How to Clean a Pool That Has Been Sitting? [Concrete, Fiberglass, Vinyl, Saltwater]

As the heat of summer approaches, we think about the joys of hanging out at the pool: the cool blue water, splashing kids, lounge chairs, and slushie drinks. But what if your pool has been sitting neglected? It’s half-full of slimy green water, mosquitos, and leaves. There may even be some tadpoles hanging out in there. So how do you get that pool ready for summer fun?

The best way to clean your pool is first, remove the organic matter with either a pump or nets, then scrub and vacuum any remaining debris. Finally, treat the water with chlorine, algaecide, and stabilizers. These are the basic steps for any pool.

However, you do also need to consider what the pool is made of because the material can change how you clean it. You should also check for any required repairs or leaks and take care of those before trying to get the pool summer-fun ready.

We have detailed instructions for each kind of pool so you can take care of the cleaning and get on with the summertime fun.

Concrete Pool

Besides becoming a fascinating study in how swamp life develops, a pool full of organic material, algae, mosquitoes, and frogs can damage the pool’s interior surfaces. If your pool is concrete, it is a sturdy structure in the ground, and you can safely drain it so that you can clean it thoroughly. Once you drain a pool, take care of the cleaning and repairs quickly and refill it so that the pool’s structural integrity remains intact.

Draining The Pool

First, decide if it is essential to drain the pool. If you can clean out the leaves and branches with nets, this is a better choice for the structural integrity of your pool. Then, determine a good time to drain the pool. You should only drain the pool if the ground around it is dry. If the soil is saturated and you remove the weight of the water from the pool, even a concrete pool could rise out of the ground.  

If there is a great deal of organic matter, like leaves, twigs, and branches, you can rent a 2″ or 3″ trash pump. These are strong enough to pick up objects that are the size of golf balls, so you will still need to remove any large objects from the pool with nets. Be sure that the drain hose is far away from your pool so that the ground around it does not become saturated with dirty water.

Cleaning The Pool

While the pool is draining, you should scrub the sides to remove any algae or other organic matter stuck to the sides. It will be much harder to remove once it dries in the hot sun.

Once the pool is drained, you may need to acid wash the pool to remove any stains. This process should not be done annually because the acid eats away at the plaster coating of the pool. Acid washing the pool is a multi-step process that needs to be undertaken with care.

Be sure to read up on the process and how to complete it safely. It is better to maintain the pool throughout the year so that this step is not necessary.

How to Clean a Pool That Has Been Sitting

Evaluate For Repairs

Concrete pools have two layers. First, you can see the plaster coating on the inside, and then there is the concrete that is the pool’s structure. Cracks in the plaster layer don’t threaten the structure of the pool, but they can contribute to problems with algal growth because algae can get into the small cracks. You may be able to patch the plater yourself, or you can call a pool repair specialist to fix the damage.

A crack in the concrete of the pool will look much deeper than a plaster crack. You might also notice that you have to refill the pool frequently. If you have a structural crack, you should contact a pool construction specialist to repair it.

Refill The Pool

Once you have drained, cleaned, and repaired the pool, you are ready to refill it and treat the water. Add the appropriate amount of chlorine or salt depending on your pool system and maintain the proper pH balance in the pool.

Fiberglass or Vinyl Pools

Fiberglass pools or those with a vinyl liner are not as structurally stable as concrete pools. Therefore, it is better to keep these clean so that you do not have to drain them, but if you find yourself with a particularly dirty pool that has been sitting unattended, you may need to drain it.

Draining a Fiberglass Pool

Because these pools are very light and vinyl liners may tear, draining, cleaning, and refilling the pool should be done quickly to maintain the pool’s structural integrity. 

Before draining the pool, ensure that the ground around it is thoroughly dry. Don’t drain the pool after heavy rains because the land will be saturated with water. Once you drain the pool, it will be much lighter and might be forced up out of the ground if the earth is saturated.

Also, be sure that the drain pipe from the pump is far away from the pool and the land around it. You don’t want to remove the water from the pool just to saturate the ground with dirty water.

Cleaning Fiberglass or Vinyl Pools

Once the water is out of the pool, use a low-pressure cleaner, mild soap, and a soft brush to clean any algae or other material stuck to the pool’s surface. You will have more success if you clean it before it dries. It is easier to clean wet algae than hard, dried algae. 

Clean a Pool That Has Been Sitting

Check For Repairs

If there is a crack in the fiberglass pool, you can repair it with a little DIY ingenuity and elbow grease. You will need to sand the fiberglass around the crack, then enlarge it neatly with a diamond blade. You can purchase a repair kit that contains a bonding agent, polyester putty, fiberglass cloth, and a final gel coat. Follow the instructions on the repair kit to fix small cracks in a fiberglass pool.

Refill The Pool

Once you have cleaned and repaired the pool, you are ready to refill it, treat the water, and have some fun in the sun!

Cleaning the Water Without Draining the Pool

Whether you have a concrete, fiberglass, or vinyl-lined pool, you can clean the pool without draining it if it is dirty but not completely swampy. So how do you know which road to take? A good rule of thumb is if you can see the bottom of the shallow end of your pool even though it has been sitting, you don’t need to drain it. 

Remove Organic Matter

Use nets to clean out all the organic matter like leaves and twigs from the pool. Keep scooping until the nets come up clean. 

Balance the pH

First, you need to test the pH of the pool water. You should be testing the pH at least twice a week to ensure that it stays at the optimum level of 7.2 – 7.6. Maintaining the proper pH makes the pool comfortable for your family to swim in and also protects the pool equipment like the pumps and filters so that they don’t deteriorate. Furthermore, the chlorine you use in the pool will not work correctly if the pH is too high.

When pH levels are high, the water is alkaline (basic). To balance the pH, you need to add a mild acid. You should carefully follow the manufacturer’s directions, like wearing gloves and goggles, when using pool chemicals. Be sure to add the correct amount of chemicals based on the instructions. Then, wait at least 2 hours for the water to cycle through the filtration system. Finally, restest the pH, and if it is in range, you are ready to swim.

In some cases, the pH may be too low, meaning the water is too acidic. For example, pool parties, heavy rainfall, and many leaves can lead to low pH levels in a pool. It is also possible to overtreat a high pH and make the water a little bit acidic. 

You can raise the pH of your pool with sodium carbonate (also known as soda ash). You should follow the manufacturer’s instructions on the packaging. It can make the pool appear cloudy due to chemistry (literally the trading of hydrogen atoms), but that will clear as the water moves through the filter.

Add the Proper Amount of Chlorine

You will need to calculate the number of gallons of water your pool contains so that you can add the correct amount of chlorine to the pool. The proper amount of chlorine is 1-3 parts per million. It would be best to use pool test kits to check the levels of all the chemicals in your pool. 

Chlorine is available in tablets, granules, and liquid. You should always wear gloves and goggles when adding chlorine to your pool to protect yourself. Follow the manufacturer’s instructions on the packaging and never mix types of chlorine when adding it to your pool.

Chlorine tablets in a floating dispenser are an easy way to maintain the proper chlorine balance in your pool once you have reached the desired 1-3 ppm. It is safe to swim in a pool with a tablet chlorine dispenser. 

For best results, use a chlorine shock treatment on the pool every 1-2 weeks, depending on how often people swim in it. Shock treatments raise the chlorine level to 8-10 ppm, so it is unsafe to swim in the pool until the level drops below 5 ppm.

One way to get the most out of your shock treatment is to do it after dark. UV light from the sun breaks down chlorine and can make it ineffective. Always follow the manufacturer’s instructions when using a shock treatment for safety.

Saltwater Pools

Draining Saltwater Pools

If you need to drain a saltwater pool, you will need to check the city ordinances to see where you can dispose of the water. In some places, you can drain the salt water into the street, but not everywhere. The problem is that stormwater drainage systems from streets often go into wetland runoff areas. Water with high salt and chlorine content can cause damage to ecosystems downstream. 

If you have a large property, you can drain the pool onto your own land. Occasionally, this will not harm your ability to grow plants, but if you drain it frequently in the same place, the salt will become embedded in the soil, and plants will not grow.

The other option to drain a saltwater pool is to drain it into your home’s sewage system so that the water processes through the city’s water treatment plant. You will need to run the hose to the lowest drain in your house and go slowly so that you don’t flood your home.

If you live in a cold climate, you will need to close your saltwater pool for the winter. In addition, you will need to drain it partially each year to prevent water from freezing in the piping for the pumps and filtering system.

Cleaning Saltwater Pools

Saltwater can cause stains and scale build-up on pool surfaces. However, you can add enzymes to the pool water that reduce the likelihood of these building up in your pool. Check with your local pool maintenance company for more information. 

Balancing the pH and Chlorine in a Saltwater Pool

Saltwater pools are more likely to be alkaline (basic) than chlorine pools, so you will need to check and adjust the pH more often. 

Also, you might still need to shock the water in a saltwater pool to maintain the proper amount of free chlorine in the pool. 

Maintain the Pool

Taking care of a pool is a lot of work. You don’t want to go through clearing a pool full of standing water every year, so take some steps to maintain the pool throughout the year for the best results. 

Even in the winter, when you are not swimming, you should take care of the pool water and equipment to be in good shape for the spring. 

Keep the pool clean. Skim out any foreign objects like leaves and grass that blow into the pool. You may need to clean it more often in the spring and fall. 

Maintain the pool’s chemical composition throughout the year. The chemical balance in the pool is not just for your health and safety. It is also the optimum level for keeping pool equipment like pumps and filters working properly. 

On that note, run the pump for 8-10 hours each day to keep the water moving through the system. Clean or change your pool filters every 1-2 months based on the clarity of the water. 

Finally, cover the pool anytime you are not using it, even in the summer. It will help prevent evaporation and keep foreign objects out of the pool.

Final Thoughts

Regardless of the events that led to your pool sitting and becoming swampy, you can clean it for some summer fun in the sun. Clean out the debris with a pump or nets, make any necessary repairs, and treat the water so you and your family can swim safely. 

Now, put on your sunscreen and enjoy the summer!

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