How to Fix a Sagging Hot Tub Cover

A sagging hot tub cover can be a bit of a problem as it will mean that you get pools of water standing on top of your hot tub. These will eventually discolour the cover and also, the added weight of the water will potentially make the sagging hot tub cover even worse. If your hot tub cover is sagging it could, unfortunately, indicate a more serious issue with your cover but equally, there is a chance that you will be able to fix it quickly and easily for free as well!

So, how do you fix a sagging hot tub cover? Remove the hot tub cover from the hot tub and unzip the zips. Lift out the foam core from inside the cover and inspect it. If the plastic vapour barrier surrounding it is intact and the foam core doesn’t seem waterlogged turn the foam core over/swap it around with the other side and put it back in the cover. If the core is damaged or waterlogged it will need replacing. Check to see if the rest of the hot tub cover is serviceable or whether the whole cover needs replacing.

Why do I have a sagging hot tub cover?

The inside of your hot tub cover is made from a styrofoam core. Styrofoam is a fantastic insulator and, in fact, if you have a look at this chart here you will see that it is one of the very best insulators and even better than wool felt or rock wool. However, it’s not particularly strong as it’s main feature is that it is full of tiny air pockets that provide such effective insulation.

This does mean that styrofoam is generally very light though which is why it is good for hot tub covers as, to cover a whole hot tub, the hot tub cover needs to have two or more very large sheets of styrofoam. The problem is that the foam isn’t that great at supporting it’s own weight. If you regularly put things on top of your hot tub cover or the cover gets weighed down with snow, for example, it will put a strain on the foam core and it will sag.

However, the biggest problem that causes hot tub covers to sag is when the foam core becomes waterlogged. All of the tiny insulating ait pockets become full of water and extremely heavy. This then causes the cover to sag as gravity does it’s pulling down thing!

What can stop a hot tub cover from sagging? 

Obviously hot tub cover manufacturers are fully aware of the potential problems with sagging hot tub covers and so they add reinforcement to the covers in terms of internal bracing. Usually, this is enough to stop the foam from sagging but not always.

You will also probably notice that most hot tub covers have a convex or raised centre portion to them. This allows rainwater to drain off the cover and also helps provide some additional strength as well. It is also usually the case that the more dense and thicker the hot tub cover is the better insulator it will be and also the stronger it will be as well. Naturally, the stronger, thicker and more thermally efficient hot tub covers are more expensive too!

How to fix a sagging hot tub cover step by step

Remove the hot tub cover from the hot tub –  The first job is to remove the cover from the hot tub.  You need to remove it completely and get it onto the ground to make the job easier.  This is probably best done with two people particularly if your hot tub cover has got a bit waterlogged and has started to feel quite heavy.  If you have a hot tub cover lifter this will make the job much easier but otherwise, you need one person on each side of the hot tub cover to lift it off safely onto the ground.  If you do have a willing helper then ask them to stick around because once you have unzipped the hot tub cover you will need to remove the foam cores and this is actually an easier job with two people.

Unzip the sides of the hot tub cover –  With the hot tub cover on the ground unzip both sides.  If you have a relatively new cover then you shouldn’t have any problems doing this but if your cover has been on your hot tub for quite a while and you haven’t moved the zips then you might find this a little bit more problematic.  The hot tub cover gets bombarded with all sorts of moisture and chemical vapours and so often the metal parts of the cover are attacked and can start corroding. 

If the zipper is fast and is corroded the most important thing is that you don’t try to open it by using brute force.  The chances are that if you do this you will break the zipper or possibly tear the vinyl of the hot tub cover which is likely to be a difficult and possibly expensive repair.  You can try scrubbing the zipper with an old toothbrush and water, or if you can get it open some of the way, using beeswax on it, or you can try using baking soda or a special zipper lubricant.  There are some fantastic ideas in this post to help.

Remove the foam cores from each side – Once you have got the zipper fully undone you can now remove the foam cores from inside. They are likely to be a very tight fit and you probably won’t be able to just lift them out of the cover.  If you still have your willing helper then if one of you holds onto the vinyl cover and the other one pulls on the inner foam core you will probably find this the easiest way.  Pull each foam core out carefully jiggling it around a bit at a time so that you don’t put an excessive amount of strain on the vinyl cover and risk damaging or tearing it.

The other thing to be careful of it is to make sure that you don’t tear the vapour barrier around the foam core.  If you do damage the vapour barrier it could potentially allow moisture to get into the core and for the core to become waterlogged.  However, if you do, it is relatively easily fixed with strong gaffer tape or by putting a waterproof patch over it.

Remember also that the foam cores are relatively brittle and aren’t designed really to take any lateral movement.  If they do get an excessive strain on them they could potentially crack, particularly if they are sagging rather badly already, so do take your time and extract the foam cores as carefully as possible from the vinyl covering. 

Inspect the foam cores – With both foam cores now out of the vinyl covering it’s time to have a good look at them.  If the vapour barrier is damaged and you can tell that the core is full of water then you will need to either dry the core out or to purchase a new one.  If the vapour barrier is really badly damaged in lots of areas then it may not be a particularly easy job to repair it and then a new foam core might be the best solution as well.  Check to see if either of the cores are cracked or seriously damaged or are they just sagging under their own weight?

New foam cores are readily available either online or from your hot tub supplier and are relatively inexpensive and easy to fit. However, it is false economy to fit new foam cores into a damaged vinyl cover.

Dry out the foam core –  Hopefully, your core will be dry and won’t need any further attention but, if you can see that your foam core is waterlogged, then it might well be worth having a go at drying it out.  Bear in mind though that once a core has started taking on moisture it’s very difficult to get all of the moisture out of it and it will soak up moisture again more quickly than a new core.  However, it can be worth having a go at drying it out as a temporary measure to save some money in the short term.

Drying the core is very simple and you just need to put it out in the sunshine possibly for a number of days to allow the water to evaporate.  It’s a good idea to stand the core on either some planks of wood or on some bricks as this will allow the air to circulate around and allow for more even drying.  You will probably find that the water will recede downwards as well so if you turn the core over and regularly it will dry a little more evenly too.  This whole process could take several days, and even after this time, you might still have some moisture locked inside the core. 

The core will dry much more easily if you remove the vapour barrier first.  Even if the vapour barrier is seriously damaged it will still lock in some moisture so take the whole vapour barrier completely off the foam before trying to dry it out.

Repair the vapour barrier –  If you need to do a repair to your vapour barrier, or you need to replace your vapour barrier it’s simply a case of adding a waterproof plastic covering over the whole of the foam core.  The main problem with this is that if you add too much extra plastic covering you will find that the foam core will fit too tightly into the vinyl cover and you might have a job getting it could go back in.  Try to keep the new plastic as tightly wrapped around the foam core as possible and repair any small holes with waterproof tape.

Inspect the hot tub cover vinyl –  Whilst you have got the hot tub cover apart it’s a good time to have a look at the vinyl cover itself.  If the core isn’t waterlogged and is dry then the vinyl is probably in good condition. However, if you do have a water problem inside of the core then you do need to look at the vinyl very carefully as there is most likely a ripped area or weak spot which is allowing moisture in.  This might be repairable or it might just be time to bite the bullet and get a new hot tub cover.

Replace the foam cores –  If your foam cores are dry, or you have spent some time drying them out then it’s time to put them back into the vinyl cover.  The key here is to put them in the other way round so that they go in with the sagging bit upwards rather than downwards. Over time they may well sag back down again but for the moment this will solve the problem and you will be left with a nice convex hot tub cover which will allow the water to run off. 

Take your time putting the foam cores back in again. You will probably need a helper to help you do this.  Be very careful not to damage the vapour barrier on the cores and also not to strain the vinyl cover in any way to avoid damaging it.

Replace the hot tub cover –  Once the cores are back into the cover and have been swapped over then zip it back up again.  It may well be worth giving the zipper a light smearing of beeswax to help keep it in good condition in case you need to open it again in the future.  Get a helper to help you to lift the hot tub cover back onto the hot tub safely.

How can I prevent my hot tub cover from sagging?

Buy a good quality hot tub cover –  Good quality hot tub covers will not only be much more thermally efficient but will also be stronger as well.  They will have much better bracing inside and so the chances are that a good hot tub cover will not sag as easily.  A good quality cover will also save you a lot of money in energy cost and it will be much better at keeping the heat in your hot tub.

Don’t put things on top of your hot tub –  Hot tub covers are not designed to take any extra weight other than themselves.  Do not be tempted to store things on top of your hot tub cover and also discourage children from climbing on top of it as well.  If you have heavy snowfall it’s also a good idea to scrape it off from the top of your cover too.

Take your hot tub cover off regularly –  You should try to take your hot tub cover off on a weekly basis and leave it out on a sunny day for a while to dry.  This regular drying will greatly increase the lifespan of your hot tub cover and also decrease the chances of it becoming waterlogged and sagging.

Use a hot tub cover lifter –  Using a hot tub cover lifter makes it much easier to manoeuvre a heavy hot tub lid around.  If you are tempted to lift a hot tub cover off just by yourself you may put excessive strain on one corners of the cover as you lift it.  This excessive strain can, over time, be the cause of sagging and misshapen covers. If you do not have a hot tub cover lifter then try to use another person to help you lift a hot tub cover off so that you can have one of you on each corner to even out the strain. 

Related Questions:

Why is my hot tub cover so heavy? – If your hot tub cover had become very heavy then it means that the foam core inside has become saturated with water.  The chances are that the vinyl cover is damaged and is letting in moisture and also the Vapour barrier that surrounds the core is damaged as well. If your hot tub cover is heavy and full of water it will be much less thermally efficient and will be costing you more energy to keep your hot tub warm. 

When is it time for a new hot tub cover? If you know that your hot tub core is waterlogged then the chances are that the vinyl cover is damaged. If the damage is extensive then it may be beyond repair. Often the vinyl becomes cracked with age, exposure to UV light and also die to chemical attack. Hot tub covers generally last only a few years so, over the life time of your hot tub you would expect to have to replace your cover a few times.

If you are looking for a new hot tub cover then have a look at my really helpful post here!

Can I replace the foam in my hot tub cover? Yes, you can just replace the foam cores of your hot tub cover. It is false economy to replace the cores if the outer vinyl is leaking water though so check this first. If you do want to replace your cores it is relatively inexpensive and easy to do.