My Pool is Losing Water!

Much like a leaky hot tub, having a pool that seems to be mysteriously losing water can be a serious problem. We hope we can help you troubleshoot your water loss woes and help you find the source of the issue so that it can be resolved quickly and efficiently. Pools can be a valuable resource and aren’t necessarily wasteful. That can all go out the window if your pool is losing water.

Note: If you do notice a leak, DO NOT immediately drain your pool. It’s important to have water in it in order to locate the source of the water loss.

How often should I have to add water to my pool under normal conditions?

You should know that your pool will lose some water through a number of normal means: splash-out during use, backwash waste, and evaporation. Depending on the climate where you live, you may gain some of that back via rainwater. However, if you find yourself adding more than two inches of water to your pool per week, there’s a chance you have a major leak somewhere in the pool. Rather than just constantly refilling the water and ignoring the loss, spend some time and money to repair it as soon as you notice it happening. Otherwise, you can find yourself with a much larger problem (and bill) on your hands.

Why do pools leak?

Pools are constructed so that they are watertight and even though pools seem pretty basic, there are a lot of parts and pieces involved in keeping it that way. Seals deteriorate, pools may shift over time, or the ground it’s dug into settles. Pools often leak through plumbing fittings, accessories like light fixtures, and even through the shell or liner. It’s critical to find and fix leaks to not only save monetarily on things like water, heat, and chemicals, but to keep from the undermining pool structure from gaining water and washing away fill dirt.

How do I find out if I have a leak?

Leak detection is complicated and can be time consuming. In some cases, it may require a professional, both to locate and to repair. However, you can rest assured that most pool leaks are caused by something minor and are relatively inexpensive. If you troubleshoot through some of these common scenarios, you could save yourself money by either stopping the leak or being able to tell your local pool professional exactly where the problem lies.

Check the evaporation rate

You can see how much water your pool is losing by filling a 5 gallon bucket with water and placing it next to the pool so they are in the same conditions. It doesn’t necessarily have to be full, but should be filled enough so that you can measure if there is some loss. Mark both the water line of the bucket and the pool. After waiting 24 hours, check the water loss on both the bucket and the pool itself. If you notice that the pool has lost more bucket than your control group (the bucket), then you most likely have a leak. If you’re not sure whether or not your pool needs more than 2 inches of replenished water weekly, it’s a good way to double check. Using a solar cover or liquid solar cover can help prevent evaporation.

Here are some other things to check before calling a service person for repairs:

Is the pool leaking with the equipment running or when it’s turned off?

This is a good place to start. If you turn off all of your pool equipment like the pumps and filters and you’re still leaking water, this could indicate that you have a pressure-side return leak. When the filter pump runs, the plumbing on the pressure side is under pressure. This can turn what would start as small drips into significant amount of spray that can make your pool lose water rapidly. Check the waste or backwash line to see if the water is consistently running.

If the pool is leaking without your equipment running, you could have a suction-side leak. With the filter pump ON, the plumbing on the suction side is utilizing a vacuum action. Air is often drawn in through leaking voids which keeps the pool from leaking. If you look in your pump basket, you may see a lot of air through the lid. You may also see air bubbling OUT of return lines or air building up in the filter tank. A quick fix in this situation would be making sure your pump basket lid is secured with a lubed O-ring that isn’t cracked or rotting.

What if my pool leaks all the time?

If your pool has leaks regardless of whether or not the equipment is running, it’s likely that the shell, plaster, or vinyl has a crack where the water is escaping. If you think you’ve found a crack but aren’t quite sure if that’s the origin, place some pH indicator test reagent near it with the pump shut off in the still water. If the dye is sucked into the crack, you’ve found your leak. This also happens a lot near underwater lights, especially the in the conduit where the light runs to the junction box. You can remedy this by filling the opening of the conduit in the back of the socket with a putty or other caulking agent appropriate for your pool construction material.

It could also be happening inside the skimmers. The most common origin for leaks is when you have a separation between the plastic skimmer and the pool (most often in concrete shells). This can be fixed with a bit of pool putty or a little Mr. Stick Underwater Glue.

My water leaks to a certain level and then stops. What’s going on?

If you are losing water and then it seems to level off at some point, this can help you determine where the leak is originating. For example, if you close the skimmer valve and the water drops below the skimmer and keeps going, it’s probably not the skimmer. If your water dips below an underwater light and then stops leaking, that’s a good indication of where you’re losing the water.

If your water stabilizes at a certain point, try using the dye test in areas around this level. Look around for small debris or movement around a certain area—this is a good indicator where a crack or void may be sucking water.

If your water level dips to the bottom of the skimmer and stops, you most likely have a suction line leak, most likely directly under the skimmer. If the pool water level goes down to the bottom of the return jets and stops, this means you have a return line leak, most likely directly by the wall jet return fitting although it could be anywhere in the return line.

Do you see any wetness accumulating outside of the pool?

If you have noticed water leaking around the pool and creating puddles or wet soil—especially between the pool and the equipment pad—you’ll want to have someone address it immediately. This can lead to erosion and a whole slew of far reaching issues. If you think the leak is originating at the equipment pad itself, take a look at the filter, pump, heater, and all the valves to see if you can spot any spray or abnormal water accumulation. Turn the pump on and off and look for changes in water spray with each change. This should help you find an origin.

Is your pool vinyl?

Vinyl pools are the most likely to get tears and have leaks. Since the material is thin, it is far more susceptible to rips and tears than your standard plaster or concrete pool. Vinyl pools usually have leaks around the fittings like the skimmer, returns, or the cleaner line. You can also look for sinkholes underwater where it looks as though the fill sand under the liner may have washed away due to a leak. Steps, corners, and where the ladder attaches to the wall are another common place for leaks to occur. You can repair vinyl linings yourself with vinyl patches, but the whole lining generally needs replacing every decade or so. Keep in mind that you may have more than one leak, too.

How much does leak repair cost?

Because pool leaks can be hard to find and difficult to assess, they may require a service person to come out more than once. I would say the average range is anywhere from $150-$250 for the standard leak repair. It can obviously be much more if you have a serious issue that requires concrete cutting. Just remember, it’s better to find it as soon as possible and try to fix it before it gets out of hand and costs you some serious money. Never ignore the problem! Hopefully some of this troubleshooting will help save you time and money as you’re able to locate and even fix the issue yourself when you notice your pool is losing water.

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Gregory Hakanson
February 24, 2021

I did the bucket test and the evaporation checked out normal about 1/4 of an inch 24/48 hrs.. I then turned on the pump, I have no leaks on the suction side around the valves and, no bubbles at the pump, but my pool seems to be loosing water. I checked around the pool and see no signs of wet soil. What next!???????

February 24, 2021

My pool leaked at the elbow attached to the botton of the weir many years. This was caused by sand etc wearing away the onside of the PVC elbow. The water has again dropped to the bottom of the weir. Tomorrow i will probably find no water in the filter basket at the weir. Then it entails taking up at least 8 bricks and digging down to the elbow. Hope the stainless steel clamp has a stainless steel bolt.

Andrea Mosley
April 26, 2018

Our pool loses water when the pump is running which includes the attached Jacuzzi. Where do we start to find out why?

Heidi lotthammer
October 16, 2016

A friend of mine dried to put a part into the skimmer from my barracuda,but another peace was still stuck so he had to get the part out first ,now my pool leaks water up to the skimmer and i cant turn it on,
Any suggestion,i am on a fixed tight budget,thank you

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