Top 4 Techie Terms Decoded on Pool Hydraulics

Pool Pros have the very important job of understanding how your pool’s system works, and how to make it efficient and effective.  Some of the more technical terms can be confusing, let’s break them down into easily understood terms.


Head Loss in pipes, it is defined as pressure loss due to friction. We actually prefer the term Resistance to Flow.  It’s quite simple, and not a good thing.  A Pool Pro’s job is to reduce head loss in your swimming pool’s plumbing, so that your filtration system does its job well and energy efficiently.

System Head Loss    When you add up all the system head loss factors (filter, heater, pipe, etc.), you have the total system head loss which is also called Total Dynamic Head or (TDH).

Gallons per Minute (GPM)  The flow generated by the pump is typically measured in gallons per minutes or GPM.  As the system head loss increases, the flow decreases, which means your pump has to work harder and will ultimately consume more energy.

Velocity is the most important factor in a pool’s healthy hydraulics. It’s the speed at which water flows through a system.   Velocity is measured as Feet per Second (FPS). This is very important because as the velocity increases, so does the head loss.

Why do we Care?  Pool Pros use the information above to determine the right pump, and other equipment, for each unique pool system.  We view a swimming pool or spa’s hydraulic footprint like we do fingerprints – every system is unique.  This is why Hayward recommends you always have a Pool Professional recommend equipment for your pool.

Check out our dealer/servicer locator to find a local Pool Pro in your area.