Welcome to Understanding Hydraulics for your swimming pool and spa.
This is the first of 3 videos related to Hydraulics.
The first video will explain
hydraulic terms, how they are used and how they relate to swimming pool
and spa systems.
This video is a general overview of Hydraulics.
The second video will show how the hydraulic footprint for a new swimming
pool is determined.
And the third video will discuss determining the
hydraulic footprint of an existing pool.
In both, we will talk about sizing
equipment correctly and efficiently.
Hydraulics - the bloodlines of a swimming pools pump & filtration system.
A mechanical, pulsating system that cleanses, recycles and reliably
maintains a healthy body and flow of water.
In simple terms, Hydraulics is the study of liquids in motion and at rest.
We
will cover how it relates to water in swimming pools and spas.
Hydraulics, as associated with the movement of water in a pool or spa
takes on many tasks.
Those areas that are affected by hydraulics are:
Filtration: Sand, cartridge and DE.
Heating systems: Gas heaters, heat pumps or solar
Cleaning Systems: Suction, pressure and robotic cleaners.
Spa Jets: Different styles and GPM requirements.
Sanitization Devices: Liquid and tablet feeders, salt chlorination,
ozone and Ultra violet
Water Features: Waterfalls, negative edges, fountains, deck jets
and more.
As the industry grows, there will be more added to this list.
Let’s talk about terms used when talking about hydraulics.
These terms will
be used throughout this and future hydraulic videos.
We will bring these
terms back together with practical application so you can better understand
their use in the vocabulary of hydraulics.
GPM: Gallons per minute
Friction head loss: A factor applied to the resistance of flow through
plumbing, equipment or anything that water flows through in a
swimming pool and spa.
They all have a factor applied dependent on
how fast the water is moving and the size of the pipe.
We will cover
this later in the video.
Friction head loss is also called Head Loss.
System head loss: When we add together all the friction head loss
factors in a swimming pool or spa system we have what is called
System Head Loss or TDH, Total Dynamic Head.
Cavitation: In a swimming pool pump this happens when the pumps
ability to pump all the water it can is hindered by the suction sides
inability to provide the water.
Example; if a pump on the discharge
has the ability to move 100 GPM but the suction side can only
provide 60 GPM you have a pump that cavitates.
The pump trying to
get 100 GPM from the suction side will pull air out of the water
causing bubbles in the pump basket and a noisy pump.
This can
cause damage to the pump if not corrected.
Velocity: The speed at which water is flowing through a pipe,
normally expressed as FPS, feet per second.
Speed is determined
by GPM and Pipe size.
Atmospheric Pressure: Atmospheric pressure on the surface of
water is necessary for a swimming pool centrifugal pump to operate.
At sea level the pressure is 14.7 psi.
As we go up in elevation the
pressure decreases.
A pump that can pull water up 10 feet at sea
level can only do approximately 8 feet at 5000 feet of altitude.
Since we are talking about atmospheric pressure, let’s explain how water
gets from the pool to the pump.
We are going to dispel the notion that
pumps ‘suck’ water.
To have a self-priming pump, it must have two very
important components.
The first being the pump pot in front of the
impeller.
This pot normally has a basket to remove debris before the water
is propelled out by the impeller.
The second is a diffuser that normally fits
over the front of the impeller.
The diffuser helps to break up air and water
during priming, making the impellers job of moving water easier.
When we prime a pump, we fill the pot or basket area with water and place
the pump pot lid on the pump tightly so no air can enter.
When we turn the
pump on, the impeller will move the water out of the pump pot causing a
vacuum inside the pot.
To insure this vacuum happens, all the plumbing
on the suction side of the pump must be airtight.
Vacuums do not like to
exist so water will travel from the suction point (skimmer or drain) at the
pool to the pump pot.
As long as the vacuum exists, the pump will
continue this cycle of pumping water out of the discharge.
It is easier for a
pump to pull water from the skimmer as it will only be a few feet below the
pump.
Pulling water only from a main drain 8-10’ below the pump, for
priming, is not recommended.
The vacuum will stop existing and the pump will lose prime if air enters any
portion of the suction side of the pump.
Pumps lose prime for many
reasons and the most common are:
1.
Water level is too low in the skimmer
2.
The pump pot O-ring that seals the lid goes bad.
3.
A valve on the suction side starts sucking air.
or
4.
A threaded fitting starts sucking air.
Friction Head Loss and all the components in a swimming pool or spa
system can contribute to the resistance of flow.
The following components,
since they have water flowing through them, have a friction head loss
factor.
This factor is dependent on size of pipe and GPM.
Pipes, fittings, return eyeballs, valves, skimmers, main drains, filters,
heaters and cleaners.
There are many more to be added but these
are the most common.
In the second video, we will show how all of this can be used in calculating
the hydraulic footprint of a new pool or existing pool.
Remember to visit Hayward Pool products at hayward.com along with our
social media sites for helpful information about your Hayward products.