Many assume a hot tub functions like a small pool: fill it, add chemicals, cover it, and use it for weeks. In reality, a fiberglass hot tub is quite different. Treating it like a pool can cause damage, increase maintenance costs, and reduce its lifespan. Before leaving water in your tub for extended periods, consider the following: what is the difference between a fiberglass hot tub and a pool, and why does it matter?
Why a fiberglass hot tub is not the same as a pool?
At first, a hot tub might look like a small pool – both have water and warmth, and both offer a place to relax. But the way they’re built, their purpose, and how you care for them are actually very different. Knowing this difference helps you take better care of your hot tub.
Pools are built to hold water year-round and keep it clean through constant filtration. Fiberglass (or fiberglass with 3D Granite effect) hot tubs, especially those made from classic polyester, are meant for short sessions and easy draining. They’re made for a simple reason: to give you a focused, relaxing soak, not to act as a small pool. And that’s exactly how they should be used.
If you leave a traditional hot tub full of water for days, the water can slowly seep into the shell. This is called osmosis, and it can lead to hidden damage such as blistering, layers separating, and tiny cracks. You might not notice these problems right away, but they build up over time and can weaken your hot tub.
To use your classic hot tub correctly and keep it in top condition:
- fill the clean tub for each use
- enjoy your soak
- drain the water afterwards.
Want to keep water in your hot tub longer? OsmoGuard™ makes it possible.
Today’s lifestyle asks for more flexibility. Many people want to enjoy their hot tub for several days in a row, keep the water warm between sessions, and use gentle water treatments – like chlorine or active oxygen – to maintain freshness. It’s a natural wish: to have a hot tub that’s always ready, without the routine of draining and refilling after each use. However, classic fiberglass hot tubs are not designed for this use. Leaving water in the tub for extended periods, especially when chemicals are present, increases the risk of osmosis and related damage. So, what’s the solution?
OsmoGuard™ hot tub shells feature an enhanced structure with a vinyl ester fiberglass layer replacing the standard polyester. This ensures superior resistance to osmosis, including blistering, delamination, and long-term water damage.
That’s where OsmoGuard™ comes in – an innovation designed specifically for those who want the ease of water retention without compromising the tub’s health or lifespan. .OsmoGuard™ isn’t a separate product. It’s the name Maudis gives to a specific shell configuration – one that features a vinyl ester fiberglass layer seamlessly integrated between the outer gelcoat and the structural laminate This invisible upgrade quietly transforms how your hot tub performs over time.
How long can you store water in an OsmoGuard™ hot tub?
While classic fiberglass hot tubs require draining after every use, OsmoGuard™ shells are designed to hold water for 2 to 4 weeks, depending on how often you use the tub and how well the water is maintained. This is a game-changer for anyone who wants their tub to be ready more often and with less effort. This makes OsmoGuard™ the ideal choice for outdoor spa setups, where convenience and comfort go hand in hand. Whether your tub is placed in a private backyard, a guesthouse terrace, or a countryside retreat, the ability to keep water fresh longer means fewer interruptions and more time soaking under the sky.
And you’re not limited by design. At Maudis, OsmoGuard™ shell is available across Maudis’ core collection, including classic round models, Ofuro tubs, and our modern, square hot tub designs. Whichever form fits your setting, you can now enjoy longer-lasting use without compromising structural integrity.
OsmoGuard™ is strong, but not indestructible
While its enhanced structure provides strong resistance to water and chemicals, proper care is still required to maintain optimal performance. One of the most important rules is to never leave water in your hot tub during freezing weather unless it is heated. OsmoGuard™ does not protect against ice expansion. If water freezes inside the shell, it can crack internal layers and cause irreversible damage, even with a reinforced structure. Therefore, draining your tub in sub-zero temperatures is essential, especially for outdoor spas exposed to harsh winters.
While OsmoGuard™ is compatible with standard disinfectants, it is not designed for aggressive chemical cleaners, abrasive tools, or solvents such as alcohol, acetone, or strong acids and alkalis (pH above 8.0). These substances can damage the gelcoat or decorative surface. Never place undissolved chlorine tablets or granules directly on the surface. Always use a floating dispenser or pre-dissolve them before adding.
These care guidelines apply to all shapes and finishes, including square hot tubs, traditional round designs, and deep Ofuro models. OsmoGuard™ provides reliable protection, but it is most effective when combined with proper maintenance.
Using your OsmoGuard™ hot tub the right way
Enjoy more freedom with just a few simple rules. OsmoGuard™ gives your fibreglass hot tub the durability it needs for longer use, but smart use is key to keeping it performing at its best. Here’s how to care for your tub so you can enjoy its benefits for years to come.
By following basic maintenance, you can safely store water in your OsmoGuard™ shell for 2 to 4 weeks. Using automatic disinfection systems, such as ozone or UV, extends the freshness of the stored water. This is particularly beneficial for outdoor spas where you want the tub ready for use without daily draining.
Engineered for durability, OsmoGuard™ tolerates manufacturer-recommended levels of key spa chemicals like::
- Free chlorine: 1.0–3.0 mg/l (temporary rise to 5.0 mg/l is acceptable)
- Active oxygen (MPS): up to 10 mg/l
- pH range: 7.0–7.6
- Ozone and UV: fully compatibl
With proper maintenance, an OsmoGuard™ shell offers lasting resistance to water osmosis, ensuring peace of mind for any tub model in your spa area.
Is OsmoGuard™ right for you?
If you want your fiberglass hot tub to fit your lifestyle, OsmoGuard™ is the upgrade you need. This shell configuration is ideal if you: have an electric or wood-fired hot tub, prefer to use your tub for several days without frequent draining, want to maintain water hygiene with minimal effort, have an outdoor spa near your home, sauna, or countryside retreat where convenience is important.
With OsmoGuard™, your hot tub becomes part of your weekly routine, ready whenever you are. Maudis offers OsmoGuard™ technology across all key models, including round tubs, Japanese-inspired Ofuro designs, and spa-inspired square hot tubs. Whether your spa area is traditional, modern, minimalist, or textured, there is an OsmoGuard™ solution to fit your lifestyle.
Are you ready for a hot tub that fits your schedule? Explore our OsmoGuard™ collection and choose a durable tub designed for your needs.
