Swimming Pool Winterization
By John Puetz
Keeping pool water clean, clear, healthy and inviting to bathers seems to carry its own rewards when the weather is warm and sunny. However, when the cool winds of autumn start to blow, it seems to be harder to think about pool care. This article will explain the process of winterizing swimming pool water, as proper care in closing the pool will not only serve to protect your client’s investment, but will hopefully make the task of opening the pool the following spring relatively simple.
Be proactive in the fall
If you are in the service/maintenance industry and depend on opening/closing pools as a portion of your livelihood, it makes even more sense to do as much as possible in the fall. Think about it; in the fall you will likely have more time at your disposal to close pools and no one is likely to be pressuring you to get the job done. The more you do now and the better you do it, the pool will be much easier to open in spring when customers are anxious to start swimming.
The approaches to pool closing vary widely. Some parts of the country experience severe freezing temperatures in the winter, while others remain fairly moderate and even warm. Pool construction also varies, from plaster to vinyl to fibreglass, while some are above ground and others inground—each has its own closing quirks. Service people also vary in their approach to winterizing. However, regardless of the location, pool type or approach taken, closing will provide clean water in the spring if done properly.
This article cannot cover all pool closing variations, but it will provide an overview of the essential stages of winterizing, along with the products that can be used to help make the task easier and more reliable.
Two areas of concern
Before any type of water treatment is performed, the pool should be given a thorough cleaning and prepared for winterization. In this process there are two basic areas of concern.
The first is to protect the plumbing and equipment from cold weather damage, especially in severe winter climates. To prevent freeze damage, care must be taken when draining water from the pool’s plumbing and equipment. How this is done will vary widely depending on pool type and the equipment itself. In general, you will want to blow out the lines and drain water from all pumps and filters. Once the lines are clear, specialized antifreeze (which is safe for pool use) can also be used to prevent plumbing lines from freezing; however, this approach is somewhat controversial. Some argue that if you empty the lines completely, there is nothing to freeze and thus cause harm, while other professionals swear by antifreeze, as it is a way to be certain any residual water that freezes will not cause any damage.
The second concern is to keep the pool water algae-free and as clean as reasonably possible.
Balancing the water chemistry is extremely important when closing the pool for the winter. It is best to adjust the water into the following ranges:
- pH, 7.2-7.8;
- total alkalinity (TA), 80-150 parts per million (ppm); and
- calcium hardness, 150-400 ppm.
It is not unusual to have calcium hardness levels higher than 400 ppm and it is not always easy or necessary to lower this level if it exceeds this range. It is always best to use a sequestering agent, regardless of calcium level, but especially if hardness is high. See more information on sequestering agents under step five.
Vacuum all loose debris lying on the pool floor, including leaves, bugs, pine needles, etc. If debris is left to sit over the winter, it may lead to staining or discolouration, which can be difficult to remove in the spring. This is also a good time to clean the tile line to remove any buildup of scum and scale. Minerals and oils are also easier to remove at this stage and will leave the tile clean, so only a light brushing is required in the spring.
After vacuuming the pool, but before draining the plumbing, it makes good housekeeping sense to clean the filter. A season-long buildup of oils, grease and minerals will have likely left the filter quite dirty. You can leave it until the spring, but cleaning it now means avoiding possible damage to the filter media and less work down the road. If left to sit over the winter, problems such as caking (sand hardening) in sand filters or buildup on cartridge media can occur.
When cleaning the filter, it is best to use a cleaner made specifically for pool filters. Muriatic acid can help remove mineral buildup, but it is not sufficient at removing oils and grease. A good filter-cleaning product should contain surfactants for stripping oily waste and acids for removing minerals in a single step.
While sand filters are particularly prone to caking and clogging with contaminants, cartridge and diatomaceous earth (DE) filters also benefit from waste removal. Allowing oily wastes to sit over the winter allows them to deeply set into the filter media only to cause grief in the spring. Clean the filter now and you will be thankful you are not facing a more difficult task later.
After the swimming pool and filter is cleaned, disconnect and drain all water from the plumbing and equipment. Remove and store pool parts, such as skimmer baskets, ladders, wall fittings, etc. This process will vary by pool type, based on professional advice. At this point, it is also a good time to inspect all equipment for signs of damage or wear and repair/replace any worn-out items. Your customers will thank you for taking care of these things.
At this stage, it is time to turn your attention to keeping the water clear, clean and trouble-free. Everyone knows the importance of keeping the pool free of algae. No one wants to pull back a pool cover and be faced with a swamp instead of a nice clean pool. While keeping the pool free of algal slime over the winter is obvious, you should also be concerned about keeping the pool walls free of stains and scale, which can cause corrosion.
If the pool will be covered for the winter with a solid cover, treat the water first with either a chlorine or non-chlorine shock. This will destroy any remaining organic material that may be in the water. If the pool was not treated with chlorine for a lengthy period prior to winterization, you may want to use chlorine to shock the pool, as this will kill any remaining organisms in the water. However, if a chlorine residual is present at the time of closing, it may be better to use a non-chlorine shock. Both will do an excellent job of removing organic matter that could serve to feed any algae that may get into the pool. It is not necessary to shock a swimming pool that will remain uncovered over the winter or use a mesh cover. In this case, the benefit of shock treatment is quickly lost, as organic matter can easily return to the pool via rain or falling debris.
Shocking the pool alone will not prevent algae from causing you grief. The best program is long-term control using a good winterizing algaecide. An effective algaecide can be specially formulated for treating pool water over the winter, or use one known to provide long-lasting algaestatic (prevents growth) activity.
Finally, you want to keep the pool walls and floor free of stains and scale formation. To do this, apply a sequestering agent that is formulated to control metallic stains (e.g. iron or copper) and scale formation. Sequestering agents also provide an added benefit by forming a film on metallic equipment, which helps prevent corrosion (oxidation and pitting), while also limiting chemical degradation (etching) on plaster.
You may think our work is done after installing the cover, which, to a large extent it is. However, it is also beneficial to periodically check on water conditions in late winter or early spring.
Evidence of algae growth or locating problems with the cover at this point will help you prevent finding a surprise later, when it is time to open the pool. Problems with the cover may be something that can be easily corrected; should you find algae starting to appear, you can apply another dose of algaecide to keep the problem in check. Even though the water may be very cold, algae can still grow.
Following these steps in the fall will make your client’s life easier and enjoyable come spring. If done right, you will be more likely to pull back the cover in March to find the water in good shape, minimizing the amount of work needed to get swimming.