What are pressure drop and volume drop?

What is pressure drop? And does it have anything to volume drop?

Estimated time to read: 3 minutes

March 10, 2023

What is pressure drop?

Pressure drop … It just sounds bad, doesn’t it? “Eat your vegetables kids, or you’ll get pressure drop!” And to be truthful, pressure drop isn’t particularly good, but it is quite easy to understand and simple to monitor. It’s basically the reduction in pressure between two points. These two points are usually the point that compressed air leaves your air compressor and the point in your system where it is used. This means that the pressure drop occurs as the compressed air travels through hoses or pipes.

There are a few reasons why the pressure drops. As the compressed air presses against the inner walls of your hose or pipe, it creates friction. This friction slows the compressed air down. As it slows down, the compressed air loses pressure. Voila! Pressure drop!

How do you stop pressure drop?

The more your compressed air presses against the walls of the hose or pipe, the more the pressure drops. There will be more air pressing against the wall if you have a pipe or hose with a smaller diameter. As such, there’s less friction on a hose or pipe with a higher diameter. Pressure drop is also caused by connections and elbow turns in your pipeline. The more connections and turns, the more the pressure drops. A pipe or hose that runs in a straight line will have less pressure drop. Pretty easy to understand, right?

Finally, obstructions in the pipe or hose will result in the pressure dropping. Obstructions? Rust, grooves and scratches are the usual suspects, but the inside of your pipeline or hose might have sticky, viscous oil stuck to the inside of it too. The compressed air will have a difficult time with this. For the same reasons, the smooth, polished metal inner surface of a pipe will result in less friction and less of a drop in pressure than the gummy, sticky and inconsistent inner walls of a rubber hose.

What is volume drop?

Volume drop is caused when air is lost - or leaks from your compressed air network. The air escapes, and so the volume of air drops. Makes complete sense. It usually happens when there are bad welds or poorly pressed joints in your system. You might have poor-quality fittings or gaskets or they might be worn out. A certain amount of volume drop is kind of inevitable. You should aim for a maximum of 10% of the compressor station performance. If it’s more than this, you’ll need to find out where the leak is. Fix, repair or minimise it to the best extent possible. 

What happens when you have pressure drop or volume drop?

The more the pressure drops and the more the volume drops, the harder your compressor has to work. As you know, if your machines are working harder, they’re working less efficiently. They use more power and need maintenance and servicing far sooner and far more frequently.

Our advice? Always take the potential for drops in pressure and volume into account when you design your system. Aim to have pipes running in straight lines. The fewer elbows and joints between pipes, the less likelihood for problems. And as a special bonus, you’ll have fewer checks to perform on your maintenance rounds.  

Got questions? Worried about pressure drop or volume drop? Get in touch with us at ALUP. We are always happy to help.

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Pressure drop is usually defines as the pressure drop in the distribution grid between the compressor and the appliance. The main factor that affects the amount of pressure drop is the gauge of the pipe. The smaller the pipe gauge, the greater the friction is and the greater the pressure drop is. The size of the pressure drop should be taken into consideration when designing a pipeline dimension. It is important to find balance between piping gauge so that pressure drop is minimal.

Reducing pressure and volume drop can bring financial savings to your compressed air system. Considering the fact that up to 30% of the cost to generate compressed air in a system can be attributed to leakage means higher electricity costs, it is necessary to be careful when considering the choice of not only the pipeline dimension but also of the material and overall design of the distribution grid.

See below table for typical leakage costs 

Hole Diameter (mm)

Air Leakage @ 7Bar(g)

Power to Air Leaks(kW)¹

Cost of Leak (£/Year)²


Cubic feet minute

48 hrs/week³

120 hrs/week³


























¹ Based on 300W/litre  ²Based on 15p/kWh  ³Based on 50 weeks operation per year operation


Source The Carbon Trust