Solar Pool Cover Bubbles: Face Up or Down?

You may have heard that a solar cover can help keep your pool warm without relying on a state-of-the-art pool heater. Sounds good, but now that you have a solar cover in your hands, you’re unsure of which side goes where. One side should be smooth and the other side covered in bubbles. Do the bubbles face up or down?

The bubbles on your solar pool cover should face down. In other words, the bubbles should be touching your water. The air bubbles trap heat and transfer it to the water, warming your pool. If you place the smooth side facing down, it can decrease its lifespan and your pool will not be any warmer in the meantime.

In this article, I will go over how to correctly place your solar cover over your pool – the right way, the wrong way, and why it makes such a big difference. Let’s begin.

Why use a solar pool cover?

A solar pool cover can do everything a regular pool cover does and more. For instance, in addition to preventing debris and evaporation, solar covers can also insulate heat and even transfer it to the water to heat it up.

To be clear, solar pool covers are not as effective as a gas or electric pool heater since solar covers do not generate heat on their own. They rely on an external source of heat such as the sun or a pool heater to really work its magic.

However, for pool owners living in a sunny area, solar pool covers can save them a lot of money as they can just rely on the sun’s UV rays to heat their pool. Solar pool covers can extend your swimming season by keeping your water warm throughout the days and nights even as the temperatures drop.

Conversely, if there is not enough sunlight where you live, a solar pool cover will not be able to heat your pool unless you also have a pool heater.

If you have a rectangular pool, solar covers are easy to put on. The issue is when your pool has an irregular shape. In that case, you can trim your solar cover into the exact shape of your pool. That said, you don’t want to mistake trimming the pool cover with the bubbles facing the wrong way.

Should the solar pool cover bubbles go up or down?

Is there a difference between whether the bubbles on a solar pool cover face up or down? How about for different pool types such as in-ground or above-ground pools?

The answer is that the bubbles should always be facing downwards towards the water no matter what the pool type.

These bubbles, which look like bubble wrap that you might find in packaging, trap heat and are a major part of why solar covers provide so much insulation for your pool.

When facing downwards, the bubbles can be submerged in the pool water and transfer heat from within to your pool.

On a hot, sunny day this allows your solar cover to heat up your pool water. On chillier days, the air bubbles will prevent heat from escaping and keep your water temperature nice and cozy.

So if your pool is an irregular shape and you need to cut a sheet of solar pool cover down to size, make sure you’re doing so with the bubbles facing downwards.

What if the bubbles are facing up?

Some pool owners mistakenly place the solar cover on such that the bubbles are facing up, but all they are doing is rendering the pool cover ineffective.

Since the bubbles that trap heat aren’t facing the water, heat is not being transferred to the water to warm it up. Furthermore, the bubbles can potentially overheat when left in direct sunlight.

Even when a solar cover is taken off, it should be stored in an area out of direct sunlight or have a reflector wrapped around it.

This is because if the bubbles aren’t touching water and transferring heat, they can get damaged by the excess heat they are storing.

The next time you use the solar cover and you do finally place the bubble side down, it may already be damaged beyond repair to be effective.

What else you should know about your solar cover

It may cause algae growth

Some pool owners had the shock of their life when they took off their solar cover only to find the surface of their pool covered in green.

Unfortunately, a side effect of warming up your pool is that it puts it in the optimal temperature range for algae to grow.

If your pool pump is not running, the water will not only be stagnant, but the heat will not be distributed evenly. The water will be much warmer at the surface where the bubbles are touching, and much colder on the bottom.

Not only is this an unpleasant sensation for when you swim, but the warm surface layer is ripe for algae to grow.

To prevent this, you should run your pool pump while the solar cover is on to ensure the warm water is circulating evenly.

You should also be testing your water to ensure the chemicals are balanced and that there is ample chlorine in the pool.

If you still notice the water turning green, then you may need to use an algaecide to eliminate the algae in the pool.

It should be rinsed at least once a week

So much emphasis is placed on cleaning and caring for the pool that sometimes the other pool equipment gets neglected.

In the solar cover’s case, not much maintenance needs to be done. Every week or two, you should give your solar cover a thorough rinse. You don’t even need to use soap or anything fancy, but make sure you’re rinsing every square inch of it.

That way, you can prevent algae from growing on the solar cover itself and ensure that it won’t transfer anything funky to your water.

It won’t work miracles

Even with the bubbles facing down and transferring heat to your water, some people have the wrong expectations for what a solar cover can or can’t do.

While it can potentially help you start pool season just a bit earlier and extend it a bit longer into autumn, it won’t work miracles.

Once winter approaches, the effectiveness of a solar cover alone starts to diminish significantly. With how cold the outside temperature is, coupled with the fact that there will be less sunlight in the day, the solar cover will not be able to keep your pool warm in the winter alone.

That said, solar covers can be used in tandem with pool heaters. In fact, it is recommended. The solar cover will ensure that the heat generated by the heater will not so easily escape, and so you won’t need to run the heater for as long before it can completely warm your pool.

A solar cover alone is useful in the summer, but once the weather starts getting colder, it needs some help to warm your pool. And if your bubbles are facing the wrong way, it won’t be able to help you at all even during the proper season.