How To Drain A Vinyl Liner Pool
It worries me when pool owners start asking questions like "how do you drain a vinyl pool?" because the answer is that you don't drain vinyl pools. In fact, as you can read more about in this article about how to drain a swimming pool, you are not supposed to drain most kinds of swimming pools and doing so to the wrong one, or the wrong way, can have disastrous results. This article in particular is going to look at vinyl pools, both above ground and inground vinyl liners, to help you understand how to drain them...or more accurately to what extent can you drain a vinyl pool safely. Or can you? You had better keep reading and find out.
Vinyl pools require consideration before you drain them. I am unsure how pool owners every came by the idea that it would be okay to go ahead and drain theirs, but in many of these cases draining the pool will result in needing a new vinyl liner. Further to this, draining at the wrong time can even cost you in terms of extra damage to the floors and slopes, all the way up to and including a total failure of your swimming pool which would require an entire rebuild of the structure. Basically a new pool plus the cost of removing the old one, and you had better hope that you still have access in your yard and to the pool area like you did back when the pool was built. If you leave your pool dry and ground water or a heavy rain causes the slopes of your pool to wash out into the deep end, you will probably require some heavy equipment and a good deal of money to resolve this problem.
Never drain a vinyl liner swimming pool. The liner requires manual positioning and a vacuum seal to stay in place when the pool is empty. If you just take away the water the liner moves from the exact position it was placed in during installation and it does not go back when you fill with water again.
So how does this work then? You have seen or have heard of people draining their pools before, or maybe even you have done this for yourself "successfully" in the past. How it works is that when a liner is new it has a lot of elasticity in it. As it ages is loses this stretch ability and will become more stiff and rigid. Past a certain point a vinyl liner has lost so much stretch that it starts to get hard, especially if you let normally wet areas dry out. The end result is that the liner becomes brittle and can actually shatter into sharp pieces, never to hold water again. So when you drain a vinyl liner pool there are a few things that can contribute to how easy, or how hard, the process is going to go for you.
Shape of the floor - If you have a deep end and a shallow end in your pool then you need to be aware that if you remove the weight of the water in the shallow end then the liner will shift because the deep end is still under tension from the weight of the water in the hopper. The floor area of a vinyl liner pool is the single most important part when you start talking about draining your pool. It is absolutely critical that the floor remains covered with water at all times. The exact amount of water that you need to leave would depend on a few different unique factors, and so a general rule of twelve inches of water covering the shallow end floor is the minimum safe amount. Truthfully you can go a little less than this but not too much more before you start to risk shifting, wrinkles and flange tears. If you have a coved floor, which means the floor is deeper than the depth of the bottom of the wall, such that the ground slopes up to meet the wall section, then your safe amount of water would be a few inches above where the cove touches the wall. In addition to the liner shifting and potentially wrinkling, if you leave the floor of a vinyl pool exposed without water covering the liner, you can experience damage to the floor which will require repairs before you can hang a new liner in place.
Age of the liner - A vinyl pool liner is essentially like an elastic band. It has a fair bit of stretch to it, which is more noticeable as the liner gets warm like from direct sunlight or from boiling water being poured on it. However the liner loses that elasticity over time from chemical and UV damage. On average a pool liner will have lost almost all of its stretch after about seven years time. This does not mean the liner is automatically no good anymore, but if you are expecting to drain and then refill and have the liner stretch back into shape, you will be disappointed. The liner stays in place because the weight of the water is immense. But when you drain the pool the liner moves and it will never return as it no longer has the elasticity it did when it was first installed. This is especially noticeable in areas like the corners of your pool where the liner used to fit, but now it is stretched tight as a drum or even popped out from the coping.
How tight the fit is - Vinyl pool liners are custom measured and installed. There is some wiggle room in some of the numbers such that you could have multiple experienced people measure and install a new pool liner, and each liner would be slightly different in shape, and especially depth. Many liner installers attempt to measure the liner such that it will fit in the pool and be slightly smaller than the finished product. When the heat of the summer sun hits the hanging liner it melts like butter into every nook and detail in the wall and floor. The liner will do this whether it is sized exactly right, or way too small. To the end user both just look like a "perfectly fitting liner". However if you jump ahead five or ten years and then drain this pool the liner which was installed with more stretch is more likely to have a problem with tearing or shifting.
In-wall step flanges - One of the largest sources of leaks in vinyl liner pools are flange and gasket systems for in-wall steps. These systems can involve 100 or more screws to be installed in a two part flange. This alone is not the problem, it is the fact that many installers stretch the liner quite a lot to install the steps, especially when installing the steps "dry" versus installing them "wet". This is something that you can read more about in this article about wet versus dry pool step installation. So to start off the liner is already pretty tight in this area in general. Add to this the fact that the vertical area of vinyl on the wall that is above the floor and below the bottom flange is very small. On most vinyl pools this vertical section of vinyl under the flange is only a few inches, up to perhaps a foot maximum. What this means is that if you drain your pool too far, and the liner has shrunk and wants to shift, the area directly below your step flange has very little material with which to provide stretch before the liner will tear out of the bottom of the flange.
Ground water around the pool - If you have active ground water around your pool then draining your liner can be a problem right from the word go. The way that a vinyl liner pool works is that the weight of the water in the pool helps to hold the liner firmly in place against the walls and the floor. If you were to lower the water level in your pool, and you have water in the ground around and under your pool, then your liner will become neutrally buoyant and lift up off the floor and move around. Eventually when the ground water recedes, or you refill your pool, the weight of the water in the pool will press the liner back against the walls and floor...but in a different position than it was in when first installed. This usually causes large unsightly wrinkles that would be difficult or impossible to move once the pool is full of water again. The minimum safe water level in a vinyl pool might be a foot of water in the shallow end, however ground water can make the minimum safe level for some vinyl pools at operating level. Some pools begin to show signs of a floating liner as soon as the water level in the pool drops by a few inches!
Contours like 90 degree corners - As discussed above the liner will lose elasticity every year that it is exposed to water, UV and chemicals. Since the liner was installed with stretch originally, if you remove the water and let the liner shift or pull back to the originally manufactured shape it will not stretch back to the shape of your pool. One of the areas where this is a huge problem is in tight radius corners. Liners are notoriously tough to fit well in tight radius corners, and tight fitting liners with a lot of stretch really give people headaches in the corners. As your liner ages it really does not fit the corner anymore but the weight of the water level in the pool keeps it mostly in place. If you drain your pool too far you are going to have the corners pop out of the coping track and you will not be able to get them back in place.
So how do you drain a vinyl liner pool? Most of the time you don't need to. Many pool owners think that draining is normal for cleaning but it is not. Most of the time vacuuming and chemical corrections can have the pool looking A-1 in a few days at most. The only real times you should drain a vinyl pool is to deal with too much calcium or too much cyanuric acid as these chemicals are removed only by dilution with fresh water. Similarly high total dissolved solid levels periodically require some pools to partially drain and fill, but the important note here is partial drain and fill. Not drain and fill. And yes, sometimes that means you need to partially drain, refill, partially drain, and refill again. Also worth noting that you should leave your pool full if you have ground water, and definitely never lower the water level when you have a lot of rain either recently or forecast in the near future. in a worst case scenario if you drained your pool and found this article looking for answers as to why it looks so bad, you can use a wet dry shop vacuum sleeved behind the liner (or down through the skimmer) to try to suck the air out while you manually position the liner by hand, and with plungers to help you grab it. Use duct tape to help you get a seal around the vacuum hose and any place you can hear air escaping from behind the liner (like along the coping track on some pools). At this point you are essentially installing a pool liner and you might find it helpful to read this article that explains the pool liner installation process.
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