Yes, in almost every case. An in-ground pool, a permanent above-ground pool, and most of the big seasonal pools sold at warehouse clubs and big box stores all need a building permit, and usually a zoning permit and an electrical permit on top of it. The only pools that skip the building permit are the small, shallow ones, and the line is lower than most people expect.
The 24-inch rule
Pennsylvania's Uniform Construction Code exempts prefabricated swimming pools that are less than 24 inches deep. That's the kiddie pool, the splash pad, the inflatable ring pool for the toddlers. Anything that can hold 24 inches of water or more is a swimming pool in the eyes of the code, whether it's concrete, vinyl-lined steel, or an inflatable you bought on sale in May.
The test is how deep the pool can be filled, not how deep you plan to fill it. A 48-inch pool you keep half full is still a 48-inch pool. The state exemption also only holds if the pool doesn't violate a local ordinance, so a municipality can still regulate smaller pools through zoning, and some do.
Seasonal pools count too
This is the one that catches people. A 15-foot inflatable or soft-sided pool that goes up in June and comes down in September is not exempt just because it's temporary. If it's 24 inches deep or more, it needs a permit and it needs a barrier. Some municipalities issue a simpler seasonal permit for these, and some want a new one every year. Ask before you buy, because the answer can change which pool you buy.
The barrier is the main event
Most of what the building department cares about with a residential pool is keeping small children out of it when nobody is watching. Pennsylvania's code uses the International Swimming Pool and Spa Code for this, and the barrier rules are specific:
The barrier has to be at least 48 inches high, measured on the outside, away from the pool. The gap at the bottom can't be more than 2 inches. No opening anywhere in it can let a 4-inch ball pass through, and chain link and lattice need even tighter openings unless they're slatted. Horizontal rails closer together than 45 inches have to be on the pool side, so they don't work as a ladder.
Gates are where a lot of inspections fail. A pedestrian gate has to open outward, away from the pool, and be self-closing and self-latching. The latch release has to sit at least 54 inches above the ground, or if it's lower, on the pool side of the gate where a child reaching over or through can't get to it. Gates also need to be able to take a lock.
If the back wall of your house is part of the barrier, any door that opens onto the pool area needs an alarm, or another approved safeguard like a power safety cover. That surprises a lot of people who assumed the house was the easy side of the enclosure.
Our fence permit guide covers the zoning side of fences in general. A fence that doubles as a pool barrier has to meet both sets of rules, so settle the pool plan first and build the fence to match it, not the other way around.
Above-ground pools and the ladder
For an above-ground pool, the pool wall itself can serve as the barrier if it's at least 48 inches high. The weak spot is the ladder. It has to be removable, lockable, or surrounded by its own compliant barrier, so the pool isn't one easy climb away from a curious five year old. Lean-to steps left in place overnight are exactly the thing the inspector is looking for.
Watch what sits next to the pool, too. A deck, a filter, a stack of patio chairs, or a planter right up against the wall can turn a compliant barrier into a step stool.
Hot tubs
Hot tubs and spas are covered by the same code, but there's a useful exception. A spa with a lockable safety cover that meets the ASTM F1346 standard doesn't need a separate barrier. Many locking hot tub covers are sold as meeting it, so check the label or the paperwork. The electrical side still needs a permit, and a hot tub on a deck raises the question of whether the deck can carry the weight of a few thousand pounds of water and people.
Electrical is its own permit
Pumps, filters, heaters, lights, and the outlets near the pool all need an electrical permit and inspection, separate from the pool permit. Pool wiring rules are some of the strictest in the electrical code. Expect requirements for ground-fault protection, bonding of the pool structure and equipment, limits on how close outlets and switches can be to the water, and no overhead power lines over or near the pool. The inspector will want to see the underground wiring and bonding before it's buried, so schedule that inspection before you backfill.
Plugging the pump into the nearest outdoor outlet with an extension cord is not a wiring plan. It's also one of the most common ways people get hurt around backyard pools.
Zoning: where the pool can go
Zoning decides where on your lot a pool can sit. Typical rules keep pools out of the front yard and set minimum distances from side and rear property lines, sometimes with separate setbacks for the pump and filter so the neighbors aren't listening to it all night. An in-ground pool and the patio around it also count against your lot's impervious coverage limit, which matters on the smaller lots in a lot of Delaware County boroughs. Go over that limit and you may need stormwater controls or a variance from the zoning hearing board.
Your zoning officer can tell you the setbacks and coverage limit for your property. Get them before you pick a pool size, not after.
In-ground pools: digging and water
An in-ground pool means excavation, so PA One Call (dial 811) is required at least three business days before digging. Some municipalities also want a grading or stormwater review for the excavation and the new hardscape, especially on sloped lots or where the backyard already holds water after a storm.
Ask about draining, too. Plenty of towns have rules about where pool water can go, and pumping a full pool of chlorinated water into the street or onto the neighbor's yard is a good way to meet your code enforcement officer.
What happens when you sell
A pool that was installed without permits tends to come up when the house sells. Many Delaware County towns require a resale U&O inspection, and pool barriers and gate latches are on a lot of those checklists. A buyer's home inspector will flag a missing permit or a non-compliant barrier too. If you have an existing pool with no permit history, our guide to selling a house with unpermitted work walks through how to legalize it.
The practical path
Call your municipality before you buy or sign anything, and ask three questions: does this pool need a building permit, what do zoning setbacks and coverage allow on my lot, and do they issue seasonal permits for temporary pools. If a pool company is doing the install, ask who is pulling the building and electrical permits and make sure the contract says so. Then plan the barrier and gate along with the pool, schedule the electrical inspection before anything gets buried, and don't fill it until the final inspection passes.
More
Find your municipality's permit and zoning contacts. See also the permit FAQ, the glossary, Do You Need a Permit for a Fence in Delaware County, PA?, and Do You Need a Permit to Build a Deck in Delaware County, PA?.