How High to Fill a Pool: A Guide for Beginners

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Summer is finally here, and the best thing about hot summer days is getting to cool down by the pool. But first, you’ll need to fill it up! 

The most common question any new pool owner might ask is: how high to fill the pool?

Generally, you’ll need to fill any pool about halfway up the skimmer box, or you can calculate the needed gallons by measuring your pool’s dimensions.

In this article, we’ve gathered all the information you’ll need to know about your pool’s water level and how to maintain it. So, keep reading!

How High to Fill Your Pool?

Most beginners think that filling the pool to the brim is the way to go. After all, more water equals more pool space! Others might want a shallower pool for their children.

However, that shouldn’t be the case. Maintaining an adequate water level is crucial. Not only will it ensure proper, safe water filtration, but it’ll also keep the pool’s skimmer box from malfunctioning.

There are two ways you can figure out how high to fill your pool, either by detailed calculation or using your eyes. We’ll go through each one of them in detail right below.

Method 1: Calculate Your Pool’s Volume

You’ll simply need to measure the length, width, and depth of your pool. If you have a circular pool, then only the diameter and depth will suffice.

This way, you’ll be able to calculate the volume of your pool, which will let you know the number of gallons of water needed to fill it:

  • Circular pool = 3.14 x radius squared x depth x 7.5 (gallons)
  • Rectangular or square pool = length x width x depth x 7.5 (gallons)

But what if your pool has variable depth? In this case, you’ll need to measure the deepest and shallowest ends of your pool, then calculate the average to substitute it in the formula.

You can also use an online pool volume calculator if math isn’t your strong suit.

Method 2: Check the Skimmer Box

If you need a simpler method that works with any pool shape and size, you can check your skimmer box.

The skimmer box is one of the most important parts of both above-ground and in-ground pools. It uses a weir to capture bugs, leaves and other unwanted debris from the surface of the pool.

The skimmer shouldn’t be fully submerged, but it still needs to be in contact with water. If the water level is below the skimmer you could run the risk of running your pump dry resulting in costly repairs.

Most skimmer boxes have a small arrow along the frame showing where the water level should be.  However, if your skimmer does not have this marking, a good rule of thumb would be to fill your pool about halfway or one-third of the way to the skimmer box.  

Keeping the proper level of water at the skimmer will ensure its effectiveness while protecting the pump.

Differences in Ideal Water Levels for Above-Ground vs. In-Ground Pools

The ideal water level for both above-ground and in-ground pools is still dependent on the skimmer. You’ll still want the water level to be halfway to the skimmer box.

Still, there are some key distinctions between the filling processes of above-ground and in-ground pools.

Above-Ground Pool

It’s imperative to keep water levels high enough in an above-ground pool. 

See, low water levels can cause the liner to shrink. On the other hand, filling the pool to the brim can cause excess water to splash out.

However, it can be tricky to find the ideal water level for an above-ground pool, especially if there isn’t an attached skimmer box.

You can determine the water level by measuring your pool’s dimensions and calculating the area. Ideally, you’ll want to keep the waterline about six inches below the top of the pool.

It can be tempting to fill your above-ground pool at much lower levels, especially if children are going to be swimming in it. 

However, this should be avoided as the pool liner won’t be firm enough without the proper amount of water and could potentially dent from the excess weight.

In-Ground Pool

Unlike above-ground pools, in-ground pools can be harder to fill because of their sheer size.

Due to the larger surface area of in-ground pools, it’s important to keep the water level maintained at the appropriate level to ensure proper filtering through the skimmer.  

Both underfilling and overfilling the pool can each cause their own sets of problems.  While overfilling will prevent the skimmer from properly filtering your pool, underfilling could damage your pump.  

This is why you’ll need to follow the aforementioned guidelines in the previous section to determine the right amount of water needed for in-ground pools.

What Happens If the Pool Water Level Is Too High

It’s a misconception that more water in your pool is better. Sure, it provides extra depth, but it also causes many issues that can be hard to fix.

If the water level is higher than halfway up your skimmer, it simply won’t suck in the water from your pool. This way, your pool won’t be filtered properly.

All the extra dirt and debris will float in your pool, exhausting all the pool sanitizer. Later, the junk will need to be removed through vacuuming or other cleaning methods.  

What Happens If the Pool Water Level Is Too Low

Low water levels can be a real pain. This is a situation all pool owners would never want to face.

Since your pool needs to be regularly filtered through the skimmer, it’s natural for the skimmer to be constantly on. But what happens if there isn’t any water for your skimmer to suck in?

If your skimmer isn’t in contact with water, it’ll still do its job, only this time it’ll draw in air instead of water.

Unfortunately, this puts the filtration system at a high risk of damage. The filtration system is only designed to move water. Otherwise, the pump will eventually overheat and stop working.

Another risk of the water being too low is that your liner could start pulling out of the pool’s track.  This is because the weight of the water keeps the liner held into place.  Once the liner pulls away from the wall it can sometimes be challenging to set it back into position.

How to Maintain Proper Water Levels in a Pool

Now you know how high to fill your pool. You should also learn how to maintain this water level to avoid any damage to the skimmer.

How to Avoid Low Water Levels

Water can be lost from the pool in various ways. First, regular use and active swimming are sure to reduce water levels.

Moreover, the hot weather and sunny days can evaporate a significant amount of water from your pool.

That’s why it’s crucial to check your pool water levels daily, even if it hasn’t been used. Evaporation alone can result in ¼” loss of water each day.  Several hot days can easily cause the water level to go from OK to underfilled.

You don’t need any special equipment. Simply eye the skimmer box for any change in water levels.

Also, if you won’t be using your pool for long periods during the summer, you should cover it. This way, you can prevent any water evaporation and save a lot of time and energy by not having to refill your pool as often.

How to Avoid High Water Levels

In rare instances you may encounter higher water levels. High water level could results from rain or from accidentally allow the hose to fill for longer than intended (oops!).

In the event that your pool is overfilled, you can manually drain water down to the appropriate level.  Alternatively, you could allow the water to go down naturally through evaporation and active swimming.

To prevent rain from overfilling your pool, you can choose to prepare your pool if you know a storm is coming. You shouldn’t be covering your pool in case of a storm since you might risk damaging the pool cover.

How to Properly Fill Your Pool With Water

To properly fill your pool with water, you should take a few precautions to ensure a smooth process:

  • Get a long enough hose, then attach it to an outdoor water spigot
  • Make sure to tie your hose in a way so that it won’t slither out of the pool if you leave it unattended
  • Periodically check the level off the pool to ensure you’re not overfilling it
  • If your fill water is known to have metals, you may need to add a sequestrant to prevent staining of the pool
  • Consider hiring a water delivery service for a faster pool filling process, particularly if trying to fill an empty pool
  • Gather up all the essential chemicals you’ll need to add to your pool to keep your pool water clean and balanced

How Long Does It Take to Fill Up the Pool

Filling the pool can take a LONG time, depending on the size of the pool and the flow rate from your hose.  In most cases, you’ll probably want to go off and do something else other than watch the water level slowly rise –but, at the same time, you don’t want to accidentally overfill it!  

Fortunately, you can easily estimate how long it’ll take you to fill up your pool with a hose:

Step 1 – Determine the flow rate (gpm) of your hose:
Divide 300 by the number of seconds it takes to fill up a 5-gallon bucket with a hose.

Step 2 – Calculate the surface area (sq ft) of your pool based on its shape:

  • Rectangle: Length (ft) x Width (ft)
  • Circle: Radius (ft) x Radius (ft) x 3.14
  • Oval: Short Radius (ft) x Long Radius (ft) x 3.14

Step 3 – Measure how many inches or feet of water needs to be added to reach desired height
Note: If measuring inches, divide it by 12 to obtain the number of feet.

Step 4 – Calculate the number of gallons of water you need to add:
Surface Area (sq ft) x Height of Water to Add (ft) x 7.5.

Step 5 – Divide the number of gallons from step 4 by the flow rate in step 1. 
This provides you with the number of minutes it will take to fill the desired height in the pool.

If you’d rather not run your own calculations, you can use the table below to estimate how long it will take to increase the level of water by an inch.  This assumes a standard flow rate of 12 gallons per minute from your garden hose.

With this information, now you have some freedom when it comes to filling your pool without needing to babysit the process.  

Final Takeaway

Every pool owner should know how high to fill their pool. After all, the proper water level is crucial to keeping the pool water clean and balanced while avoiding any unnecessary issues with the skimmer box.

As a rule of thumb, you should be keeping the water level about halfway up the skimmer box. That way, the skimmer will maintain maximum effectiveness without risking damage to the pump.

If you’re more of a perfectionist, you can calculate how many gallons of water are needed for your pool. Simply, measure the dimensions of the pool and calculate its volume or use an online calculator.

Once you’ve filled your pool to the ideal water level, you can safely enjoy a swim for the rest of the summer!

Happy Swimming!

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