinder is not unlike the regular process of any air compressor. It draws air in and compresses it, usually to about 100 to 140 psi in its initial stage. However, unlike a standard air compressor, which then lets that air out through a tubing system, SCUBA air compressors cool the compressed air and then cycle it through their system again, usually reaching 800 to 1,000 psi on the second pass. The compressor then repeats the cooling and compressing process once more to get the air up to 5,000 psi before filtering it and using a back pressure valve to release it at a rate of 2,700 to 3,300 psi.

Using a SCUBA Air Compressor to Refill a SCUBA Tank:
The unique system of a SCUBA air compressor means that it is the only way to refill a SCUBA tank safely and effectively. Users who own a SCUBA compressor or who have access to one must further follow a precise set of instructions to refill the tank with the SCUBA compressor. This includes considering the limitations of their diving cylinder as well as operating the compressor machine in the proper way.

Knowing the SCUBA Tank's Capacity:
The type of SCUBA tank that a diver owns dictates the amount and type of air and compression level (psi) that divers can use to refill it. Divers should be aware of this information before refilling a tank. The table below outlines common tank types with important information about refilling them.

Knowing the maximum of pressure of the SCUBA tank is essential when refilling it. Not doing so leads to a risk overfilling the tank and, possibly, an explosion of compressed air as a result. Divers should always be careful when refilling a tank.

Refilling the SCUBA Tank:
Once divers are confident regarding the limitations and requirements of their SCUBA tank, they are ready to refill it using the SCUBA air compressor. There are seven basic steps to this process.

First, divers should recheck the cylinder for safety including noting its hydrostatic testing date. Second, they can open the bleed valve on the side of the chamber to empty the cylinder to 10 psi. Third, set the controls on the compressor to automatically shut down when the maximum psi for the cylinder occurs. Fourth, place the cylinder into the air compressor's water tank. Fifth, close the bleed valve and attach the valve yolk to the nozzle on the top and tighten it. Sixth, open the bleed valve and the compressor yolk valve and start the compressor. Finally, once the tank is full, divers should close both valves and disconnect the yolk.





Controlled by the U.S. Department of Transportation:
Pressure vessels are regulated by the DOT for the safety of transport vehicles, their passengers and the environments through which they pass. Every scuba tank model must pass an initial DOT certification, then EACH manufactured scuba tank must pass a test before it can be sold. It is somewhat equivalent to space specifications, so this is an extremely well-controlled industry!

Hydrostatic testing:
After the initial test, the results are stamped into the body of the scuba tank, along with the date (year and month) it passed. After that, the tank must be retested hydrostatically every five years. The test for each tank is on file at the DOT, and the testing station must contact them to obtain the correct test specification. A common hydrostatic test is to pressurize the scuba tank to 5/3 of its working pressure and to measure the flexing of the tank walls. Five-thirds of a 3,000 psi working pressure means that the tank will be pressurized to 5,000 psi. This is done by replacing the valve with a special hydraulic testing connection and filling the scuba tank with water under pressure – NOT air! Air would be too explosive if the tank were to let go during the test, as it sometimes will. Because water cannot be compressed, the tank cannot explode if it fails. Testing is done inside an armored containment vessel. The tank is also under water, and they measure the amount that a water column rises as the tank is pressurized. This measures the amount of tank expansion. The water inside does not expand, but the aluminum or steel tank casing certainly does! They are looking for tanks that DO NOT expand as much under pressure, indicating that their walls have been work-hardened over the years. Like a piece of steel that is repeatedly flexed, the tank walls get hard to the point that they may suddenly fail with a snap. This is EXTREMELY rare outside the testing station. When it DOES happen, it’s almost always fatal to people standing close by.

You know it when they fail:
When a tank fails during hydro, it’s usually the valve threads that let go. It sounds like a loud “whump” if you are in the building when one fails. The other thing that sometimes happens, but not as often, is that the bottom of the tank bursts open. This is due to corrosion. If the tank fails to flex enough during the test, it can never be filled with air again, and no dive shop will do so. It will not be stamped with a current test stamp (one within the past five years) and is “out of hydro” as far as any dive shop is concerned. One possible use for a failed tank is to cut off the bottom with a carbide saw (a lengthy process!) and hang it far downrange on a rifle range to be used as a gong.

The annual visual inspection:
The annual visual inspection is performed by a dive shop. They let the air out of the tank and removes the valve to have a look inside. They’re looking for signs of corrosion and will refuse to put a visual inspection sticker on the tank if they find any. These stickers are paper or plastic and they stick to the tank. Every dive shop I have used has refused to fill a tank that has an out-of date inspection sticker. But they can do the inspection right there – the tank does not have to be sent to an outside party. They open the valve a little to slowly let the air out. This prevents condensation from rapid cooling. It takes 12 hours or more for a tank to bleed down – especially since airgunners seldom let their tanks drop below 2,000 psi. Let the dive shop bleed your tank for you; they know what they’re doing!





We invite you to focus on the fact that Diving or Snorkeling is an AWESOME visual experience! If you need optical correction on land, in order to see clearly underwater and enjoy the best possible adventure, take advantage of our ‘Custom Lens Masks’. Whether you are viewing beautiful coral reefs or tropical underwater landscapes, a custom lens mask will be an essential piece of your equipment.

A poorly fitting mask that leaks or is uncomfortable can ruin a dive. A mask which fits in the store may not fit under all diving conditions. Sometimes style, quality, and features must be sacrificed for a mask with proper fit and comfort.

Whether you are snorkeling or scuba diving, there are a few basic things to remember when selecting and preparing a mask for your next snorkeling or scuba diving adventure. The reason you are shopping for a mask is so you can enjoy the awesome beauty and serenity of the underwater world. If your mask is uncomfortable or leaks constantly, an otherwise wonderful experience can be ruined. Scuba divers should look for the largest field of vision a mask has to offer with the lowest internal volume so that the mask is easier to clear. Snorkelers should look first for fit and comfort, then consider style and color. How do you know what to look for when fitting a mask? Ask one of our highly trained staff, we would be happy to help.




Scuba divers are guests in a foreign world and thanks to the ability to alter or manufacture scuba equipment, it’s a world that is open to everyone. Through 'Adaptive Diving Association' and 'Hilltop-Diving', our instructors are able to help people with disabilities enjoy the sport of scuba diving. 'Hilltop-Diving' has helped people of all types enjoy the sport over (30) years, helping ensure those interested in the sport can find the right equipment.

Scuba diving is a fascinating pastime. By going underwater for extended periods of time, divers are able to explore marine life up close. The sport provides participants with not only fantastic exercise, but a social community that extends far beyond the dive.

Our specialty is tending to the individual needs of the (prospective) diver who needs adaptive training including those who are wheelchair-bound. This includes specialized training, custom fabricated assistive equipment and under-water video taping for self-evaluation.

If there is any question as to whether you could possibly be fitted for a diving experience, checkout the testimony and video below:

In 2014, Jim experienced one of his most unique, memorable encounters. During an adaptive diving event for the Carousel House (a year-round recreational and social center for disabled individuals), he trained quadruple amputee Christine Kaestle, who exhibited an intense, indomitable drive for learning adaptive diving.

"Christine's Experience" Video, Courtesy of Cigna Insurance ...

Weeks later, Jim received a call from the Cigna Health Insurance, who were producing a documentary on Christine’s experiences; she recommended Jim take part in this valuable video. The company asked Jim to completely train her in scuba diving over a span of one week: a challenging task given the timeframe, but not impossible for a teacher like Jim, and for a student as determined as Christine.

“She showed up at the pool, and we helped her in. This lady could teach the Energizer Bunny new tricks: she has an unbelievable personality and an incredible energy. I manufactured her arm fins, and one week later she was on independent scuba. When she came out of the pool, she was grinning from ear to ear!”





There’s a world of underwater adventures out there waiting for you. Scuba diving and traveling go hand-in-hand. Your next dive trip experience could lead you to your new favorite dive site, best wreck dive, most memorable wall dive or give you the chance to capture that perfect shot of some of nature’s greatest and most colorful creations.

‘Hilltop Diving’ has the expert information you need to plan a great dive vacation. Whether you’re interested in a long weekend at a nearby resort, or traveling to an exotic destination for an extended trip, there are plenty of options to choose from.

You can join a group trip or book an independent holiday. ‘Hilltop Diving’ can help make your dive dreams come true. Pick a destination and pack your bags. Call us now (610) 287-7270 and start planning your vacation of a life-time!


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Hilltop-Diving
55 Pennypacker Road
Schwenksville, PA. 19473
Phone: 610.287.7270
   Fax: 610.287.0806

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