How Your Pool Plumbing Works — Follow the Water

Ever wonder what happens when your pool pump kicks on? Water doesn't just magically get clean. It travels a specific path through your plumbing system, getting filtered, treated, heated, and sanitized before returning to your pool. Here's exactly how it works.

 

The Two Sides of Your Pool Plumbing

Your pool plumbing is divided into two sides: the suction side (where water is pulled toward the pump) and the return side (where treated water is pushed back to the pool).

Step 1: The Main Drain Pulls From the Bottom

Your main drain draws water from the pool floor, circulating the entire water column and preventing dead spots where algae can grow. It feeds directly into the suction side of the system.

Step 2: The Skimmers Pull From the Surface

Two skimmers on the right wall, one near the top and one near the bottom, pull water from the surface at the waterline, catching leaves, bugs, and floating debris before they sink. Their baskets should be emptied regularly to keep water flowing smoothly.

Step 3: The Pump Moves Everything

Your variable speed pump is the heart of the system. It creates the suction that pulls water in and the pressure that pushes it through the rest of the equipment. Running your pump at the right speed and duration is key to energy efficiency and water quality. Still running an old single-speed pump? A variable speed pump can cut pump energy use dramatically.

Step 4: The Filter Cleans the Water

Water passes through your filter (sand, cartridge, or diatomaceous earth/DE), which captures fine particles, dirt, and debris that you can't see with the naked eye.

Step 5: UV / Ozone Supercharges Sanitizing

Next, water flows through a UV / ozone system, which combines ultraviolet light (UV-C) and ozone to create hydroxyl radicals. Together they form a powerful Advanced Oxidation Process (AOP) that rapidly destroys organic debris, bacteria, and viruses in milliseconds.

It also breaks down chloramines (chlorine combined with sweat or oils), eliminating that sharp chemical pool smell and stopping eye, skin, and hair irritation. It achieves a 99.9% reduction in stubborn waterborne bacteria like Pseudomonas aeruginosa and Enterococcus faecium, and because it handles the heavy sanitizing, you can maintain a much lower chlorine level in your pool.

Step 6: The Heater Warms It Up

If your pool has a heater, water passes through it briefly to reach your desired temperature. Gas heaters and heat pumps both work in-line with the plumbing system.

Step 7: Chlorine Dispenser or Salt Cell Sanitizes

Your chlorine dispenser or salt cell adds the right amount of sanitizer to kill bacteria and algae. An automatic chlorinator slowly dissolves 3" chlorine tablets, while a salt cell turns dissolved pool salt into chlorine. Thanks to UV / ozone upstream, you'll typically need less chlorine to keep water safe.

Step 8: Return Jets Push Water Back

Clean, treated water flows back into the pool through two return jets on the left wall, one near the top and one near the bottom. Spacing them out creates strong circulation that distributes chemicals evenly and keeps every corner of your pool clean.

Pool and Spa Lighting

Pool and spa lights make evening swims easier to see and enjoy. They also highlight your pool's design and add a warm glow to your backyard after dark.

Bonus: Automation Gives You Total Control

An automation system isn't part of the water path. It's the brain that ties everything together and gives you total control of your backyard experience. It can connect with your home automation system, and seasonal scheduling automatically adjusts run times throughout the year for additional energy savings.

• Control individual pool and spa functions, lighting, and water features from the comfort of your home
• Automate daily equipment functions like filtration, sanitation, and cleaning, and create one-touch routines
• Integrate seamlessly with home automation systems
• Control your equipment anytime, anywhere from a smartphone or tablet app
• Program your preferred settings and run them with one-touch control

Signs Your Plumbing Needs Attention

Your system usually tells you when something's off. Watch for these warning signs:

• Loud or grinding pump: often worn bearings or the pump running dry.
• Pump losing prime or air bubbles in the pump basket: usually an air leak on the suction side or low water level.
• Filter pressure 8–10 PSI above normal: time to clean or backwash the filter.
• Weak flow from the return jets: clogged skimmer or pump baskets, a dirty filter, or a blockage in the lines.
• Cloudy or green water despite normal chemical levels: poor circulation or a filter that isn't doing its job.
• Wet spots or puddles around the equipment pad: a leak that should be fixed before it gets worse.

Keep your water balanced in between service visits with a reliable test kit and the basics like pH Up, pH Down, Alkalinity Up, and pool shock.

Frequently Asked Questions

How long should my pool pump run each day?

Most pools need enough run time to turn over the full volume of water at least once a day, typically 8–12 hours in summer and less in cooler months. A variable speed pump can run longer at low speed for better filtration and lower energy bills.

How often should I clean my filter?

Clean or backwash when the pressure gauge reads 8–10 PSI above its clean starting pressure. For most pools that's every 4–6 weeks during swim season, and more often after storms or heavy use.

Why is my pump running but the water isn't moving?

The pump has likely lost prime. Check that the water level is at mid-skimmer, empty the skimmer and pump baskets, and make sure the pump lid is sealed tight. If it still won't catch, there may be an air leak on the suction side.

Do I still need chlorine with a UV / ozone system?

Yes, but much less. UV / ozone handles most of the heavy sanitizing inside the equipment, while a small chlorine residual keeps protecting the water in the pool itself.

Need Help With Your Pool System?

Calaveras Pool Service handles everything from routine maintenance to equipment repairs and upgrades, including variable speed pumps, UV and ozone systems, salt systems, and pool automation. Serving Calaveras County and the Sierra Foothills. Not sure what your system needs? We'll take a look and give you an honest recommendation.