Heavy Hot Tub Cover
Do you have a heavy hot tub cover? Why do hot tub covers get so heavy anyway - and more importantly what can you do to resolve this problem? This problem develops slowly over time and many spa owners do not even notice that their cover is getting heavier and heavier...until it gets to the point that the cover is too heavy to lift that is. Or even worse than this is if you own a hot tub cover lift assist such that you do not feel the full weight of the cover when you remove it to use the spa. In this case a heavy hot tub cover may well go unnoticed until the cover lifter itself breaks under the weight of the cover.
So why do they get so heavy? Quite simply, the cover becomes waterlogged. Hot tub covers are made from foam which is wrapped in a vinyl covering. When they are new (and dry) even a large cover can be light enough to lift with one hand...but after many years of use they will begin to take on water. When this happens there are a few different factors at play:
Open Cell VS. Closed Cell Foam - There are a few different kinds of foam that can be used inside of a hot tub cover. Most of the time you will have white polystyrene foam sheets however some (more expensive) covers use an injectable foam similar to expanding foam that you might buy in a hardware store for filling gaps around windows and doors. Closed cell foam means that the foam has been manufactured in such a way that it is effectively "sealed off" on all sides. Open cell foam means that the cellular structure of the foam is such that water can (and will) wick into the foam slowly over time. If you were to submerge closed cell foam into water it would resist absorbing any water regardless of how long it is submerged. Open cell foam will begin to absorb water immediately upon immersion.
Why Do Hot Tub Covers Absorb Water?
So is it to say that polystyrene will always absorb water and injectable foam will not absorb water? Well yes, but at the same time, no. Let me explain. First you must realize that a hot tub cover lives in a very harsh environment. It is exposed to constant water and moisture as well as extreme temperature differentials. Hot tub cover manufacturers know this and try to build covers to withstand these elements. How do they do this? They wrap the foam in something to prevent water from permeating the foam. In most cases this would be a sheet of poly plastic wrapped around the foam before it is placed into the vinyl cover. The purpose of this plastic is to (try to) prevent water from being able to reach the foam...and to a certain degree it does work. More accurately is works for a period of time. Unfortunately plastic is not waterproof. Wrapping the foam in plastic will not prevent water from absorbing into the foam...but it will definitely slow it down.
Polystyrene (white styrofoam) is actually closed cell when it is manufactured. It is when the foam is cut into the shape for the cover that the cellular structure is opened. Most (cheap) hot tub covers are a single piece of foam which is cut in half in the center to make up the two sides of the cover. It is the act of cutting this foam which opens the cellular structure and begins the slow and steady progression towards a waterlogged and saturated cover. Plastic slows down the process, but five to seven years is usually enough time for water to find its way in through these cut edges and compromise the cover. So what if you have a cover that got too heavy long before this amount of time? This would almost certainly be from damage somewhere in the cover (and protective plastic) which is allowing water to directly access the foam. If you ever notice a cut or slice in your hot tub cover that goes through the vinyl and the plastic you must fix this right away or it will eventually cause the early failure of your cover.
How To Stop A Hot Tub Cover From Getting Waterlogged?
There are a few different things you can do to get the longest life possible out of your hot tub cover. First, as mentioned in the above paragraph, if your cover has a rip, tear or slice in it you must fix this immediately. Other than this there is actually very little that you can do to make your cover last longer other than to buy a higher quality cover to begin with. Have you ever wondered why two covers which are the same thickness can vary so much in price? This is due to more expensive covers taking more steps to help prevent the absorption of water.
Mylovac VS. Plastic - Cheaper hot tub covers are simply wrapped in plastic to slow down the rate of water absorption. More expensive covers use a more comprehensive approach as well as more expensive materials to mitigate this problem. Mylovac is a metal-like product that has far greater resistance to water permeability than plastic. You are probably familiar with mylovac as the product that bags of chips come in...and it is completely waterproof. Higher quality hot tub covers use mylovac to wrap the foam in to help stop the absorption of water. Unlike plastic wrapped foam which will eventually take on water, mylovac wrapped foam will not unless the mylovac wrapping becomes cut or damaged in some way. If you want to buy a hot tub cover that will last as long as possible, then you need to seek out a cover that uses something other than plastic to create a waterproof barrier.
Preventing Damage To Hot Tub Covers - As stated above in this article, polystyrene is closed cell unless it is cut, but once you cut into it you open the cellular structure and provide a pathway of entry for water and condensation to wick into the foam. Many hot tub owners abuse the covers by putting them on the ground when the spa is in use which can increase the potential for damage to happen. Another big killer of hot tub covers comes from people (usually kids) climbing and jumping on the cover. This can result in cracking the foam, which similar to cutting, opens the cellular structure of the product. Any deficiency in the foam, cuts in the foam, or cuts in the protective plastic or mylovac layer, will result in advanced water absorption.
When you buy a hot tub cover you should inquire about the construction methods used. Most specifically I would want to know if the cover is made from polystyrene or expandable foam. The vast majority of spa covers are made from polystyrene which would then lead you to ask the question whether the foam is cut in the center or manufactured as "left side" and "right side". It might not be straight forward to get these answers even if you are asking the right questions unfortunately since how would you be able to tell the difference from one to the next? The answer to this is simple...price. Finally you would want to ask about what material is used to wrap the foam in. Most covers will be plastic, in which case you should ask about the thickness (in mil) of the plastic sheeting used. By asking these questions you can begin to build a technical profile of how well (or not well) the cover has been manufactured. This allows you to compare spa covers on something more than just the price.
How To Fix A Heavy Spa Cover?
This is a question that comes up all the time...so you have a heavy and waterlogged hot tub cover and you want to know how to fix it. Unfortunately the only fix is to replace the cover. While it is possible (in theory) to order replace foam inserts, the amount of money that this saves you is very small, if anything, over the cost of a brand new cover. A sagging hot tub cover is sagging under the weight of the water it has absorbed. This is a structural failure of the product which can not be fixed. Even if you were to do something like re-support the cover with wood or something else, it is important to understand that once insulation gets wet it loses all of its insulating abilities. This is why if you have a leak in your roof and your insulation gets wet you will need to replace it.
I have read many resources online with ideas about how to remove the water from hot tub covers ranging from sitting it out in the sun, to sealing up your entire cover into a gigantic bag of kitty litter to absorb the water. The logic of these methods is simply flawed. Once the foam has absorbed water you will never be able to get the water out. As a real world example, I own a business that makes statues. These statues are made from foam which is wrapped in steel and then modified concrete applied overtop. Do you know where I get all of the foam to build these statues? You guessed it...old hot tub covers. Instead of spa owners paying to dispose of old covers I pick them up for free and recycle them into statues.
In the process of growing this statue making company I have picked up, stored, and used somewhere around 500 old hot tub covers. Many of these covers are stored in my shop area for years, with some of the oldest ones being over 10 years old before I get around to using them. I strip the vinyl and steel out of these covers and stack them such that they have airflow. Even after ten years of sitting in dry storage these covers are still heavy...some of them as much as 100lbs or more. I fail to see how it can take a spa cover years to absorb water, but sitting it in the sun for a few days is supposed to resolve this problem. Save yourself the headache with waterlogged covers and get rid of it. Either by replacing the foam, or the entire cover. Once styrofoam absorbs water it does not let it go. I have even gone so far as to chop up covers into small cubes and bake them in the sun for weeks on end to no avail. Once a hot tub cover absorbs water the only viable solution is to replace the saturated foam.
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