Closing time: Techniques for ‘hard’ or ‘soft’ winter pool shutdowns

by habiba_abudu | September 26, 2019 11:25 am

By Terry Arko

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As the swimming season begins to wind down, it is once again time for service professionals to get pools ready for closing. Depending on the region and climate, winterizing a pool can vary between a ‘hard close’ and ‘soft close.’ Whether one is shutting down and preparing for an extended period of deep freeze, or just reducing filter runs and covering the pool, the following are some tips on methods and products, which will allow service techs to perform these tasks successfully.

A hard close

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The first step is getting the water ready not only for the winter, but also the pool’s eventual opening the following spring. Yes, service techs must always think ahead. How the water is prepared at closing will play a significant role in its quality when the pool is opened. Therefore, pool professionals should perform the following recommended tests before closing: metals, all water balance values (i.e. pH, total alkalinity, calcium hardness, and total dissolved solids [TDS]), and phosphate levels.

In areas where metals are a problem, service techs should add an ethylenediaminetetraacetic acid (EDTA)-based sequestering product first. A few hours after administering, the water balance can be adjusted to the ideal ranges. The best scenario is to adjust the water balance using the Langelier Saturation Index (LSI).

One precaution, however, is to never add sodium carbonate (soda ash) or sodium bicarbonate (baking soda) on the same day as calcium chloride (calcium increaser). Doing so will cause immediate formation of calcium carbonate scale on the pool surface. Once the water is properly balanced, chlorine can be added. Shocking the pool with at least 20 parts per million (ppm) of liquid chlorine is recommended, as this will not contribute any additional calcium mineral or cyanuric acid (CYA).

After several hours, if desired, a clarifier and enzyme product can be added to the pool. A good polyquaternary algaecide should also be administered. If a copper algaecide is used, make sure it is a low percentage copper sulfate pentahydrate complex, which is usually guaranteed against staining under normal pool balance conditions. If staining is a concern, a quaternary algaecide should be used.

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The pool water should be allowed to circulate for several hours after adding the algaecide. Following this, if a CYA stabilizer is needed, it can be added at this point. Normal levels of CYA stabilizer are between 30 and 50 ppm. For winterizing purposes, these levels may be run lower as the pool will be covered, and the water temperature will be low. Once the pool is opened in the spring, additional CYA stabilizer can be added at that time.

High phosphates can lead to water quality issues when it starts to warm up in the spring. Therefore, service techs should be proactive and lower the phosphate levels to at least 500 parts per billion (ppb) or lower before closing the pool. The use of a good phosphate remover will lower the levels of phosphate in the water to ensure better results at spring opening. This is the final step in preparing the water for its winter hibernation.

After treating the pool, the water level must be drained below the skimmer. The following are some suggested water levels for different pool types:

• Vinyl liner: 25 mm (1 in.) below the skimmer opening (lower in areas where heavy snowfall or rain is experienced);
• Plaster finish with solid material cover: 25 to 152 mm (1 to 6 in.) below the skimmer opening or tile line (whichever is lower);
• Painted or natural finish with solid material cover: 152 mm (6 in.) below the skimmer opening;
• No cover or mesh cover: 457 to 610 mm (18 to 24 in.) below the skimmer opening; or
• Automatic cover: no lower than the bottom of the skimmer opening.

Here, the main concern is to ensure water does not re-enter the skimmer as it will freeze and cause damage to the skimmer well and plumbing. There are skimmer devices that can be added if the plumbing lines are treated with pool antifreeze. These devices can protect the skimmer from freezing should water re-enter. Partial or full draining of a pool at closing could lead to damage in high water table areas due to hydrostatic pressure upon the pool.

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If the pool is to be drained completely for the winter, service techs should ensure there is a functioning—manual or automatic—hydrostatic relief valve installed on the pool. It is designed to allow some groundwater to seep back into the vessel and relieve the pressure. If the pool is not equipped with a hydrostatic relief valve, it is not advised to drain all of the water upon closing as groundwater pressure could cause the pool to shift or pop out of the ground. Completely draining inground vinyl-lined pools is not recommended. Doing so can lead to displacement and shrinkage of the liner. Above-ground pools should only be drained below the skimmer and winterizing pillows or floats should be used to prevent damage from contraction and expansion. The sides of an above-ground pool should also be reinforced to prevent them from collapsing.

When draining pool water, service techs should know what the municipality bylaw is. In many areas, pool water must be dechlorinated. One of the best ways to achieve this is to stop chlorinating the water for several days, which would allow the levels to decrease naturally. If that is not possible, the pool can be quickly dechlorinated using sodium thiosulfate. It takes approximately 25 g (0.9 oz) of sodium thiosulfate to remove 1 ppm of chlorine in 10,000 L (2642 gal) of pool water.

Finally, service techs should use an air compressor (or shop vacuum in reverse) to clear all the lines and plumbing of water. Standing water should be removed from the suction lines, such as the skimmer and main drain, as well as the returns and any plumbing leading to the pool equipment (e.g. heaters, automatic cleaners, and water features). The skimmer and both return and vacuum lines should be closed off with expandable rubber winterizing plugs. A non-toxic winterizing antifreeze can be used prior to sealing the pipes.

There are many pool antifreeze products available that can be added into the skimmer above the plugged lines. It takes approximately 3.78 L (1 gal) of pool antifreeze to treat 3 m (10 ft) of 38-mm (1.5-in.) pipe. Service techs should never use automobile antifreeze as it is toxic and will damage some types of plumbing. Also, pouring antifreeze into the pool water is not advised as it will be diluted to the point where it has no effect.

Winterizing equipment

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All ladders, diving boards, and handrails should be removed, cleaned, lubricated, and stored in a cool, dry area. To prevent rust and corrosion, all equipment should also be thoroughly drained, cleaned, lubricated, and stored in a warm, dry place. This includes pumps, filters, heaters, and chemical feeders.

Special care should be taken for parts such as lint pots, baskets, plugs, O-rings, gaskets, valves, and pressure gauges. A good practice service techs should follow is to use an anti-rust lubricant and store any loose parts in sealed bags. Further, creating a checklist and inventory of all the parts and equipment that have been stored certainly comes in handy when it is time to open the pool. Everything should be stored in a secure area safe from vandals, rodents, and insects. It is paramount to keep all equipment free of moisture during the winter.

Pool decks should also be cleaned thoroughly, and all expansion joints and any cracks should be caulked and sealed to prevent damage from freeze-thaw expansion.

Pool lights need to be protected from freezing and deterioration, too. If the lights are less than 457 mm (18 in.) from the water surface, they must be removed from their niche, weighted down, and gently lowered to the bottom of the pool. Ideally, if possible, they should be removed, lubricated, wrapped and stored in a box in a warm, dry storage room. Service techs should take special care if the light is left on the deck. The power must be turned off and (preferably) the breaker switch should be tagged and locked to prevent anyone from turning the light on while it is out of the water. If a light is powered on while it is out of the water, it could lead to an explosion leaving shards of glass throughout the area.

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Pools should be covered to protect them from dirt, debris, leaves, or other objects while it is closed. Most winter covers are secured to the deck around the perimeter by spring loaded fasteners. Service techs should inspect and lubricate these fasteners to protect them from corrosion or breakage during the winter. Some covers allow rainwater to pass through into the pool. In this case, the pool should be checked regularly during heavy rainfall to ensure the water level does not rise over the skimmer opening.

Solid covers can collect rainwater on the surface, which could lead to damage and/or pose a drowning hazard for young children who gain unauthorized access. Therefore, a sump pump should be employed to vacate any water accumulation. A good practice to follow is draining all water from the cover within 30 minutes after the cessation of a rainstorm.

A soft close

In milder climates, pool water should still be prepped similar to a hard close. That said, service techs should add a metal sequestering agent and balance the water in accordance with the recommended ranges. Next, the water should be superchlorinated using liquid chlorine for quick oxidation and good residual without increasing calcium or CYA levels. The use of water clarifiers and enzymes in a soft close situation can be quite beneficial as this will help to break down and minimize small micron organic particles. Also, they will act as filter cleaners and aids when the circulation time is shortened for the off season.

Following this, an algaecide should be added and allowed to circulate throughout the system. Then, CYA levels can be tested and adjusted as needed. Finally, service techs should check the phosphate levels and ensure they are capable of being maintained below 500 ppb. When performing a soft close, turn off the heater and allow the water to circulate for a few hours—preferably at night or during a cooler period. In the case of an expected freeze, or during freezing periods, the pump should be allowed to run for 24 hours until temperatures return above freezing. During this period, a service tech should inspect the pool and test the water at least once per month throughout the off season. In cases of extended warm weather, chlorine levels should be checked at least twice per month and adjusted appropriately. An additional dose of algaecide may be necessary during a warm, mild winter.

Covers can help keep debris out of soft close pools as well; however, as these maintenance checks are performed more frequently, they can make them more of a chore. Ideal covers for soft close pools include: automatic or those on a reel, which makes removal and replacement easier. On pools equipped with mesh covers, service techs will need to ensure the proper levels of CYA stabilizer are maintained, while also frequently checking for correct chlorine residual and water balance.

Saltwater generators

When servicing pools equipped with salt chlorine generators located in regions that experience mild climates, techs should set the unit to neutral or winterize. In hard close areas, the generator cells should be removed, cleaned, and stored in a secure, dry area. Techs should also ensure power to the unit is off. The water should be prepped in the same manner as regular pools for metals, chemical balance, algae prevention, and phosphate removal. Further, as discussed earlier, the water should be drained to the levels in accordance with the pool type, and in a manner that abides with municipal bylaws.

Some jurisdictions have strict regulations for draining pools equipped with salt chlorinator generators. In this case, pool water cannot be drained into catch basins (i.e. storm drains). Instead, it is recommended the water be disposed of in one of the following ways:

• draining the water to the wastewater sewer (not the sump pit);
• draining the water onto the client’s lawn; or
• hiring a licensed wastewater hauler to remove the water.

Whether a service tech is performing a hard or soft close, it is important for one to remember that the due diligence taken at closing time will pay off the following spring when they are opening the pool.

The correct sequence for chemical adjustments

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Time should be allowed when winterizing a pool and preparing the water for closure. Chemicals should not be added all at once and never mixed together to save time. The following is a handy list for service techs in regard to the proper sequence for adding chemicals:

1. Chelating or sequestering agents (preferably EDTA or non-phosphate products)
2. Alkalinity adjusters
3. pH adjusters
4. Calcium hardness increasers
5. Chlorine compounds
6. Water clarifiers and enzymes
7. Algaecides
8. Cyanuric acid
9. Phosphate removers

The Langelier Saturation Index explained

The LSI is a method for determining the concentration of calcium in pool water. It is used to establish the potential for water to be either scale forming or corrosive. Since temperature plays a role in balanced LSI, it is vital the pool LSI remains as close to perfect as possible.

Cold temperatures can lead to corrosion and as the water begins to be heat up, it can start to precipitate calcium as scale. There are many tools available for service techs to calculate the proper LSI. In fact, most test kit manufacturers include LSI information in the kits. Also, there are now several smartphone apps available to help determine and adjust LSI.

Target ranges for water chemistry

Robert W. Lowry is an authority on water chemistry and has more than 45 years of experience in the pool industry. He recommends setting ideal targets for water chemistry adjustments rather than settling for just the minimum or maximum levels. In his book Pool Chemistry for Service Pros 2018, Lowry points out if water balance levels are all at the minimum acceptable ranges, the water is going to be corrosive. Conversely, water balance that is at the maximum level will be scale forming. That said, he recommends the following ideal target levels to achieve perfectly balanced water:

• pH: 7.5
• Total alkalinity: 90 ppm
• Calcium hardness: 350 ppm for plaster pools and 250 ppm for vinyl pools
• Total dissolved solids: no more than 2000 ppm over startup. If the water in the pool is 2000 ppm over what the source water is, TDS from the pool should be tested, and then from the tap, and compare the two.
• Cyanuric acid: 50 ppm

[8]Terry Arko is a product training consultant at HASA Pool Inc., a manufacturer and distributor of pool and spa water treatment products in Saugus, Calif. He has more than 40 years’ experience in the pool and spa/hot tub industry, working in service, repair, retail sales, chemical manufacturing, technical service, commercial sales, and product development. He has written more than 100 published articles on water chemistry and has been an instructor of water chemistry courses for more than 25 years. Arko serves as an observer on the board of the Recreational Water Quality Committee (RWQC) and is a member of the Council for the Model Aquatic Health Code (CMAHC). He is a Commercial Pool Operator (CPO) course instructor, a teacher of the Pool Chemistry Certified Residential course for the Pool Chemistry Training Institute (PCTI), and a member of Pool & Spa Marketing’s Editorial Advisory Committee. Arko can be reached via e-mail at h2owrite@gmail.com.

References:

• Association of Pool and Spa Professionals (APSP) Service Tech Manual 4^th Edition 2010-2013.
• National Swimming Pool Foundation (NSPF) Pool & Spa Operator Handbook 2017.
• The Complete Swimming Pool Reference, Tom Griffiths, Mosby Inc., 1994.
• Pool Chemistry for Service Pros by Robert W. Lowry, Lowry Consulting Group LLC ©2018.
• Certified Pool-Spa Operator Course Supplemental Information, Leslie’s Swimming Pool Supplies 2017.

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