A common question asked by new sidemount divers is what hose lengths are needed. While at first glance this appears like a simple question there are some things to consider when choosing the correct hose lengths for your new rig. Hose lengths will depend on the types of first stages and second stages you will use with your sidemount rig, how you want to route your hoses, and the type of sidemount diving you plan on doing.
Here’s a list of standard hose lengths you will want to consider. You will need two of each.
Low pressure regulator hoses – 5′ or 7′ if you decide to use a long hose, 15- to 34-inch depending on how you plan on routing short hoses.
Low pressure inflator hoses – 12- to 15-inches long, most common length is 15-inches. (Only one needed if you do not dive in a dry suit.)
High pressure hoses – 6- to 9-inches long.
Let’s look at your first stages and second stages first. Some regulators are better suited to certain positions and hose routings than others. Diaphragm first stages similar to the HOG or Dive Rite models work well in any position. They do work better in some positions because of the angle of the high pressure ports. Piston first stages similar to Scubapro and Atomic Aquatic models tend to work better in certain positions. Make sure you discuss the differences with your instructor or mentor.
You will need to decide whether you want to use a long hose with your set up. If you plan on diving with others and want to be able to donate air, a long hose is recommended. While there are some that advocate trading cylinders in an out of air situation, that is not practical. A long hose is a better option. If you plan on diving smaller passages in which you and your team members must pass in single file, you should consider a 7′ hose as a 5′ hose will not be long enough to allow single file exits.
The more difficult hose lengths to determine are the short hoses. Lengths depend on how you plan on routing the hoses. The options are to route them directly from the first stage to second stage or around the neck. Some second stage regulators can also have the hose come off of either side. This will also have an effect on the hose length. Finally, if you use rotating or fixed angle swivels, you will be able to shorten your hose length by another inch. For hoses that route directly to your mouth, you will need 15- to 22-inch long hoses. The exact length depends on the options just discussed. For hoses that you will route around your neck, you will need 31- to 34-inch long hoses.
The low pressure inflator hose lengths are largely dependent on 1st stage regulator type and which port you choose to use for the inflator hose. As state previously, the most common hose length is 15-inches. This length works well with standards first stages and most any low pressure port. If you have first stages with low pressure ports located on the end of the regulator you will be able to use a 12-inch long hose however I don’t recommend this. This tends to put undue stress on the internal o-ring of the low pressure inflator hose and it will significantly shorten its life. I tried using shorter hoses and ended up replacing hoses every 6 months or so. With the longer hoses I can go a couple of years of longer with no issues.
The most common high pressure hose length is 6-inches. This length works well with the SPG positioned in any direction. The 9-inch long hose allows for the SPG to be pulled back a little farther from your face if that is necessary for reading the gauge. It also works better when positioning the SPGs down alongside the cylinders.
If you have a large stock of hoses at home (like many of us do after several years of diving), be sure to bring all the hoses you have in the range listed above. This may save you some money, and room in your dive storage locker, when setting up your sidemount regulators. Make sure you discuss the different options with your sidemount instructor or mentor.