Fiberglass Pool Basics: Pros, Cons, and How They’re Made
What is a fiberglass pool, in the most basic sense?
Confession: between you and me, I didn’t know the basics of a fiberglass pool until I joined River Pools. I knew what fiberglass was and what a pool was, individually, but I wasn’t sure how fiberglass changed the pool essence and the process. I imagined it as being basically a curvy plastic bowl someone stuck in the ground.
Of course, I’m a pro now, but with vivid memories of how lost I felt at first. So if you’re quietly wondering about the fundamentals of a fiberglass pool, I’m here for you.
We’ll discuss these aspects in layman’s terms:
- Manufacturing process
- Installation process
- Pros and cons
What is a fiberglass pool?
Not a curvy plastic bowl, as it turns out. But I hadn’t been completely off: it’s a one-piece structure made entirely of fiberglass materials.
For comparison, a vinyl liner pool has 1) plastic or metal wall panels and 2) a grout or vermiculite pool bottom with 3) the vinyl liner on top of them.
A concrete pool has 1) a cage of steel bars encased in 2) concrete covered in 3) plaster.
Recommendation: definitely watch our 8-video series on River Pools’ manufacturing process. My coworker Cristian is both funny and informative, and his videos take you into the factory to see the manufacturing process up close.
The fiberglass pool shells manufactured by River Pools consist of six different layers of fiberglass materials, all melded together.
The pool shell typically ends up about ⅜ inches thick. Compare this to a concrete pool, which is 5-6 inches thick including the rebar, and to a vinyl liner pool, for which the wall panels are 4 inches thick (with the liner itself measured in negligible mils).
Fiberglass pools are constructed from a mold in a factory, which is why you have fewer options to customize the size and shape.
At River Pools, our molds are made of fiberglass and reinforced with steel bars. We start with a bright red-orange mold underneath and layer the pool shell on top of it, rather than constructing the shell on the inside of a mold.
What you should ask your manufacturer about your pool mold:
- Is the mold true and level?
- Is the mold reinforced with steel?
- Does the mold have a smooth, maintained finish?
The inside finish is what you see when the pool is in the ground for you to swim in. It’s applied as a gel and then hardens through polymerization (chemical bonding that strengthens it). For obvious reasons, it’s called a gelcoat.
It’s super smooth and durable, and it’s algae-resistant, which is awesome for you in long-term maintenance.
Every time we apply chopped fiberglass, we mix and apply it with either vinyl ester resin or polyester resin. (That’s resin pronounced reh-zin, as opposed to rosin pronounced rah-zin, which you use on a violin bow. Not the same thing. I checked.) The resin works as an adhesive so that the fiberglass sticks to itself and to the surrounding layers of the pool shell.
Analogy time: say I blow up a balloon to papier-mâché it and shred newspaper and mix it with glue before applying it. I could paint the balloon with glue alone, but when it dried and I popped the balloon, the glue wouldn’t keep its shape very well because it wouldn’t have much support. On the other hand, I could stick newspaper alone to the balloon, but it wouldn’t stay there without something holding it to the mold (in this case, the balloon).
The resin is the glue to the fiberglass’s paper. When mixed and applied together, they keep the correct shape with proper support.
Vinyl ester resin is what we use with the first layer of chopped fiberglass because it’s waterproof. It prevents water from passing through the gelcoat into the semipermeable polyester resin, which would make the gelcoat bubble (in osmotic blisters) and separate from the next layer of the pool shell.
Polyester resin is what we use with the other layers of chopped fiberglass. It’s semipermeable, and it mixes with any water that gets into it. With 100% vinyl ester resin as the first layer, no water will pass through to the polyester resin and create bubbles (blisters) in the gel coat. Polyester resin is also less expensive, which benefits your budget.
When interviewing manufacturers, you should ask if the warranty covers the gel coat in case osmotic blisters form.
The two stages of the process
The process for a fiberglass pool involves two separate stages: manufacturing and installation.
Unlike concrete and vinyl liner pools, which are constructed as they are installed, fiberglass pools are actually made in a factory beforehand. The pool shell is then transported to the site and installed there in only a few weeks.
This is why the installation process is so short—most of the work is done before you even see the builders.
The quality check
We look for any cracks or inconsistencies in the fiberglass. While each manufacturer’s process may differ slightly, make sure they quality check the pool shell.
The builder should also weigh the pool shell to make sure it falls within an acceptable range (about 5% of the design specifications). A pool that falls outside that range may have insufficient or faulty material.
You can ask for a dig sheet (the design specs) and compare the weight listed there to the weight logged on the side of your pool.
How are fiberglass pools made?
The short answer: very carefully.
Since the pool is built in the factory, you won’t see this part. Still, you should interview potential manufacturers to be sure they have a solid procedure, experienced builders, and customers you can talk to.
This is the manufacturing process River Pools uses:
- Spray the gelcoat onto the mold.
- Apply chopped fiberglass with vinyl ester resin.
- Apply chopped fiberglass with polyester resin.
- Apply woven roving at stress points for additional strength.
- Apply structural honeycomb materials to support the side walls.
- Apply the final layer of fiberglass with polyester resin.
- Cure in the mold.
- Remove the pool shell from the mold.
- Trim the excess fiberglass.
- Quality check the pool shell.
How are fiberglass pools installed?
Most of the time, pool shell manufacturers work separately from the people who install that pool. In this case, you’ll want to interview the installer in addition to the manufacturer to verify their experience and process and ask for customer references.
River Pools is both a manufacturer and installer, so we’re able to provide a seamless pool project experience.
- Excavate the soil.
- Set and level the pool.
- Install the pool’s plumbing and filter system.
- Backfill the pool shell.
- Install the coping and patio.
- Install the pool fence.
The installation process takes only a few weeks, so you can enjoy your pool all summer long rather than staring sadly at your torn-up yard for months.
What is the average cost?
On average, most fiberglass pool projects cost $45,000–$85,000 in the initial purchase. Extra features and upgrades will increase that price further.
Once the pool is ready for use, you don’t need to purchase many chemicals or run much equipment to kill algae. The continued maintenance and upkeep over the life of the pool will only cost you about $3,750 for every 10-year period. (Compare this to $11,500 for a vinyl liner pool and $27,400 for a concrete pool over the same time frame.)
The low cost and effort for maintenance are a big benefit of this pool type.
What are the pros and cons?
We advocate fiberglass pools because they’re a great long-term fit for many situations, but they do have their downsides. To get a better idea of whether a fiberglass pool is for you, flip through the pros and cons listed here.
Fiberglass Pool Advantages
- Fast installation
- Low maintenance
- Low lifetime cost
- Compatible with salt water systems
The total process to install a typical fiberglass pool usually takes three to six weeks. For comparison, a concrete pool installation can take three to six months.
This speed means less stress in your life. You can enjoy your new pool without worrying about and managing crews in your backyard for months on end.
Fiberglass is strong enough that you don’t have to worry about puncturing the gelcoat or cracking the structure through everyday use. Your dogs can play in the pool with you, no problem.
The inside finish is user-friendly and never needs to be refinished if it’s made correctly.
The gelcoat of a fiberglass pool is smooth and algae-resistant, so you don’t have to brush the surface weekly or use so many chemicals to kill algae (a major downside for concrete pools).
The fiberglass also doesn’t affect the water chemistry, so you don’t have to add in acid to balance the pH.
Low lifetime cost
Fiberglass pools require less electricity and fewer chemicals for maintenance—this not only saves you that time and effort, but it also cuts down your costs.
You don’t have to refinish the fiberglass or replace a liner.
Over a 10-year period, you’d spend less than $4,000 on upkeep, as compared to almost $12,000 for a vinyl liner pool or $28,000 for a concrete pool.
Decades ago, when fiberglass pools first came out, they looked simple and (am I allowed to say this?) kind of ugly. Now, though, you can customize your pool to any aesthetic with colored finishes, spas, ceramic tile, tanning ledges, water features, and awesome lights.
When you install a fence around the pool, you can go as fancy as you want as long as it meets safety regulations.
Compatible with salt water systems
The salt from salt-water chlorinators wears away at concrete and at metal (such as metal wall panels and coping on vinyl liner pools). With fiberglass, you can enjoy high-quality water with low maintenance.
Fiberglass Pool Disadvantages
- Limited options for size and shape
- Initial cost higher than a vinyl liner pool
Fiberglass pools typically run up to 16 feet wide, 40 feet long, and 8.5 feet deep. Because they’re created from pre-designed molds, they have fewer options for shapes and sizes. The manufacturer also has to transport the pool shell to the installation site, so highway restrictions apply.
Despite the limited customization for the basic designs, plenty of features can be added, and most of the time you can find a design you like.
Initial cost higher than a vinyl liner pool
On average, most fiberglass pool projects cost $45,000–$85,000. This includes both manufacturing and installation. Extensive retaining walls, water features, or other special additions add more to that initial price.
However, fiberglass pools have the lowest long-term cost of ownership, compared to concrete or vinyl liner pools. Over 10 years, the maintenance and upkeep would only cost you about $3,750—as opposed to $11,500 (vinyl liner) or $27,400 (concrete).
How do I find a fiberglass pool manufacturer?
We recommend you interview multiple manufacturers so you can compare the methods they use, and contact their customer references.
If you have trouble finding manufacturers in your area, ask a pool builder/installer with fiberglass pool experience what pools he installs and recommends. If possible, ask for (and actually speak with) his customer references to make sure his advice is worth taking.
To be sure you’re getting a great pool shell, look for these solutions as used in our Cross-Lynx Composite Technology:
- Using a level, reinforced, smoothly finished mold
- Allowing the gelcoat to cure in a controlled, ideal environment
- Using 100% vinyl ester resin in the fiberglass layer right underneath the gelcoat
- Reinforcing the stress points with woven roving
- Strengthening the sides of the pool shell with honeycomb materials
How do I find a fiberglass pool installer?
Again, we recommend you interview multiple installers and compare their answers. Speak with their customer references as well.
Ask how they deal with these common problems related to installation:
- Settlement or shifting of the pool shell
- Leaks in plumbing lines and around jets and other pool fittings
- Separation between the pool and patio
- Bulges in the side walls of the pool
To be sure you’re getting a secure installation, look for these solutions as used in our advanced installation methodology:
- Fusing the pool shell and patio together (i.e., with a rod)
- Using plumbing straps to secure the plumbing to the pool shell
- Using all Schedule 40 PVC hard pipe
- Using crushed/chipped stone for the backfill material
- Encasing the plumbing in stone to prevent plumbing settlement
- Having a 12-inch-thick concrete bond beam around the perimeter of the pool
- Monitoring and removing ground water with a sump pipe
What does this mean for me?
Decades ago, there was a stigma that a fiberglass pool looked like a bathtub. However, fiberglass pools have evolved and are now cutting-edge and high-end products installed in homes around the world.
Fun fact: there are fiberglass pools installed in the 1960s that are still in-ground and fully functioning.
The demand for fiberglass pools has doubled over the past decade, whereas vinyl liner and concrete pool demand has diminished or stayed the same. And as far as long-term use, we fully expect fiberglass pools to last for decades. In fact, River Pools provides a lifetime structural warranty for our fiberglass pools.
If you want to look deeper into fiberglass pools as an option for you and your family, you can contact us for a quote and download our ebook.
Editor's note: This blog article was updated on January 2, 2019.