If your pool loses water only when the pump is off, it indicates a suction side leak. This means the leak is related to plumbing components responsible for drawing water into the pool. In such cases, we recommend you check the skimmer, main drain, and any other intake fittings in the plumbing system of the pool.
That said, let’s dive a little deeper and find out more about suction side leaks and other reasons that may cause the pool to lose water.
Pool Losing Water When Pump Is Off: 5 Reasons
Leaks In The Pool Plumbing
When your pool starts losing water, leaks are often the first worry. They’re a pool owner’s worst nightmare because they’re common and tricky to handle.
Leakage starts happening when the plumbing components, such as the pipes, fittings, or joints begin to deteriorate, corrode, or experience physical damage and leave room for water seepage through the damaged areas. These leaks are particularly easier to spot when the pump is off because there’s less water pressure, which makes it easier to find out the place from where the water is escaping.
If you suspect leaks in the pool plumbing, it is always a good idea to start by inspecting the plumbing components, take the necessary steps to spot the leak (discussed in the later section), and fix the problem accordingly.
Cracked Pool Shell
A cracked pool shell is yet another common reason a pool may start losing water. And just like leaks in plumbing, leaks in the pool structure due to damaged or cracked pool lining are pretty common. The shell of a pool may crack due to multiple reasons, including aging, wear and tear, exposure to harsh external factors like pool chemicals, or stress.
When the pool shell develops cracks, the water starts seeping through the openings and eventually, you start noticing a drop in your pool’s water level. Fortunately enough, most cracks are easily repairable with the help of leak sealing products, like the Marlig Fix-A-Leak. But let’s be honest, there will be times when you’ll need to get in touch with a professional and pay the hefty price for pool shell repair because not all cracks are a $20 fix.
Issues in Fittings Or Seals
If the pool’s fittings, such as the skimmer, return jet, lights, or drains are damaged, it can also lead to the pool losing water when pump is off. Pool fittings often have powerful seals to prevent water seepage. However, these seals can degrade over time and allow the water to escape through tiny openings, making the water level in your pool go down as a result.
Evaporation
Sometimes the reason why your pool is losing water is just as simple as evaporation. The amount of water loss that occurs due to evaporation depends on various factors, such as wind, humidity, air temperature, and water temperature.
You might be surprised to know that a pool can lose up to 4 inches of water in a week due to evaporation. This major water loss is the reason why most people mistake it for a leak. But thankfully, there are ways like the famous bucket test, that can help you identify if your pool is losing water due to evaporation.
How To Perform the Bucket Test?
- Put a bucket in the pool, either on a step or any high surface submerged in pool water.
- Fill the bucket with pool water, leaving 2 inches from the top.
- Next, create a reference point by marking the water level inside the bucket and outside for pool water level.
- Turn off the pump and wait for 48 hours.
- Compare the water level inside and outside the bucket after 48 hours. If the pool has lost more water than the bucket, it indicates a potential leak. If the loss of water is equal, it indicates evaporation.
Pool Losing Water When Pump Is Off: How To Fix It
For Leaks
To fix a leak, it is critical to identify the location of the leak first.
- Underground Leaks
Every pool owner dreads underground leaks, particularly because they’re challenging to locate and repair. Here’s how to find if the leak in your pool is underground or not.
- Plug the main drain, skimmer, and pool returns to stop the flow of water into them.
- If the pool water level continues to drop, you might want to look for above ground leaks.
- If the pool stops losing water, it indicates the leakage exists in the underground plumbing.
- Above Ground Leaks
If you suspect a leak in the pool structure or above-ground plumbing components, your next step is to detect the source of the leak. Here’s what you need to do:
- Purchase a leak detection dye kit.
- Turn off the pump, plug the skimmer, main drain, and pool returns, and allow the water to be as still as possible.
- Take the syringe applicator from the pool leak kit and fill it with the dye.
- Now take the applicator at every place you suspect the leak could be and release a small amount of dye at each place one by one.
- Notice if the dye gets sucked into any fitting or pool surface. If it does, it indicates the presence of a leakage in that particular area.
Depending on the nature of the cracks/damages causing the leaks, you’ll either have to use a leak sealant or get in-touch with a professional for repairs.
For Evaporation
Find out if the water loss in your pool is due to evaporation by performing the bucket test explained earlier. If the pool is losing water due to evaporation, consider buying a solar pool cover or try Pool Solar Blanket in A Bottle to stop the loss of water.
How Much Water Loss In A Pool Is Normal?
It is normal for pools to lose water due to backwashing, splashing, or evaporation. In each scenario, the amount of water loss is different, and cannot be particularly quantified in case of backwashing or splashing. The amount of water loss due to evaporation is also highly variable depending on environmental factors. However, pools normally tend to lose a quarter of an inch of water each day and up to 4 inches a week due to evaporation.
Final Word
Suction side leaks are the most common reason for pool losing water when pump is off. If your pool is losing water only when the pump is off, check the plumbing components, such as the skimmer, main drain, and other fittings for leaks. Another possible explanation for the loss of water in your pool are leaks in the pool structure. Whatever the case, you can always stop your pool from losing water by performing necessary troubleshooting steps or getting help from a professional pool service.