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How Does a Pool Pump/Filter System Work?

sistema filtracion piscina

Learning about pools takes time. It’s even worse when you can’t pick the equipment needed for a pool. But we’re here to make your life easier, in every way we can. So today… let’s talk filter systems.

Heads up: At Neptune Pools, we manufacture and install fiberglass pools only. However, this filter system guide applies to all three pool types.

how a pool filtration system works


Your pump pulls the pool water from the skimmer(s) on the pool wall and the main drain(s) on or near the bottom of the pool.

The water flows through the pump to the filter, which removes dirt, debris, and (if the filter is good) bacteria.

After the water is filtered, it flows through the plumbing to the heater (if you have one) and then the salt chlorine generator (if you have a saltwater pool).

The clean water returns to the pool through the return jets on the pool walls.

Check out this great video tutorial

Thanks to Jason Hughes YouTube Channel

The Skimmer and Main Drain

These features are probably already familiar to you, but just to recap.

A skimmer is the rectangular opening at the top of the pool wall, right below the coping. (The water level should generally be about halfway to two-thirds up the skimmer.)

The main drain is the big ol’ drain at the bottom of the pool.

Side note: You may not have the main drain—they’re becoming less common in residential pools, in favor of only skimmers. This is because, for smaller pools, main drains aren’t always necessary. At Neptune Pools we do not install them, they are not necessary, they are an additional expense and go against saving water.

Water flows through the skimmer and the main drain towards the pump and filter to be cleaned.

The Pool Pump

A pool pump generally has a big, round part at the front and then extends backward.

bomba piscina panama

That big, rounded part at the front (covered by a lid) is the strainer pot. It looks and acts, predictably, like a strainer.

A spinning impeller inside the pump pulls the water in from the pool.

This water hits the first part of the pump, the strainer pot, which catches any major debris.

After the water goes through the strainer pot, the impeller pushes it onto the filter.

The Pool Filter

All pool filters fall in one of these three categories:

  • Cartridge filter
  • Sand filter
  • Diatomaceous earth (D.E.) filter

A cartridge filter uses cartridges—big sheets of polyester cloth or paper folded accordion-style—to catch debris. Some of these filters only need a single cartridge; others need multiple.

(Here at Neptune Pools, most of our customers get a sand filter with their fiberglass pool.)

swimming pool cartridge filters

A sand filter is straight-up a tank full of sand. Slotted lateral pipes at the bottom disperse water evenly through the sand to catch debris.

Diatomaceous earth filters use 8–10 filter grids/fingers covered in D.E. powder (diatomaceous earth, which is basically fossil dust) to catch debris. The fingers may look like hanging stalactites or overlapping curved shutters, depending on the model.

diatomeas filter

A quick note about filter quality!

Dirt and debris are measured in microns, which is short for micrometer—one-millionth of a meter. Yes, that’s a lot of zeros.

For reference:

  • 1 millimeter: 1,000 microns
  • Human hair: 50–100 microns
  • Pollen: 30 microns
  • Household dust: 4 microns
  • Bacteria: 2 microns

A filter’s “micron level” tells you the size of the smallest debris it catches, so a lower micron level means better filtration.

The Pool Heater

Pretty much all pool heaters are one of these three types:

Electric heat pumps
Solar heaters
Natural gas/propane heaters

(Solar heaters usually look like solar panels and are outside the scope of basic pump/filter system plumbing. For our purposes today, we’re talking heat pumps and natural gas/propane heaters.)

The Salt Chlorine Generator

Heads-up: If you don’t have a traditional chlorine system in your pool or you are not going to install one, you don’t have to worry about this section.

For a saltwater pool, instead of adding chlorine to the pool water, you add salt, and the generator converts it to chlorine.

(It’s about as salty as a teardrop, nowhere near ocean levels.)

The salt chlorine generator has multiple parts:

  • The cell
  • The control board

The cell is what’s connected to the plumbing pipes. The control panel is usually a little farther away.

clorinador de sal

After being filtered, your pool water flows through the cell. Inside, a series of metallic grids with a low-voltage current creates a reaction that converts the salt down to little bubbles of pure chlorine. This pure chlorine reacts with the water to form hypochlorous acid, which is what cleans your pool.

Cool, right?

The Return Jets

Return jets… well, they return the filtered water to the pool.

Spa jets are a variant of this.

return jets retorno

I’m trying to think of a way to make it more complicated, but it’s not.

Want to learn more about pools?

I mean, you’re basically a pool pro now. But it never hurts to expand your repertoire!

Our blog articles answer every question you may have about pools, throughout both the buying process and lifetime ownership. Check them out, and then impress your friends and family with your pool knowledge!

Based in Chame and Panama City, PTY, Neptune Pools specializes in manufacturing and installing fiberglass pools because we’re firm believers in their long-term quality—they’re beautiful and durable, require little maintenance, and have a quick installation time to boot.

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