In-Ground Pool Anatomy

In-Ground Pool Anatomy

An In-Ground Pool Anatomy

Here is a drawing of a basic in-ground pool set up. This illustrates the places where water comes in and out of your pool. Water is sucked in through the skimmer(s) and the main drain(s), pumped through your filter, and then back into your pool through the return lines.

Note: This is not how EVERY in-ground pool is set up, but the logic works the same way. Every pool has a skimmer to suck in the water into and through the filter, and every pool has a return line to push the water back into the pool.

The Suction-Side Of Your Pool


These are buckets, built into the concrete, that house a skimmer basket (hence the term, skimmer). Skimmers are what suck the water out of the pool and through your filter system. They should have a small plastic basket inside to catch any large debris including leaves, sticks, and bugs before it enters your pump (which also has a basket).

Main Drain

This is another place where water is sucked in and pushed through your filter. Main drains are usually located at the bottom of the deep end of the pool. While the skimmers take care of pulling water off the top of the pool, main drains are great for pulling water off the bottom. That way, you are pulling water from all areas of the swimming pool.

Note: Older in-ground swimming pools probably won’t have two main drains. The reason why newer pools have two is for safety. When you have two, it splits the suction in case something or someone blocks one of the drains.

The Pressure-Side Of Your Pool

Return Jets

This is the jet that pushes the water back into your swimming pool after it’s been filtered. The jets also help to push or circulate the water around, allowing the skimmers a better chance to pick up more debris.

Tip: If you have two or more return jets in your pool, angle some of them down towards the floor and in one direction, either left or right. You want to create a circular motion while helping to kick debris off the bottom with the jets angling down.

Note: If you have jets in your steps, these are also return lines.

Your Filtration System

Your filter system should be made up of two parts, the pump and the filter. Often, owners will refer to these as one unit, but they are completely different. Your pump is what moves the water and the filter is what…well…filters it or cleans the water.

The Pump

This is the unit that draws in the water from the pool, pushes it through the filter and back into your pool. It consists of two parts. The pump, which technically is the bucket with a lid and a basket inside. There is also an impeller that spins super fast. That’s what sucks the water in and out.

The other part is the motor. The motor is the heavy long tube shape piece behind the bucket with the lid. Its job is to spin that impeller and spin it fast. Pumps come in all shapes, sizes and speeds. The speed is what’s really important. It’s measured in Horsepower and it ranges from ¾ horsepower to 3 horsepower, on average.

Smaller pools don’t require as much horsepower as a larger pool. So, the bigger the pool, the bigger the pump and motor.

The Filter

Once the pump has sucked the water in, it immediately pushes out into your filter. You filter cleans out the water of fine debris and then it moves back into your swimming pool. There are three types of filters to clean your swimming pool, sand, D.E.(diatomaceous earth) and cartridge. They all filter out tiny particles from your pool water.

Sand Filters are the most common and least expensive type of filters. As water passes through the filter, a bed of silica sand traps and removes particles from a pressurized water stream. Sand filters are cleaned by a reverse upward flow of water called backwashing. The backwash process extends the life of the bed, as the finer sand removes the larger particles. Sand filters typically remove particles down to the 25-30 micron size range. Sand filters should be cleaned 2-3 time per season, in addition to backwashing, and the sand should be replaced every 3-5 years. Premier Pool & Spa has Silica sand available.

Cartridge Filters utilize a woven mesh fabric that is wound around a cylindrical structure. Water passes through the cartridge, where the woven fabric removes particles from the water. Cartridge filters exhibit superior filtration performance relative to sand, as they can generally remove particles down to the 10-15 micron range. The lifespan for filter cartridges lasts between 1-3 years. Most manufacturers recommend a rotation of cartridges to fully extend their lives. You will have a spare that you install while cleaning a dirty filter. Once cleaned, the filter can then dry where the fibers of the fabric will tighten up, allowing them to be stronger upon subsequent filtration. Small particles and oils are very difficult to remove but Premier Pool & Spa does have a filter cleaning service available.

D.E. (Diatomaceous Earth Filters are comprised of a tank that holds rigid structures, called grids or elements where the filtration takes place. Filtration occurs at the grid surface. D.E. powder (fossilized remains of of algae called diatoms. These fossilized exoskeletons are very porous which gices them significant filtration capacity). It is the filter cake that removes the particles from the water, not the fabric or the grid itself. D.E is considedred to be the most efficient filtration and will remove particles 1-3 microns in size. To clean D.E. filters the powder is washed out with the debris and must be replaced after backwashing. Backwashing should be done when filter pressure rises 10-15 psi above normal operating pressure. Premier Pool & Spa has D.E powder available.

Extra Equipment

What we just talked about are the main ingredients to a functioning swimming pool, but you can always add more the party.

A Heater

I think this goes without saying, but yes, a heater heats up your pool water. It’s a nice feature to have on your swimming pool and you can get it on both above ground and in-ground pools. There are a few types of pool heaters including natural gas, propane, electric and solar. Although it’s not a necessary piece of equipment when it comes to circulation and cleaning your pool, it’s just awful nice to have.

A Chemical Feeder

Chemical FeederThis handy little piece of equipment makes adding pool sanitizer to your pool easy. Just fill it full of the correct sanitizer (i.e. chlorine, bromine or a mineral cartridge) and let her rip. This is the last piece of equipment in your filtration line. The order of equipment is as follows:

  • Pump
  • Filter
  • Heater
  • Chemical Feeder

You don’t want to add the chemical feeder before a heater because the water coming out of the feeder has got a bunch of chemicals in it and will take a toll of the inside of a heater over time.