All swimming pools lose water to evaporation especially in summer. However, if your pool water is dropping more than usual and you are having to add water all the time you probably need to find and fix a swimming pool leak.
Firstly, you need to measure the rate of decrease of your pool water against the rate of evaporation to determine if your pool really has a leakage problem. If the pool water decreases faster than the normal rate of evaporation you have a leak and you will need to investigate where the pool is losing the water. Adding a dye to the pool can detect leaks in the walls or skimmer box. Test the filtration equipment valves are not leaking water to the drain. Test the plumbing for leaks between the filter and the pool. Once you find the source of the problem you need to fix it before it becomes worse.
Table of Contents
How to Find a Leak in an Inground Pool
How Can I Tell If My Pool is Leaking?
When you need to find and fix a swimming pool leak the first task is to determine if the pool is leaking. You will need to compare the rate of decrease of your pool water against the rate of evaporation to determine if your pool really has a leakage problem. If the pool water drops faster than the normal rate of evaporation you probably have a leak. The way to test this is with the simple bucket method.
The Bucket Method of Finding a Leak
Fill a bucket with pool water to match the level of water on the first step. If you use tap water it won’t contain the pool chemicals, salt and will be at a different starting temperature which may cause a different rate of evaporation.
Place the bucket in the pool on the first step (or maybe the second step is better depending on your pool) and fill with pool water to equal the pool surface. So the waterline inside the bucket is equal to the waterline of the pool outside the bucket. You may need to place a brick or some heavy object under the bucket to make the level right so the bucket is partially submerged with the top part of the bucket is above the waterline.
Mark the waterline on the inside and outside of the bucket with a marker pen or some colored water-proof tape so you can easily see if the waterline has dropped.
Turn off the filtration system pump for 24 hours.
On the next day compare the water level in the bucket to the pool water level. Normally, both levels will have slightly dropped the same amount due to evaporation. When the level in the pool is lower than the level in the bucket then you probably have a pool leak.
If you suspect there is a leak, repeat the test the next day but with the pump operating as normal.
When the amount of water lost is the same as when the pump is off, the leak will probably be in the pool wall, liner or skimmer box.
If the amount of water lost is more when the pump is on then the leak will probably be in the skimmer box and plumbing.
How can I tell where my pool is leaking?
When you need to find and fix a swimming pool leak the second task is to determine where the pool is leaking.
Visual Inspection
When the weather is fine check around the perimeter of your pool for any damp spots or puddles of water forming beside the pool.
If you have an inground pool, do you notice any change in the level of soil, grass, paving or other surface around the pool that would be caused by the ground underneath washing away. This could be caused by a slow water leak.
If you think you have discovered where water is leaking from the pool then you need to fix it.
The Dye Method
Purchase some water soluble dye to use in the pool. Food coloring or the test kit chemicals can also be used.
Turn off the pump and let the pool water settle for at least half an hour.
First put some drops of dye in the skimmer box and watch what happens. Is the dye sucked away into a crack or the return pipe? If yes, there probably is a leak here. It is common for the plastic skimmer box to separate from the concrete walls causing a leak. This can easily be fixed with waterproof silicone sealant.
Next get slowly and carefully get into the water making sure you don’t stir up the water or make any waves.
Use swimming googles or a diving mask to view underwater.
Slowly move around the pool releasing some dye near the wall at varying depths and watch if it is sucked away. If there are any visible cracks, release some dye above the crack and watch if the dye is sucked into the crack.
A common place to get a leak is around a pool light. Release dye by the pool light and check if it disappears behind the light. This leak was easily fixed with waterproof silicone sealant.
You may have to carefully dive down to the bottom releasing dye to check if there are leaks in the bottom of the pool. Try not to disturb the water as the dye will disperse.
One swimming pool had a leak in the tile band around the top of the pool. When the pool was full it would leak down to the bottom tile of the tile band and stop. This leak was easily fixed with waterproof silicone sealant.
How do I find a leak in my pool pump?
When trying to find and fix a swimming pool leak don’t forget to look at your pool equipment.
Firstly, run the pump and make sure there are no leaks from the pump, filter, chlorinator or plumbing.
One of the most common sources of leaks is in the inlet valve that directs pool water to the filter or the drain. Sometimes the valve has not been fully turned to filter and some water is leaking into the drain. Check the valve is correctly set to filter. Maybe the valve is old and leaking water to the drain even when set to filter.
Check when you run the pump that the water is not running into the drain. If your system is old you may need to replace seals or valves. Check the water is flowing strongly through the pump basket (most have a clear lid) and the filter pressure is low. If you have a salt water chlorinator you can see the water racing through the unit.
Professional Pool Repairers
If you cannot find the source of the leak you will need to call in professional pool repairers with specialized leak detection equipment. It will be expensive but you really need to know what’s causing the leak so you can fix it.
They have many techniques such as using cable cameras to check the conditions inside pipes for cracks, blockages or other damage. They can pump compressed air into pipes to check for leaks.
How much water should my pool lose per day?
All swimming pools lose water due to evaporation. It’s normal for a pool to lose 1 to 3 cm of water per week in the summer. If your pool water is dropping more than 1cm per day you may have a leak.
Why does my pool water evaporate so fast?
How much water the pool loses depends on the environmental factors that cause evaporation from a pool.
- Surface area. The larger the pool the larger the surface area and more water will evaporate.
- Exposure to the sun. A pool that is fully exposed to the sun will lose more water than a pool that is partly shaded. A hot sunny day will evaporate more water than a cool cloudy day.
- Temperature. The higher the average daily temperature the more water will evaporate from your pool.
- Wind. If it’s a windy day the evaporation rate will be higher than on a calm day.
- Heating. If you pool water is heated it will evaporate more rapidly than normal.
- Humidity. Low humidity combined with high temperatures means the air is very dry and will cause a higher rate of evaporation from your pool water.
Why does my pool lose water overnight?
Water evaporation still happens at night especially in the summer when the air temperature is warm, there is a breeze or the atmosphere is dry.
Water loss at night can be minimized by using a pool cover when your pool is not being used.
If you only operate your pump at night and the pool is losing water it might be the filtration unit losing water to the waste drain. Check your valve settings to ensure the waste drain is fully closed and all water is passing through the filter on its way back to the pool.
How much water should a pool lose overnight?
Normally a pool doesn’t lose much water overnight because the temperature is lower than in the day but depending on the weather conditions, pool water will still evaporate into the air. The evaporation rate will be lower than the day so the pool water should not drop noticeably at night.
How often should I have to add water to my pool?
During the summer when the evaporation rate is higher and your pool is in constant use you may need to top up every week to keep the water at an optimal level for the skimmer to operate effectively. The water should be three quarters way up the skimmer flap so the skimmer will operate effectively.
If you are frequently backwashing your filter or manually vacuuming the pool to waste you will need to top up the water again.
How to Fix a Leak in an Inground Pool
When you need to find and fix a swimming pool leak the third task is to determine how bad the leak is. Is it only a minor leak and is not getting worse. Or is it losing more and more water each month and you are worried it will turn into a real nightmare?
Pool Lining Leak
If your pool has a vinyl liner and it’s leaking this is easy to repair with a patch kit. Most small repairs can be fixed with water in the pool. Simply place the patch over the damaged area and hold until secure.
Have you found a large tear and it’s deep in the water? You will need to empty the pool to below the damage. This will require a larger patch and lots of adhesive. These patches adhere and dry quickly so you can start filling the pool again the same day.
Pool Light Leak
This leak was easily fixed by going around the light with a waterproof silicone sealant. Sometimes it is better to open the light and using a pool putty behind the light.
Skimmer Box Leak
A common issue with skimmer boxes is that the plastic box separates from the concrete shell causing a leak. This leak is easily fixed with waterproof silicone sealant.
Please read our post on How a Swimming Pool Skimmer Box Works
Pool Pump Equipment
If you found a leak in the pump, filter, chlorinator or plumbing you need to replace the part or repair the connection. Sometimes waterproof silicone sealant will fix it. Other times you may need to replace the housing, connectors, valves, etc.
Crack in Pool Wall
The most common place to find a crack is at the top of the concrete wall behind the tile band. It is less common to find a crack in a concrete pool further down the wall or on the bottom. I have successfully filled tile band cracks with waterproof fillers.
Small cracks in the pool surface of a plaster pool don’t leak. These are usually only cosmetic in appearance.
Larger and deeper cracks will need to be injected with sealant and replastered. Test the crack with dye to ensure it is a leak. Some large cracks will need a concrete wall repair where they brace the wall back together across the crack.
Damaged Underground Pipes
When the underground pipes either bringing water or returning water from the pump are found to be damaged and leaking they need to be replaced.
Usually it is easier to lay new pipes and connect them at each end than to dig up a pipe and repair it. Some pool repairers are able to insert a new slightly smaller pipe inside an old, damaged pipe to effect a repair.
How to Find a Leak in an Above Ground Pool
Finding a leak in an above ground pool is easy. You can usually walk around the pool and detect the ground is wet or sunken due to water running under the pool. You may be able to see where the water is running to.
How to Find & Fix a Leak in an Above Ground Pool
Finding and fixing a leak in an above ground swimming pool is easy.
After you have found the source of the leak it’s easy to apply a patch over the damaged area to contain the leak. You can repair most leaks without draining water from the pool. If there is larger damage such as a tear you may want to drain the pool to below the damaged area to make easier to apply the patch.
- Purchase a vinyl repair kit.
- Cut a piece of vinyl that will cover the damaged area with another 2 inches (5cm) overlap. This will ensure the area is adequately covered.
- Spread the waterproof adhesive over the vinyl patch.
- Enter the pool and apply the patch over the damaged area. You may want to use googles or a divers mask depending on the depth of the repair area. Hold the patch in place until it sticks firmly as per the instructions in the repair kit.
- Check again the next day to make sure everything is ok.
If you vinyl liner has ripped or has multiple leak sites. It’s time to buy a new vinyl liner for your pool.
Conclusion
Discovering how to find and fix a swimming pool leak yourself should not be a daunting task.
It’s normal for all pools to lose water due to evaporation. However, when you find a leak in your pool you need to repair it as soon as possible to prevent it becoming worse. If your pool leak is getting worse it’s costing you water and chemicals. The soil around and under your pool may be wet and eroding away. This may lead to a shift in your pool which could cause further damage to the pool and pipes.