Tennis balls lose pressure - here's why and what you can do about it

You open a new can of tennis balls. You hear a small hiss. From that second, air slowly begins to seep out - and it doesn't stop.

It's nothing you're doing wrong. It's simply the nature of rubber. And it costs you more than you might realize.

What happens to a tennis ball over time?

A factory-new ball is pressurized to approx. 14 PSI internally. This pressure gives you the precise bounce, rebound from the strings, and the control you know from new balls.

From the moment the can is opened, the pressure drops. Not only because you play with the balls - but also simply because they are exposed. Rubber is porous. Air seeps through and is drawn towards the lower pressure outside.

A pressure drop of 2-4 PSI after 1-2 weeks of use doesn't sound like much. But you'll notice it clearly:

• The ball bounces lower and more erratically
• The rebound from the strings feels softer
• It's harder to generate spin and control
• Topspin and slice react differently than you expect

Many players gradually adapt. They think the balls are just "like that." They're not. They've lost pressure.

Three factors that determine how quickly balls go flat

Temperature - the most important factor
Heat makes rubber more permeable. Air seeps out faster in warm environments. Balls stored in a warm car trunk in the summer can lose pressure twice as fast as balls stored cool indoors.

Conversely: cold compresses the gas inside and the balls feel flat and hard. This is not permanent damage - it's physics. Warm them up before playing and they'll play like new again.

Humidity
Moisture penetrates the rubber and affects elasticity. Balls stored in damp changing rooms or basements lose playing characteristics faster. Always store balls dry and at room temperature.

Altitude
If you play at higher altitudes - e.g., mountain regions - the balls behave differently because the pressure difference between inside and outside changes. The ITF approves special "high altitude" balls for play above 1,200 meters for precisely this reason.

When is a ball actually worn out?

There's a difference between a ball that has lost pressure and a ball that is worn out.

A pressure drop can be corrected. Felt wear cannot.

The felt layer wears down with each hit. The rubber core can crack with intensive use. When the felt layer is noticeably thin and the ball feels slick, pressure restoration won't help. It's worn out.

But most balls are discarded long before that point. They are discarded because the pressure has dropped - not because the felt is worn. This is a waste of money and resources.

How to test if your balls still have enough pressure

The simplest test: drop the ball from shoulder height onto a hard floor. A ball with good pressure bounces up to approximately hip height. A ball with low pressure bounces significantly lower and seems "dead."

Another indicator is your arm. Does it require more force to play with the balls than usual? That's a sign that the pressure has dropped.

You gradually get used to the pressure loss and barely notice it. Compare it with a new ball from an unopened can - the difference is clear.

What you can do about pressure loss

The easiest solution is to store the balls under pressure. When the pressure outside the ball is higher than inside, air seeps into the rubber instead of out. The ball regains its bounce.

This is exactly what Pressurebox does. You place the balls in the container after playing. Pressurebox Pro automatically raises the pressure and maintains it overnight. The next time you open it, the balls play like new.

Tests show that balls can be repressurized 4-5 times with bounce close to new levels. The active player thus uses significantly fewer cans per year.

What does it really cost to play tennis?

A can of 3 balls costs 50-80 DKK. Here's what that adds up to:

• Recreational player (2x/week, changes monthly): 600-960 DKK/year on balls
• Active player (4x/week, changes every 2 weeks): 1,400-2,200 DKK/year on balls
• Club player with training (daily): 3,000-4,000 DKK/year on balls

Pressurebox Pro costs 999 DKK and pays for itself in 1-2 months for the active player. The savings are up to 80% of the annual ball budget.

Padel and tennis - same principle, different pressure

Tennis balls and padel balls work on the same principle but are built for different pressures. A padel ball is pressurized to approx. 11 PSI, a tennis ball to approx. 14 PSI.

Both types lose pressure for the same reasons. And both types can be refreshed with Pressurebox.

Read about why padel balls lose pressure - and what you can do about it.

Frequently asked questions about tennis balls and pressure

How many times can I refresh a ball?
Most balls can be repressurized 4-5 times and still have good bounce. After that, felt wear begins to take over as the limiting factor.

Should I start using a pressure container from the first time I open a can?
Yes. Balls with full pressure are refreshed faster and easier than balls that are already flat. Start from day one to maximize the balls' lifespan.

Can I use the same Pressurebox for padel and tennis balls?
Yes. Both Pressurebox models work for both ball types.

Are pressureless balls a better choice?
Pressureless balls don't lose pressure, but they are harder and require more arm strength. Most players prefer pressurized balls and use Pressurebox to keep them fresh.

What about balls that have been lying around for six months?
Balls that have been unopened in a sealed can retain pressure for a long time. Opened balls that have been lying around for 6 months are likely almost flat - but can often be repressurized with Pressurebox, it just takes a little longer.