Most pool owners can name their equipment — the pump brand, the filter type, whether they run a saltwater system or a heater. But ask about pipe sizes and most people go quiet. It’s one of those behind-the-scenes details that rarely comes up — until something goes wrong, or until you’re upgrading equipment and realize the pipe underground doesn’t match what you’re trying to connect.
Gunite pool owners especially should understand their pool’s plumbing. Gunite pools are permanent, custom-built structures. The plumbing goes in during construction — encased in concrete and buried underground. You can’t pull it out and start over without a major renovation. Getting it right from the beginning matters enormously. Knowing what’s in the ground helps you make smarter decisions for every upgrade, repair, and renovation ahead.
How Pool Plumbing Works
Your pool’s plumbing system has two sides: the suction side and the return side.
Suction lines carry water away from the pool. They pull from the skimmers at the surface and the main drains at the floor, then deliver it to the pump. The pump draws the water through and pushes it into the filter, heater, salt cell, or any other inline equipment.
Return lines carry that cleaned, treated water back to the pool through the return jets in the walls. Return jets create circulation patterns that prevent dead spots where algae loves to grow.
Everything in the system depends on these two pipe networks being properly sized. Pipe size drives water movement more than pump size does. You can pair a larger pump with larger pipe. You can’t do the same with an undersized pipe.
What Size PVC Pipe Is Used in Gunite Pools?
Inground pools typically use either 1.5″ or 2.0″ PVC pipe — and you’ll often find both sizes in the same system. In a well-built custom gunite pool, each side of the system gets intentional sizing.
Suction lines (skimmers and main drains): 2″ PVC
Suction lines carry the heaviest water volume and put the most demand on the system. Running 2″ on suction lines lets the pump pull water without cavitation. Cavitation happens when an undersized pipe starves the pump of water. It strains the pump, cuts efficiency, and shortens equipment life.
Return lines: 1.5″ PVC
Return lines run 1.5″ PVC to maintain proper water pressure back to the pool. The slightly smaller diameter on the return side actually helps sustain the pressure needed to push water through the jets effectively.
Equipment pad plumbing: 2″ PVC
Filter systems use 2″ PVC to increase flow rate and deliver maximum pressure. The larger diameter eliminates back pressure that can cause pump and filter problems.
For larger or more complex custom gunite pools — those with spas, water features, tanning ledges, deck jets, or in-floor cleaning systems — smaller dedicated lines (¾” or 1″) handle those additional runs.
Why Pipe Size Matters More Than Most People Think
This is where a lot of pools — even expensive ones — quietly get shortchanged. An undersized plumbing system can’t be fixed by upgrading the pump. In fact, putting a more powerful pump on undersized pipe makes things worse.
Above approximately six feet per second, water velocity creates a sharp drop in system efficiency. The water begins to swirl, forming vortices and turbulence that fight against smooth flow. Friction losses increase rapidly as velocity climbs.
Here’s how maximum flow efficiency at 6 fps breaks down by pipe size: 1.5″ handles up to 38 GPM, 2″ handles up to 63 GPM, and 2.5″ handles up to 90 GPM. A pool with undersized pipe simply can’t move water efficiently — no matter how much horsepower sits behind it.
Consider this: a pool with 2.5″ plumbing and a ¾ HP pump will outperform one with 1.5″ pipe and a 1.5 HP pump. That’s how much pipe size matters relative to pump size.
What Type of PVC Is Used?
Most inground pools use white Schedule 40 PVC pipe, Type 1, Grade 1. Schedule 40 is the standard for pool plumbing and suits nearly all residential applications.
Properly installed, rigid Schedule 40 PVC pipe can last over 75 years. That longevity matters in a gunite pool, where the pipes sit encased in concrete and you can’t access them without major work.
One important note for pools with heaters: standard Schedule 40 PVC can’t handle high water temperatures. Many pool plumbers use CPVC pipe for heater and pump connections instead. CPVC withstands temperatures up to 200°F and holds up when heaters shut down before completing a proper cool-down cycle.
How Plumbing Is Installed in a Gunite Pool
In a gunite pool, plumbing goes in before the shell. The pipe layout takes shape during the steel phase, before any concrete goes down. Crews run all suction and return lines from the pool structure out to the equipment pad, pressure-test them, and then lock everything in place when the gunite applies.
This is exactly why your pool builder’s plumbing plan matters so much. Running plumbing lines directly through the gunite shell protects them, reduces the chance of damage, and increases flow rate by keeping a direct route from pool to filter. Every additional fitting — every elbow, tee, and valve — adds friction and reduces flow. A smart plumbing layout minimizes those losses from day one.
What to Know When Upgrading Equipment
If you’re replacing a pump, adding a heater, or installing a salt chlorine generator on an existing gunite pool, know your pipe size before you buy anything.
Your pump and filter unions must match the connecting pool pipe size for proper water circulation. Mismatched connections create leaks, reduce efficiency, and can damage new equipment.
If you don’t know what size pipe your pool has, a pool professional can assess your equipment pad connections and identify the pipe size — usually without any excavation. It’s a quick diagnostic step that can save you from buying equipment that won’t work with your existing system.
PEC Builds Gunite Pools With Properly Sized Plumbing From the Start
At Pinnacle Exterior Construction, we design and build custom gunite pools throughout Baton Rouge and the surrounding area — and the plumbing plan is one of the first things we get right. Every pool we build gets sizing specific to its volume, features, and equipment, so you’re not inheriting an undersized system or a layout that limits what you can add later.
If you’re planning a new pool or working through a plumbing issue on an existing one, our team is happy to walk you through it.
Contact PEC today or explore our pool construction process to see how we build.