Why Does My Fibreglass Pool Have Bubbles or Blisters?

‍

If you’ve noticed strange little bumps or bubbles forming on the surface of your fibreglass pool, you’re not alone — and no, you’re not going crazy. These bubbles are real, and they’re a red flag for a hidden issue that can quietly destroy your pool from the inside out.

Osmosis. And once it starts, it doesn’t stop.

‍

So, What Is Osmosis in a Fibreglass Pool?

‍

Osmosis is a chemical reaction that happens when water penetrates the surface of your pool shell, passes into the fibreglass layers, and gets trapped.

‍

Inside the fibreglass structure, this moisture mixes with leftover chemicals and uncured resin from when the pool was first built or resurfaced. Over time, this creates acidic fluids and gases, which get trapped under the surface. As pressure builds, the fibreglass begins to blister — forming soft, raised bubbles that can look and feel pretty nasty.

‍

What Causes It?

There are a few common reasons this happens:
• It could have started in the plant when manufactured - cheap or inferior resins used during manufacturing or past repairs
• Poor surface preparation before resurfacing
• High heat and chemical load over time (especially in older pools)
• Microscopic breaches in the gelcoat layer allowing water to get in

‍

It’s more common than most people realise — but the longer you ignore it, the worse (and more expensive) it gets.

‍

Warning Signs You Might Be Dealing With Osmosis

‍

You might have osmosis if you’re seeing:

‍
• Blisters, bubbles, or soft lumps under the surface
• Discolouration or staining around the blisters
• A rough texture in spots that used to be smooth
• Sharp areas or cracking as the blisters break down

‍

If your pool is more than 10 years old, or if it’s been resurfaced before, you should definitely keep an eye out.

‍

‍

How Duraglaze Fixes Osmosis — Properly

‍

At Duraglaze, we don’t patch over osmosis — we rebuild the surface the right way. We’ve spent decades working on fibreglass pools across Sydney, and we’ve seen first-hand what shortcuts look like. That’s why our process is detailed, tested, and built to last.

‍

Here’s how we fix it:

‍

1. We grind back all the affected areas. We go right down to solid laminate, removing every blister and soft spot. If you don’t do this, the problem just comes back worse.

‍

2. We prime and seal the surface where bubbles were removed, increasing the waterproof nature of the produce and forming the first layer of a chemical bond in the rebuild of the pool surface. Most importantly - don't cheap out on the product. Only use high-performance resins. No budget mixes here. We use the best resins available on the Australian market, designed to resist water penetration and chemical breakdown long-term.

‍

3. Once we’ve removed all the damage, we rebuild the pool shell using multiple layers of fibreglass matting — but here’s the critical part:

‍

Those layers are applied within hours of each other, not days or weeks apart like some operators do.

‍

If the weather delays us, we don’t just keep going — we stop, prep again properly, and chemically reactivate the resin surface before applying the next coat. That’s the difference experience makes.
‍

We’ve developed and tested this process over decades. It ensures every layer bonds correctly and cures with full structural integrity. The result? A tough, watertight pool shell that lasts.

‍

4. We finish with a bulk filler followed by a protective topcoat. That means a smooth, strong, chemically-resistant surface that looks incredible and lasts for years.

‍

We have completed hundreds of Osmosis Repair and Fibreglass Pool Resurfacing Projects. However, a recent resurfacing project on the Northern Beaches in Sydney took the cake. With some of the worst osmosis we have ever seen, we removed every bubble, rebuilt the surface, and gave the client a like new finish. Completed the deal with a new paving and coping, and added a mosaic tile to the waterline with epoxy glue and grout.

‍

‍

‍

‍

‍

Osmosis is like cancer for fibreglass pools — silent, ugly, and destructive if ignored. But it’s fixable. And with the right system, process, and attention to quality details you give your pool its best chance at a new lease on life for many years ahead.

‍

If you’re seeing blisters, don’t just ignore them or cover them up. We are happy to come and have a look, give you the right advice, and restore your pool properly. But if you are considering taking a short cut, or using a lower quality process you may be best to do nothing at all.

‍

‍

So you have osmosis - now you have to avoid the most common pool resurfacing mistakes!

When it comes to resurfacing a fibreglass pool, cutting corners doesn’t just waste money — it can leave your pool in worse shape than before. Here are the most common mistakes we see from rushed jobs, cheap quotes, and DIY attempts:

‍

❌ 1. Using Cheap or Low-Quality Resins

This is the big one. If the resin can’t handle constant water and chemical exposure, blisters and delamination are only a matter of time. Some contractors use budget materials to win the job — but you’ll pay the price later.

✅ At Duraglaze, we use only the highest-grade resins available in the Australian market.

‍

‍

❌ 2. Skipping Proper Surface Prep

Blisters don’t just sit on the surface — they form inside the fibreglass. If you don’t grind out every damaged area and prep the substrate properly, the problem will return, fast.

✅ We remove every blister and rebuild from solid laminate — no shortcuts.

‍

❌ 3. Applying Layers Days (or Weeks) Apart

Fibreglass layers need to bond chemically to create a strong shell. Waiting too long between coats means poor adhesion and future failure. Weather is out of your control, but project management is not.

✅ We apply layers within hours, not days. If weather delays us, we properly prep and reactivate the surface before continuing. We also dedicate a team to each job, and stay with it until the end. Contractors who charge less, need to run several jobs to keep things boyant. This leads to mistakes, misteps, and mechanical bonds between layers. Our clients value dedicated service and we enjoy providing it.

❌ 4. Painting Over the Problem

Painting over osmosis or chalky gelcoat is like putting a band-aid on a leak. It might look okay for a while — but it’s not a solution.

✅ We rebuild, not disguise. A proper resurface isn’t paint — it’s a structural repair.

❌ 5. Trusting the Wrong Contractor

If they can’t explain their process or quote you properly, chances are they’re not doing it right. Look for a contractor who understands why each step matters — not just what it costs.

✅ We’ve been resurfacing pools for decades. We’ll explain what’s happening, why it matters, and what your options are.

💡 Sometimes doing nothing is better than doing it badly.

If you’re considering a quick fix or a cheap job, let us give you an honest opinion first. We care about your pool — and your long-term outcome.

‍

👋 Ready to Talk?

Reach out for a quote or inspection. We’ll show you what’s going on, what it’ll take to fix it, and how to protect your investment for the long run.

‍

This artical is presented by the team at Duraglaze Pool Resurfacing and Pool Renvations, Servicing Sydney’s North Shore, Northern Beaches, Eastern Suburbs & beyond

‍

‍

‍