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How to Clean a Green Pool

There’s nothing worse than heading out to the pool for a refreshing dip and finding a green lagoon. A green pool can feel like a disaster, and it can happen quickly, almost overnight. But if your pool has turned green, all hope is not lost. You can usually get your pool back to crystal clear in just a few days. It will take a time commitment and some manual labor, but going from green to clean is really not so bad. All you need to know is how to clean a green pool. Of course, if you’re feeling overwhelmed or just don’t have the time to restore your pool, The Pool Butler is happy to help. Our experts have rescued plenty of green pools and know how to do it in record time.

Why is My Pool Green?

A green pool almost always means that your pool has been overtaken by algae. Algae can refer to a broad variety of aquatic plants. It is not a technical term, so there is no specific definition of what is and isn’t algae. However, one defining characteristic of algae is that they use chlorophyll as their primary photosynthetic pigment. The presence of lots of chlorophyll is what turns your pool green.

Typically, a pool is kept algae free by its water chemistry and the power of the pool filter. Chlorine, a vital ingredient is almost all swimming pools, kills algae and prevents them from growing in the first place. The filter can collect any particulate, including algae and their food, and remove them from the pool water. When the levels of free chlorine in the water drop too low, there isn’t enough chlorine to kill algae. So algae begin to grow and can bloom into a huge mess very quickly.

In some cases, pool water can be green, but without any signs of algae. The typical appearance is green-tinted water that is nevertheless clear of particulate debris. Clear green water can be caused by metals dissolved in the water. If that’s the case, check your pool pH to make sure you are not corroding the metal components of the pool, such as railings and ladders. There are some chemicals made to remove dissolved metals from water. Just ask about it at your local pool store. You can also use sequestering agents to prevent metal staining in the future.

We’ll deal with algae here since they are by far the more common cause of green pools.

How to Clean a Green Pool [infographic]

Preparing to Treat the Pool

Before you start to clean a green pool, it’s essential to find out the chemical situation of your pool and deal with that before moving forward. The most important numbers to know are your free chlorine and pH. Chances are good that if you have algae, you have very, very little free chlorine. It is best to maintain 1.0 – 3.0 ppm of free chlorine. For reference, that’s less chlorine that in typical drinking water. So if your free chlorine drops below 1.0 ppm, there is almost nothing standing in the way of a giant algae bloom.

In addition to determining your free chlorine level, you need to know your pH level. A high pH makes chlorine less effective. Also, if it is too low, you will need to raise the pH. Use pH increaser of pH decreaser to bring the pH to about 7.8. That’s a bit high for swimming but perfect for killing algae. Make sure to run the pump to spread the pH increaser or decreaser throughout the pool.

Once the pH is stable, make sure your filter is at its best. You’ll need to run the filter for 24 hours a day to clear out the algae, so it should start out as clean as possible. Clear out any large debris, like leaves and twigs, from the skimmer basket. Then, either backwash your filter or rinse the cartridge on a cartridge filter.

Finally, you are ready to get to the algae. Use a pool brush to scrub the sides and bottom of the pool. This will loosen as much algae as possible and release them into the water. That way, the chemicals you are about to add will have the best chance at killing the floating algae.

Shocking the Pool

Here’s where you bring in the big guns, so to speak. If low chlorine levels are an invitation for algae to flourish, shock is the opposite. Shocking your pool really just means adding lots of chlorine all at once. You should use pool shock, which is concentrated chlorine. You can get it at any pool store. Follow the directions on the package to determine how much shock is needed for your pool size.

Typically, shock comes as either a powder or a liquid. Turn on your pool pump to get the water circulating, then broadcast your shock throughout the pool. In other words, don’t dump the shock all in one spot. Walk around the pool and try to spread it out as much as possible. With the help of the pump, you want the shock to disperse evenly throughout the whole pool. This should kill the algae. If you have a really intense algae bloom, you may need to apply pool shock more than once.

Once the algae are dead, your pool will look cloudy. Don’t worry. Just keep the filter running 24 hours for a few days to clean out all the dead algae. Your water should get clearer as the filter does its work. Your filter is working hard, so make sure to turn it off for a few minutes each day and clean it out. This will keep it from getting clogged and make it more efficient at cleaning your pool water.

Keep testing the pool water. When the free chlorine drops to 5.0 ppm, you can add some algaecide to help along the process of killing off algae. You may also need to add some flocculant, which helps the dead algae clump together and makesthem easier for the filter to catch.

Cleaning Up the Pool

To get the pool all the way clean, you will have to get all the dead algae out of the water. When the algae die, they lose their green color and will just make your pool look cloudy. Some of it will be suspended in the water, which causes the cloudiness, and some will fall to the bottom of the pool. Keep running the filter non-stop to clear out the floating algae. At the same time, brush the sides and bottom of your pool to loosen any algae that are still sticking to them. Finally, make sure to vacuum the bottom of the pool to get rid of dead algae that sink to the bottom.

Depending on how bad the algae bloom was, it may take a few days to get the pool back to normal. However, with regular brushing and vacuuming and with the filter running 24 hours a day, you should have clear water again in no more than 5 days.

Prevent Another Green Pool

After dealing with a green pool, you probably want to make sure it doesn’t happen again. Cleaning it is a laborious process, and both the chemicals and running your filter 24 hours a day cost money. Plus, the whole process can put your pool out of commission for a week.

To avoid another algae invasion, make sure that you keep at least 1.0 ppm of free chlorine in the water at all times. That means testing and adjusting the water chemistry regularly, at least 2-3 times a week. If you’re going to be out of town and away from your pool for a more than a few days, make sure that you have a way of keeping the pool chlorinated. Some pools have a chlorinator built into your pool’s plumbing system. Just make sure it has enough chlorine before you leave. If you don’t have a chlorinator, you can get a relatively inexpensive floating chlorinator that holds slow-release chlorine tablets to maintain a sufficient level of free chlorine in the water.

Of course, if you want to make sure that your pool is always well cared for and crystal clean, nothing beats regular maintenance by The Pool Butler. Contact us today to find out more about how we can take the work of pool cleaning.

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