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Pool Closing Tips For Clear Water In The Spring

Winterizing your pool, or closing your pool for the winter season is a subject that has been discussed in length online. I have also covered this subject in my Pool Winterization Video Blog where I discuss each part of the closing process in detail. Something that deserves an entire article dedicated to it, is how to close your pool so that the water is still clear when you open it next year.

pool winter cover
My experience in the pool and spa industry is largely in the construction side. Construction companies tend to stay away from service and maintenance work, of which closing the pool is part of this list and for much of my career I only closed a handful of pools each season. Also for much of my career I was located in Vancouver BC where you do not typically close your pool for the winter, instead heating it to a few degrees above freezing and run the circulation system year round.

So why am I writing this article on how to keep a pool clear and clean when you close it if I do not have much experience with closing pools? Well, I said I had worked largely on the construction side. From 2010 to 2015 I was actively involved with a large service and maintenance company in the highest pool density location in Canada. During this time as a team lead I was involved in closing just slightly over 7000 pools. Most of this was from repeat business so I was able to monitor this high volume of swimming pool closings the following spring when the pool was opened. From this experience I have learned some tips that you can use if you want to make sure your pool water is perfectly clean and clear in the spring.

Clean & Balance Your Pool Before Closing It!

green pool water
For some readers this information would hardly seem revolutionary. These same readers would be surprised to know that probably 30% of the pools that we arrived to close were already a deep, dark green color. Really? Yup. You would not think that a pool owner would let their pool turn completely green, and stop vacuuming it, before the service company is scheduled to come and close it...but they do.

When a pool company comes to close the pool for the year they can not resolve deficiencies in water chemistry properly before closing it. It will be closed green and it will be opened early in the spring looking like a bachelor apartment for Swamp Thing. When it comes to closing your pool you need to have the pool chemistry balanced and the water must be perfectly clean, clear and free of debris. Will a single leaf or two be enough to turn the pool green over the winter? Probably not, no. Just make sure that the pool has been vacuumed thoroughly, and run the filtration system 24/7 for a week leading up to closing it. The cleaner and more clear the water is when you close it, the better the pool will look when you open it - super simple stuff!

Pool Covers Affect How You Should Close Your Pool

Before we can even get into the specific steps you need to take to keep your water clean and clear over the winter we need to look at pool covers. There are quite a few different kinds of pool covers and you need to be able to identify yours and adjust your closing procedure accordingly. The most important factor to consider is whether the cover is a debris cover, or an isolation cover.

An isolation cover is designed to provide a complete barrier between the pool water and the outside world. No debris or water can pass to, or from, the pool water. This is the ideal type of cover if you want to keep your pool water clear over the winter. A debris cover is a pool cover that is designed to keep physical debris out of the pool, but still allows rain and snow melt into the pool. These types of covers make it much harder to ensure clear pool water in the spring.

Tarp & Water Bag Covers - This is the oldest and most common type of pool covers. It used to be that sand bags were used instead of water bags. Sand is a pain to get out of the pool when it falls in so eventually water bags took over the industry. It also used to be that water bags were made from thick, durable materials and would last for many seasons. Water bags that you purchase now are so cheaply made they have a 50% failure rate new, right out of the box from the manufacturer. If you can get even a few years out of a new water bag these days then you are beating the system. Tarps also are made thinner and thinner every year. They are at least much more affordable than they used to be, but they are also about 75% thinner material than they used to be. This cover system is an isolation system designed to segregate the pool water from both dirt and water contaminants. The problem is that once the cover tears then it is no longer working to isolate the pool water. All debris and water on top of the cover will be able to access the pool. If you have a tarp and water bag cover on your pool, and you have a hole in your tarp, then you will most likely have green and dirty water in the spring. Take care of your tarp and replace it any time you discover a hole. One of the best places to get a pool winter tarp cover is to order it online.

lock in pool cover Lock In Pool Covers - Lock in pool covers are most often used on vinyl liner pools. Similar to the track that retains the liner bead, pools that use these covers have a second track just above the liner track and this is where the lock in cover is installed. A lock in cover is sometimes confused with a deck mounted safety cover since the name itself, "lock in cover" sounds very secure. A lock in cover is not a safety cover and you should never attempt to walk on one. Lock in covers come in two material styles, one is vinyl just like the liner, and the other is lightweight like a tarp cover except it has a vinyl bead sewn on it. Lock in winter pool covers are also designed to isolate the pool water from both debris and water from rain or snow. Lock in pool covers are custom made to fit the exact shape and size of your pool. If you have a rip in your cover this will also most likely result in green water in your pool in the spring. The vinyl covers can be patched with a vinyl pool repair kit. The tarp style lock in covers are not able to be patched effectively.

mesh safety cover Mesh Safety Covers - The entry level deck mounted winter safety cover is a mesh material that allows water on top of the cover to access the pool water. This makes this cover a debris cover, not an isolation cover. Since water from on top of the cover can drip down into the pool but debris like leaves accumulates on top of the cover, you will end up with a tea bag staining effect in the water. These mesh covers also come in different quality and thickness of mesh. The thinnest of the mesh covers will allow up to 5% sunlight into pool. The best mesh covers allow only 1% of light into the pool. This is significant in both cases as the light will encourage algae growth. Also the cover will allow silt into the pool along with the water. This type of cover is very difficult to keep clean and clear over the winter season. The biggest tip to avoid this is to augment your closing schedule. A pool with a mesh safety cover should be closed as late into the season as possible, and opened very early into the year. Previous owners of isolation covers usually do not open the pool until they are ready to use it. If you change to a mesh safety cover you now should close the pool before you start to experience freezing temperatures at night - long past the point that you are actually swimming in the water. The same goes for opening in the spring in that you should open as soon as the freezing temperatures have stopped - long before it will actually be warm enough to swim. If you close your pool early and open it late with this type of cover then you are going to have green water, and possibly even neon green water.

solid safety cover Solid Pool Safety Covers - For around 50% more money than a mesh safety cover you can have a solid safety cover. A solid safety cover is not actually solid however it is not mesh, so more solid in that regard. A solid safety cover is an isolation cover and effectively separates the pool water from water and debris on top of the cover...usually. Solid covers usually have a mesh section in the deep end to allow snow and rain to melt into the pool. This prevents the weight of water on the cover from damaging it or the deck mounting hardware. A solid safety cover will be less inclined to allow the pool water to turn green over the winter than a lighter mesh cover however any water that is able to leak into the pool will carry contaminants. Contaminants and organic debris are what causes the water to turn green. If your solid cover has a cover pump then you can actively pump off the melt water and rain as opposed to allowing it into the pool. This would dramatically reduce the chances you open your pool to green water in the spring.

automatic pool cover Automatic Pool Covers - Auto covers for swimming pools are fantastic for many reasons such as improved chemical efficiency, improved heat efficiency, ease of use and most of all, safety. The only downside to an automatic pool cover, aside from the cost, is that they can't be used as a winter cover. Actually, should not be used as a winter cover would be more accurate. By using a pump to keep water from pooling on the cover you could,in theory, use an automatic pool cover as your winter cover. The problem is that the cover pump system is not perfect and it is easy for water to accumulate on top. The weight of snow load and water is simply no match for the system hardware and weight related failures are common. A big source of this problem relates to pools that area leaking, or develop a leak, over the winter season. If the water level drops then there is no support for the cover. The rails will pull out from the coping, the lead bar will bend, and the pulley system will break - essentially every component of the cover. Repair costs for this type of failure is almost as much as a whole new cover. Unless you are made of money, using an automatic cover for the winter is not a good idea.

Pool Closing Kits

In my experience about half of all pool owners buy and use a pool closing kit every year. Does your pool really need one? No, probably not. Does it help? Yes, sometimes. It depends on what is in the kit (or more the quality of what is in the kit) and whether the pool is currently balanced or not.

In order for you to make an informed decision as to if you want to go the extra mile and purchase a pool closing kit you will need to know what is in it, and what it does to the water. While there are many different places to get closing kits and winterization kits, most of them all contain the same selection of chemicals.

Algaecide - Every closing kit comes with an algaecide. This sounds like something that you should add to your pool to prevent it from turning green right? Well, it is sometimes, but not always. There are a lot of different kinds of algaecides. Further to this there are also multiple strengths (concentrations) of each kind. Some algaecides, usually the good ones, have copper in them. This is a subject that could alone be discussed in great length. Some people feel that adding copper to the water is a great idea. It is an excellent algaecide. Other people might argue that adding metals to your water is not a great idea. They can cause staining in the pool and have negative side effects with other chemicals in the water. Copper is also absorbed by the human body through your skin and metal is something that the human body is not good at getting rid of. Lifelong exposure rates to copper, and other metals in the pool water, is a concern worth considering. There is also one more important fact that is worth considering and that is that you already have an algaecide in the water. One of the 4 factors that defines chlorine as the "ideal" sanitizer for pool water is the fact that chlorine itself is an algaecide. It is also an oxidizer and a sanitizer as well as having the ability to hold a residual value in the water being the other 3 defining factors. If your pool is well balanced and chlorinated already then you probably do not need to add an additional algaecide over and above a heavy shock of chlorine before you put the cover on. Discount pool closing kits can sometimes contain lower quality algaecide that does not contain copper...but it also does not contain much in the way of algaecide either. Costco, at least in the area that I am located, sells a very inexpensive pool closing kit every year. These kits come with an enormous jug of low quality algaecide. When (if) you add this to your pool it turns the pool into a foaming mess. Try to avoid poor quality pool closing kits that have algaecide like this that makes the pool foamy.

Stain & Scale Preventer - A pool closing kit usually comes with two liquid treatments. One is the algaecide and the other is usually a stain and scale prevention chemical. The stain and scale chemical is probably the most important, and most valuable additive in the entire closing kit. If you wanted to skip on the kit and just buy a high quality stain and scale prevention treatment then this would probably be worth the few dollars extra. You can get away with no extra algaecide or using your own shock treatment but the stain and scale product is going to benefit your pool in ways that your other chemical treatments can not. The biggest is that the stain and scale product is a metal sequestering agent which will help to remove metals in your pool water which can cause staining. This is even more important if you fill your pool with hard water or from rural water supplies such as a well.

Pool Shock - Pool closing kits all come with some form of pool shock. This is often a stronger granular chlorine product, or if the package is labeled as "chlorine free", then it will contain a strong oxidizer such as potassium monopersulphate. The difference between these two shock treatments is very important. While they both "shock" the pool, their function is the water is different. As previously mentioned, chlorine is both an oxidizer as well as a sanitizer. Granular chlorine primarily acts as a sanitizer, but also as an oxidizer. Non chlorine shock acts only as an oxidizer. So what is the difference? Well, the answer to that is complicated, but for the purpose of closing your pool what you need to know is that both will provide you a "clean slate" chemical state in your pool. A heavy oxidizer dose will eliminate all of the organic debris in the water as well burning off the chloramines (spent chlorine) that is likely in the water. A granular chlorine shock does these things as well, more or less, but also has an additional side effect. Raising the chlorine level in the water will help to protect the pool going into its state of dormancy. Oxidizing is great, and something that you should do to your pool regularly, but going into the winter season I prefer the relative stability of chlorine. Oxidizing is great, and you can almost run your pool completely on oxidizers (not chlorine) except for the fact that oxidizers can not build a residual value in the water. This means that the oxidizer has a short life in the water. You add it, it oxidizes your pool, and that is it. Chlorine on the other hand has the ability to hold a residual. This is a benefit going into the closing season as the chlorine will continue to work long after you have put the cover on. Will the chlorine last all the way to spring? Probably not, but it should be enough to make sure that your water is crystal clear in the spring.

Additional Items - Most closing kits throw in a few extra items to increase their perceived value such as floating chemical dispensers, oil absorbing sponges or an air pillow for above ground pools. None of these items are essential, or particularly even useful, for closing your pool for the year.

What Chemicals Should You Add When You Close A Pool?

So if not a pool closing kit, then what chemicals should you add to your pool when you close it? Actually, not much. By having your pool vacuumed, clean, clear and balanced properly you already are in good shape in terms of your chances to avoid green water over the off season. If you keep your pool well balanced then the only thing that you should add to the water is a strong dose of chlorine shock. Most typically I would add 10L* of liquid chlorine once the pool water level has already been lowered to facilitate winterizing the plumbing. This will give you a strong chlorine concentration in the water, about 7 - 12 ppm free chlorine, which is ideal heading into the winter. As much as 20 ppm free chlorine can be used but this can be hard on the interior surface and potentially bleach the liner or stain the plaster in concrete pools. At ranges close to 10 ppm free chlorine, and with no organic debris in the water, and an isolation cover system, you will almost certainly open your pool to perfectly clean and clear water next year.

*10L of liquid chlorine is suitable for pools 16x32' to 20x40'. If you have a smaller or above ground pool then you should use 5L of chlorine only to prevent staining or damaging of the pool

Tips For How To Keep Pool Water Clear Over The Winter

In addition to the tips listed above there are a few other tips and tricks you can use to make sure your pool does not turn green over the winter. Every pool is a unique situation, for example something like the interior surface condition of the pool will have a large impact on whether a pool will turn green or not. In this example, a rough concrete pool interior surface that is overdue for resurfacing will be much more inclined to hide bacteria and promote algae growth more than a pool with a new, smooth interior finish. The amount of sunlight that beats down on your pool cover, the temperature of the water, the quality of your cover and the length of your off season will all impact your ability to open a pool to crystal clear water. For this reason there is no one solution that will solve every green pool problem. Some of the following tips are specific to certain situations that you may encounter:

Safety Cover Early Startup - If you have a safety cover, either mesh or solid, then technically you do not even need to remove the cover before you start up the pool. Safety covers allow water into the pool over the winter which means that in the spring it is usually full to operating level (if not overflowing). If you have a pool that is full in the spring then you can start up your pool before you remove the cover. The only thing that you would need to do is know where the returns are located so that you can peel back the cover in this location and remove the winterization plugs. Then you can remove the gizmo from the skimmer and start the pool up. You can even add chlorine to the pool with the cover still on. This will allow you to get a head start on cleaning up the water since most safety covers allow silt into the pool. If you have a safety cover that is chronically green in the spring then you can "open" it earlier than normal by leaving the cover on and starting up the filtration system. In warmer temperatures having a cover on the pool during the day can promote algae growth however in the relatively cool spring temperatures you could probably run your pool for up to 2 weeks before taking the cover off, though 48 to 72 hours prior to removing the cover is ideal.

Double Cover Systems - So if you have a tarp system, lock in cover or solid safety cover you have the ability to isolate the pool water which will help to guarantee clear water in the spring. This pretty much leaves mesh safety cover owners with the most difficult challenge keeping the water clear. If you have a mesh safety cover then you can add a tarp under the safety cover to isolate the pool water. The tarp will be held in place by the safety cover and should not require any water bags, or at most, a few water bags to help hold it in place. Using a second cover is an additional step, and is just a little tricky to install both on the pool, but the reward is a guarantee of clean and clear water next season. As an additional benefit, the rugged safety cover keeps all the malicious sticks and objects that could puncture the tarp cover out of the pool. This means that even a cheaper, low quality tarp should last a minimum of a few seasons or more as your secondary cover. In the spring you remove the safety cover and your tarp cover will have water and silt on it but not much in the way of debris to remove. Simply pump off the tarp and open the pool. You can even slip a pump under the safety cover and pump most of the water off of the tarp before you even open the pool.

Adding More Chlorine - If you struggle to keep your pool from turning green in the off season then sometime after you close the pool you can peel back the cover in a few locations and add more chlorine. Algae will only begin to grow in the pool once your supply of free chlorine has been used up. While a cold pool, and one with a cover on it, will use minimal chlorine, it does still use some. Before the freezing temperatures arrive, or first thing in the spring, add more chlorine to help keep the green water at bay. You can use a brush attachment on your skimmer pole under the cover to agitate the water and help the chlorine you add to diffuse better in the pool. Another option to help with keeping your chlorine levels up would be to add one or two large floating chlorine dispensers and fill them with chlorine pucks and leave them under the cover for the winter.

Leaf Nets - If you have a tarp style or lock in style pool cover then you should consider using a leaf net during the closing season. A leaf net can be very useful in keeping the vast majority of debris out of your pool. This will benefit you by protecting the tarp cover and helping to get a long service life from it since most sticks will not ever make it to the tarp. The leaf net also benefits your pool by not letting the leaves sit and rot on top of the tarp for the whole winter. In the spring it will be easier to remove the water from on top of your cover and reduce the chance to accidentally dump dirty water into your pool as you are removing the cover. The biggest problem with pool leaf nets is that most people do not use them correctly. The correct way to use a leaf net on a pool is to stretch it over the pool such that it does not touch the water, using the water bags around the perimeter to hold it tensioned across the pool. Once the leaves have fallen then you are supposed to remove the leaf net. You are not supposed to leave a leaf net on the pool for the winter. If you do this it serves absolutely no purpose other than to be an additional expense and an additional step in the closing and opening process. When used correctly, a leaf new can make cleaning your pool in the spring much easier.

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