Regulator Set

Since it'll all end up being attached together eventually, I'll discuss several items together in this category: a regulator (both first stage and second stages), gauges (pressure and depth, at least), and a BC inflator hose. A dive computer takes the place of a depth guage and bottom timer (see below) for many divers.

first and second stages

Air in a scuba cylinder is at high pressure, and you can't breathe it directly. The job of a regulator is to reduce the high pressure to ambient pressure, which you can breathe. It consists of two main components: a first stage (the piece that attaches to the tank valve), and a second stage (the part that has a mouthpiece), with a hose connecting the two. The first stage has additional outlets, for a backup second stage regulator (so your buddy can share your air if needed), a hose for connecting to your Buouancy Compensator (BCD) so it can be filled directly from the tank, a hose leading to your pressure gauge so you know how much air you have left in your tank, and possibly an additional hose for connecting to a drysuit (you obviously don't need this if you're not using one).

gauge console

These pieces are often sold individually. A regulator in a dive shop usually will come with a first stage and one second stage (for about $200-$400). The backup second stage is an additional expense (maybe $75). These will come with the appropriate hoses for connecting them, and the shop will usually set them up for you (it's not hard to do on your own though).

A hose leading to your BC usually comes with the BC itself when purchased new, although most used BC's (if you purchase one on eBay, for instance) don't include this.

Gauges come in several different configurations. At the very least, you need to have a pressure gauge and a depth gauge. A "bottom timer" (timekeeping device, like a waterproof watch) is also necessary for timing your dive. Many dive computers combine several of these features into one unit, keeping track of depth, total dive time, dive time remaining, (and occasionally tank pressure) simultaneously. All of these devices are often mounted in a rubber housing, or "console" that lets you keep them all in one place (though somve divers wear at least some of these gauges on their wrists). A new console with simple depth and pressure gauges may cost $100-$150 retail. Many include a compass also (which allows you to navigate underwater) for an additional cost.

Rather than a simple set of pressure and depth gauges, many divers choose to buy a dive computer instead. Dive computers differ in their features, but most replace a depth gauge and bottom timer, and keep track of your theoretical nitrogen accumulation while you're diving. This means all of the calculations divers learn about using dive tables are done by the computer instead, which often offers more allowable dive time, since it doesn't make the shortcut assumptions of dive tables (regarding maximum depth, etc). Computers often add other features as well: many also replace your pressure gauge (giving you a digital readout of your tank pressure), tell you the time, water temperature, and record all of this information for retrieval later, either through the dive computer's readout, or by downloading the data to a personal computer later. Many computers are also customizable for use with breathing gases other than air, such as "enriched air"/nitrox, which allows a longer dive time under certain conditions. Many divers like using dive computers, and are willing to pay more for the privilege: they may cost several hundred dollars more than a basic set of gauges.

Regulators are "life-support equipment", and need to be inspected and maintaned regularly: the dive industry suggests annual maintenance for this equipment, which any dive shop is happy to do, with a typical service cost of ~$50-$100. Some manufacturers offer free replacement parts with each service (depending on the manufacturer) if you've bought your regulator from an authorized dealer (ask about this before buying one). It isn't really feasible to service your own regulators, since they are somewhat complex inside (it's easy to damage stuff if you don't know what you're doing), and no one will sell you the replacement parts directly anyway.

Next page: Choosing a Scuba Cylinder