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How To Protect Your Pool From Freezing

how to protect your pool from freezing
How to winterize a swimming pool is a subject that I have talked about extensively through the video series on winterizing pools as well as through the articles common pool closing mistakes as well as items you need to winterize a pool. I also have a more in-depth article about what I have learned over multiple decades and thousands of pool closings (and openings) about how to close your pool and open to crystal clear water next spring.


In total there is a TON of great information in these articles that will help you to better understand the pool winterizing process, component by component, as well as giving you the benefit of my experience when it comes to how pools need to be closed in order to make the start up process in the spring as easy as possible.


In an effort to continue to add to these resources, this article is intended to help you to take additional steps to protect your pool from freezing temperatures. Perhaps this is your first winter with a pool, or your area is expected to have record low temperatures, and you want to understand more about IF your pool were to break from freezing...how would it break? Where would it break, and more importantly, is there anything you can do to try to prevent this damage from happening? As a pool specialist that lives in a vast, frozen wasteland (Ontario, Canada) for six months every year, you can bet that my pool does not sustain any winter damage. Here are some of the additional steps that I take that not every pool owner does.





How To Protect Pool Pipes From Freezing

how to protect pool pipes from freezing
One of the greatest concerns for freezing temperatures and swimming pools is the plumbing installation. Any defects in the plumbing system, such as a leak, is certain to cause problems for the pool as well as long term damage to the property and pool deck. If you fail to winterize your plumbing system correctly then it is not guaranteed to break and start leaking...but the chances are awful high.


The standard way to deal with this problem is to evacuate all of the water from the plumbing system. If there is no water in the pipes, then the water will not be able expand and damage the plumbing. Of course, nothing is ever as easy as it sounds. Can you really be sure that you got 100% of the water out of your plumbing lines? Even 1% water that is left in the pipes can accumulate in the lowest area of pipe such that it fills the pipe interior. When it freezes this section of pipe shatters. Even though 99% of the water was removed from the system, the inefficiency in your process and the 1% remaining water is enough to cause a failure. Big crack, small crack - it is all the same. Now you need leak detection services and location / repair services...after you run your pool for a while and notice that something seems to be wrong. So what can you do to avoid this?





This 3 HP Blower is an example of what a pool service technician would use to blow out the water from the plumbing lines of the pool. It can be tempting to blow out your pool plumbing lines with a leaf blower, or wet/dry shop vacuum, but the reality is that they lack the power to reliably evacuate the water from your plumbing system. Consider this tool the minimum price of entry if you want to be sure that you are really blowing out all of the water from your system.


In some pools, and in some pipe configurations, using a lesser-powered blower might get the job done. Might does not cut it in my world and certainly not when it comes to winterizing pipes. Even with this equipment, which I consider to be the best tool on the market for blowing out lines, still sometimes it barely has the strength to get the job done - specifically when you start talking about air-locking a main drain, or blowing out a skimmer that is full of water.


Water is super heavy, and you can hear this powerful air blower bog down under the load when you try to blow out a skimmer that is full of standing water. The skimmer body is only 18" to 24" deep in most cases, plus the weight of the water in the pipe, and the blower really has to work to get that initial blowout from the skimmer. As you can imagine, if you are attempting to blow through a pipe that exits into the floor of a pool, six, eight, or even 10 feet deep, most blowers are not even going to come close to pushing the water out. But here is the big problem...you are not going to know. You do not close hundreds of pools like I do every year, and it might seem to you like you were able to blow enough air through the pipes, but you might not have. I guess you will just need to wait until spring to find out. I don't like guessing. As a professional contractor my solutions need to work and I have to stand behind them to retain my reputation. The first step in achieving the confidence you need to do this is choosing the right tool for the right job.


Air Locking Main Drains - As mentioned above, in some cases air-locking a pipe is the best that you can hope for in terms of winterizing. For example, you can blow through the main drain pipe in some plumbing configurations, but how can you plug that pipe so it does not fill with water as soon as you turn off the air? The answer is, in many cases, you can't. Air-locking a main drain can be simplified with the example of a straw and a cup of water. If you put the straw into the water, the straw fills with water as you lower it in, however, if you were to cover one end of the straw with your finger before lowering it in, no water will go into the straw. If I have a main drain pipe from my pump to the main drain, and that pipe has an isolation valve on it, you can blow out the pipe and quickly close the valve. This, in theory, air locks the main drain pipe. In theory. In reality the pipe system would need to be 100% leak free as any imperfections in the closed loop plumbing system would allow the water to fill the pipe back up (at least to the water level in the pool).


Skimmer To Main Drain Pipe - The equalizer line, or the non-pressure line that connects from a pool skimmer to the side port of a main drain in the bottom of a pool, is probably the hardest individual component of a typical pool to winterize. Firstly, not all pools will have this exact pipe configuration. Many will have individually run and valved pipes...which is better. But there are a LOT of pools, especially entry level vinyl liner pools, which have a pipe that connects the front port (one of two ports) in the bottom of the skimmer to the main drain. Blowing through this line will not allow you to air lock it as you can not isolate the pipe fast enough after pressurizing. You can't plug the other end unless you swim down to the main drain, which I hope nobody is doing, and so this one pipe is a common problem, and a known leak point in this pool type (in cold climate areas, of course). So what can you do in this case? The skimmer gets blown out through the back port and plugged with a gizzmo. At this point you can pour 1L of pool antifreeze down the front port. The main drain is open, and as such the heavier-than-water antifreeze will leak out at the main drain. The hope is that some remains in the upper pipe section where the rate of diffusion with the rest of the pool water is near zero. Finally, foam rope is added to the equalizer pipe before it is capped with a winterizing plug until spring.


Foam Rope In Pool Pipes - The big takeaway here from this section on protecting pool pipes from freezing is certainly the foam rope. Foam rope is cheap and readily available. You might have some already and know it as backer rod, which is used to fill large expansion joints before filling with a flexible sealant like silicone or urethane. In a pool plumbing system this stuff represents the last bastion of hope against frozen pipes. As illustrated above with the equalizer pipe, not all parts of a pool plumbing system can be easily protected from freezing damage. Or even if you did blow out the pipes properly, what happens if a winterizing plug falls out, or you have a crack in a pipe somewhere that lets ground water leak into and fill the pipes back up? Using foam rope at every opportunity is a great idea to help protect the pool system. In a worst cast scenario where water is trapped in the pipes, whether from failure or improper winterizing, then freezing water will crush inwards on the foam rope, instead of outwards on your plumbing pipe. Try to use rope that is at least 1/2" to 3/4" in thickness for maximum protection, and you can sleeve long sections of it (12" to 18") into pipes by twisting it as you push it in. It will hang up on the fitting flange but as you rotate it will slip past. You do not need to worry about losing it in the pipes since it floats and will readily come out of vertical pipes on its own. On horizontal pipes like returns simply remember to pull it out in the spring before you put the return eyeballs in place!





What makes this backer rod specifically good for this application is that the foam is a closed cell foam product. Closed cell foam means that the cellular structure of the foam is not able to absorb water. This is critically important as open cell foam would slowly become waterlogged over time and would lose the ability to provide protection from freezing. I like to replace my foam rope every year or two as it begins to take on water and you can feel it is heavier than it was when it was new.


Some pool technicians might charge the plumbing lines with antifreeze. If you want to do this then I suppose there is no problem...as long as you have a good way to keep as much of the antifreeze as possible out of the pool water come spring. This is the main reason that I don't charge lines with antifreeze. I am very confident with my ability to evacuate the water from a plumbing system, and ensure that the right plugs are used, along with a reliable thread sealant. If you want to go the extra mile then there is nothing wrong with being too careful, but in my experience antifreeze in all of the plumbing lines is not required for winterizing pools even in the coldest of climates.


How To Protect A Pool Skimmer From Freezing

how to protect a pool skimmer from freezing
Whether you have an entry level above ground vinyl liner pool, or a world class inground concrete pool, having a skimmer crack from freezing damage is a huge pain. Skimmers on all pools are notoriously hard to fix. Once yours cracks you probably will need a new one, and that also is a notoriously difficult repair. A vinyl pool would often need a new liner in order to replace the skimmer, and the older the liner is the more likely this will be the case for you.


Concrete pools usually have the skimmer encased on all sides in a giant cube of concrete as this permanently anchors the skimmer to the side of the pool. If you need to replace your skimmer then you will need to remove this buried cube of concrete, and then replace it again when you are done changing the skimmer. Here is an example of how to change a pool skimmer.


Protecting The Skimmer Pipes - For these reasons, no matter what kind of pool you have you simply must take all steps possible to protect the skimmer from freeze damage. The first step in this process is to drain your water level in your pool such that you can remove all of the water from the skimmer, and skimmer pipes, such that you can get right in there and work on it without water in the way. Above ground pools will be much more straight forward in this regard. Inground pools often require the skimmer to be blown out in stages, usually by plugging the front hole (equalizer line) temporarily while you blow from the pump through the rear port on the skimmer. Both ports need to be sealed with winterizing plugs, or preferably a gizzmo, but before doing so I like to add about 1L of pool antifreeze to each port. This is just for an added layer of protection should something go wrong with my winterizing process, or with the pool itself over the winter. I usually do not do the same for any return pipes.


Protecting The Skimmer Body - After the antifreeze I would then thread at least 12" of foam rope into each the front and back ports on the skimmer. Only then would I add the gizzmo or plugs to the bottom. This accounts for the pipes themselves but does not address that the skimmer itself may fill with water again once the water level in the pool rises and overflows through the skimmer throat. For this reason I like to add about 2L of antifreeze to the bottom of the skimmer. Usually when closing a pool I will also be adding a chemical closing kit with algicide and oxidizers and all of the empty bottles I end up with get stuffed into the skimmer body. A sealed bottle will provide something for freezing water to crush instead of pushing outwards on the body of the skimmer. If I wanted to get as technical as possible, a 2L plastic soda bottle, washed and filled half way with pool antifreeze would be ideal. The bottle is large and would sit nicely inside a skimmer body. Filling it with a liquid means it will not simply float on top of the water, but will instead remain neutrally buoyant should the skimmer body fill with water before spring.


When you put the lid back on top of your skimmer I like to first put the lid into a plastic bag so that I can effectively close the finger hole in the center of the lid. This will discourage run off and rain from filling up the skimmer body with water any sooner than it needs to from the rising water level in the pool. Even if you use an isolation cover like a tarp on your pool, the water level will still get forced up to the skimmer throat from the weight of the water on the cover (from rain) displacing water that is in the pool.


Tips For Avoiding Freeze Damage

tips for protecting your pool from freezing
When you winterize your pool equipment you will be removing 100% of the water from them such that it is not possible for them to break in the winter. Since your plumbing system is below ground it would be much harder to remove all of the water with the same degree of confidence as something above ground that is much easier to blow through. For this reason, pool equipment does not require special considerations in very cold weather over and above what is considered standard for pool equipment winterization.

If this is the subject that you are looking for more information on then you will find a detailed discussion on each piece of equipment in my video series on winterizing pool equipment.


Cracks In Pool Decks - When it comes to the pool itself there is one, great big, giant, potential problem that is lurking that all pool owners need to be on the lookout for - cracks in the pool deck. Any place where your pool deck (or pool coping on concrete pools) has cracked, water is now able to access some place where it should not be. If you happen to live in an area where freeze and thaw cycles are common, or any place where freezing temperatures can happen for that matter, then any water inside this crack will expand when it freezes. This causes the crack to get wider, deeper, longer and can also cause the entire area of deck to heave upwards. Having exposed cracking in your pool deck is a huge liability in cold climate areas and easily one of the most overlooked and easily fixable problems. Simply use a concrete urethane sealant to seam any cracks that you have in your pool deck to minimize further problems from freezing water.


Pool Winterizing Plugs - How much thought have you put into your pool winterizing plugs? I am going to guess not very much. There are really only a handful of styles that are commonly used such as rubber winterizing plugs and threaded winterizing plugs, and then variations on these styles (as well as some newer plugs like "duck plugs" for blowing out lines underwater). One of the most overlooked aspects of winterizing a pool is that if your plugs fail, then you have failed to winterize the pool. When using threaded plugs, which is what I suggest all pool owners use, you must understand how teflon tape works, and you must wrap the plug threads in the correct direction or the tape will simply come off as you tighten in the plug. When applied correctly, the threads will help to wrap the tape even tighter around the plug as you tighten it in place. The reason why expandable rubber winterizing plugs are not recommended is because they can get ripped out of the return. Even if tightened thoroughly, as the water level in the pool climbs it is possible that the plug can get grabbed by ice on the surface of the water. If this happens the plug will rip out of the return as the water level in the pool rises over the winter. To avoid this, use threaded plugs and be careful about how you apply the thread sealant tape. If you need more information on thread sealants and pipe threads for pool systems you can read this article on PVC thread sealants for pools.


Pool Equipment Winterizing Series

Items You Will Need To Winterize Your Pool

How To Open Your Pool To Clean Water Next Year

Common Pool Winterizing Mistakes






Swimming Pool Steve

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