While the pool provides endless fun in the summer heat, there are many regions where it’s just too cold to keep the pool open in the winter. Freezing temperatures can cause catastrophic damage to a pool that hasn’t been properly winterized.
One of the key steps during the closing process is to place a cover onto the pool. The cover will help protect the pool throughout the off-season.
There are two primary types of pool covers: solid covers and mesh covers. Both covers are intended to protect the pool from debris and reduce UV rays that could promote algae growth.
The primary difference in the two covers is in their design. The mesh cover allows rain and melted snow to pass into the pool, while the tarp-like solid covers typically prevent the entry of water into the pool.
However, many pool owners that use a tarp cover have been met with a surprise when opening in the pool in the spring –the water is lower than when they closed the pool! Sometimes it could be several or more inches of water that has seemingly disappeared.
While the first thought to this befuddling surprise may cause suspicion of a leak, this fortunately is not always the case. The next question that typically rises is “Does water seep through the pool cover”?
In short, yes, water can seep through pool covers. But, you may be surprised to know that is not the only reason why your pool may lose water over the winter.
We’ll explore how water can seep through a pool cover, and the potential issues it can cause. Let’s jump in!
How Does Water Seep Through Pool Covers?
Mesh covers are great at keeping debris out, while allowing natural precipitation into the pool. These covers are generally taut across the pool’s rim –well above the water’s surface– in which you don’t have to worry about water seeping out of the cover from the pool aside from minor evaporation.
Conversely, a solid tarp-like cover made of PVC or vinyl is generally intended to be waterproof. It’s why you sometimes see tarps laid over a leaky roof –they will keep the water out.
When applying a solid cover to the pool, it’s recommended that the cover lay atop the surface of the water. As rain or snow accumulates, the underlying pool water will help hold the weight to prevent the cover from collapsing.
Water bags or other weights are laid along the perimeter of the cover on the pool deck to keep it in place.
Over the course of months, it’s likely that a significant pooling of water will accumulate on top of the cover. This could be caused by natural precipitation, or it could actually be pool water migrating through a hole in the cover. By springtime, it may actually look like a large pond across the top of the cover!
Small holes in the cover may cause some water to seep through from the pool on top of the cover. Larger tears in the cover could allow for an even greater amount of water to escape the pool.
Holes in the cover could also allow for mucky water that sits on top of the cover to fall into the pool. This could increase the chance of opening the pool to green water.
When opening the pool in the spring, you’ll need to clear the water from the top of the cover, oftentimes with a small pump or siphon. It’s possible that some of this water being removed is actually water that has seeped through the cover.
To help prevent this, inspect the pool cover before placing it onto the pool. If you notice any holes or tears, you may be able to patch it with a tarp repair kit or even simple duct tape.
While holes in the cover could cause some water to seep out, there may be another reason why the level in the pool is lower in the spring: water displacement.
Water displacement is more common for above-ground pools, but in-ground pools can experience this as well.
This displacement can occur when the weight of snow and ice on top of a cover forces the underlying pool water to seep onto the pool deck. As water turns into ice, the ice expands and causes water to be displaced from the pool.
Ultimately, when the cover gets removed in the spring, it can become quite evident that a large amount of water has left the pool.
To help limit the amount of water displacement during the winter, you can try to clear as much snow and water off the pool cover. This may be easier for above-ground pools than in-ground pools.
For in-ground pool owners, if you suspect that the pool water has been displaced, you’ll want to take care not to pump water off the cover too far in advance of actually removing the cover. The water on the cover actually provides the benefit of keeping pressure against the liner to hold it in place; removing the water could increase the risk of the liner pulling from the wall.
Once the ice has melted, you can slip the hose under the cover and start filling the pool. This will help keep water pressure on the walls of the pool as you remove water from the cover.
The more water drained from the pool prior to placing the cover will reduce the amount of water that is displaced during the winter. However, you’ll still need to add the water back in once the cover comes off in the spring!
While displacement is common, you’ll want to also keep an eye on the water level in the pool to rule out a potential leak after it’s been refilled.
Too Much Water on the Pool Cover
Especially for above-ground pools, having too much water on the pool cover can wreak havoc. The water may eventually freeze into a solid block of ice.
This heavy block of ice can displace water from the pool causing the cover to sag deeper into the pool. Without water supporting the underside of the cover, the weight of the ice could actually pull in the walls of the pool causing irreparable damage.
To quantify just how much weight we’re talking about –each inch of water on a 24’ above-ground pool weighs about 1 ton! A couple of rain or snowstorms can easily transform into several tons if the collected precipitation is not periodically removed from the cover.
Aside from the risk of structural damage, the pool cover is also more at risk of developing thin spots or holes when a large amount of water is on the cover. This could eventually allow for water to seep through the cover.
How to Keep Water Off the Pool Cover
It may sound easier said than done to keep water off the pool cover. Afterall, we don’t control the weather!
Fortunately, there are a few simple solutions:
1 – Pool Cover Pumps
A submersible pump can be placed onto the cover and will remove water from the surface. The easiest solution is an automatic pool cover pump, which will remove water automatically as it begins to accumulate on the cover.
If you live in a freezing climate, you may need to remove the pump before the bitter cold arrives.
2 – Pool Pillows
Pool pillows provide a cushioned mound underneath the cover. The hill formed by the pillow will help prevent water from collecting in the middle of the cover.
Alternatively, several large inflated beach balls can also be used in place of a pool pillow.
3 – Hose Siphon
A cheap, but trusty solution is to use a siphon method. This requires a bit more manual effort than the other options, as you’ll need to start the siphon by running water through the hose initially.
Once the siphon is started though, gravity keeps it going until the cover runs dry.
How Much Water to Put on Pool Cover
While we’ve looked at why it’s important to prevent too much water from collecting on the pool cover, there is actually some benefit in having some water on the cover.
A couple inches of water on the cover can help keep the wind from whipping it around. This amount of water is unlikely to cause a significant amount of displacement of water from underneath the cover.
If you’re using a solid cover that is sold by a pool supplier (rather than just a large tarp), the manufacturer may also have recommendations as to just how much water should be placed onto the cover.
Does water seep through a pool cover? Yes, it’s totally possible for water to migrate across a pool cover.
The amount of water that seeps through depends on the type of cover, the condition of the cover, and the amount of water that is on the cover. Using a cover pump or siphon are simple tools that can help keep too much water from accumulating.
If you’ve found that a lot of water has been lost after opening the pool in the spring, don’t automatically assume it’s a leak! It very well could be caused due to water displacement that occurred throughout the winter.
Happy Pool Upkeep!
Husband and father of three (actually, four if you include the pool). I’m an avid DIY-er and weekend warrior that enjoys taking up new projects around the house to help us maximize leisure right at home. I enjoy researching and sharing various tips, tricks and knowledge to help others make their home an oasis.