In follow up from my post “Should I dive with an unbalanced regulator?” I thought it would be worth discussing the overbalanced regulators, the other end of the scale so to speak. We get a lot of enquiries about overbalanced regulators, this post is to discuss the pros and cons of using this style of regulator.
Essentially an overbalanced regulator is a first stage with a different style of diaphragm which allows the interstage pressure in the hose to increase faster than a traditional balanced regulator at depth. The increased interstage pressure compensates for the increased density of the air at depth allowing larger volumes of air to pass through to you; the diver. In simple terms it allows more air out of the first stage at depth giving you better breathing performance, regardless of depth. Like balanced regulators, overbalanced regulators will not decrease in performance as your tank pressure decreases but will give you excellent performance pretty much up the moment your tank runs out.
Because of the increased interstage pressure at depth an overbalanced first stage can (although it’s very unlikely) make second stages more prone to free flowing. A way to stop this is issue is to de-tune the second stage which would stop the likelihood of free flowing, but it would also increase the inhalation effort at all depths, which takes away the advantages of an overbalanced first stage. Some modern second stages which generally speaking come paired with an overbalanced first stage have a flow adjustment knob or switch on them to resolve this issue. To explain how this works (in simple terms), essentially as you wind the adjustment in more pressure is put on the spring that stops the air flow and makes it harder to breathe (but less likely to free flow) as you wind the spring out the pressure on the spring lessens, making the breathe easier but more likely to free flow. The idea of this adjustment being that you start your dive with the regulator adjustment set to make the inhalation effort to be quite hard (but it won’t free flow) then as you dive down you wind the regulator out to get a better breathe. At depth regulators are less likely to free flow due to the pressure difference. This allows technical divers to get the advantages of an overbalanced regulator without the issues of free flow.
Unless you are diving to great depths or diving with denser gas like Nitrox then no you don’t “need” an overbalanced regulator. A normal balanced regulator will be more than sufficient and will still provide a fantastic breathe, however that said there is no reason why you shouldn’t go for an overbalanced regulator at all.
We have a lot of different overbalanced regulators in stock, we would personally recommend any of the following: