Why is my pool water disappearing?

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Why is my pool water disappearing?
Is your pool losing water? You might be surprised to know how often pool owners incorrectly assume that their pool is losing water. It might be...pool leaks are common unfortunately and can be elusive to find, but before you can even ask yourself why your pool is losing water you should be doing some water loss tests to confirm that the pool is, in fact, leaking. There are a number of factors that can contribute to water loss in the pool so the first part of fixing your water loss problem is to rule out them out.

Splash Out - Just how much water do you lose in a weekend full of cannonballs and half-crazed children splashing about in the pool? How can you be certain that the pool is losing water if you are losing an unknown amount to splash out? You could close the pool off to swimmers for a few days while you test the rate of water loss in the pool, or you can mark the water level before the pool gets used by the kids. When they are done for the day you can check how much water was lost during a day of playing in the pool.

Filter Maintenance - Do you have a filter that requires backwashing maintenance? Backwashing of a pool filter uses enough water to note a drop in the water level of the pool in just a few minutes. Do you backwash the filter yourself or do you have a maintenance company that does this for you? Are you perhaps mistaking water loss in the pool for explainable backwashing of the filter?

Evaporation - Evaporation is one of the worst offending factors for tricking pool owners into thinking that their pool is leaking. Rates of evaporation change in swimming pools depending on water temperature, ambient air temperature, wind speed, and humidity. These factors all change over the course of a swimming season and it might be that the rate of water loss in your pool is explainable as evaporation. If you use a solar blanket or a safety cover on your pool then this will dramatically lessen the rate of water evaporating from the pool. Did you recently stop using your solar blanket? Pool owners often start the season strong with diligent use of the solar blanket, which can limit evaporation, but later in the season it becomes tedious to put the blanket back on, it gets skipped, which would increase your rate of evaporation.

Leaking Water - The final way that water gets out of your pool is that it is escaping the system somewhere. Swimming pools are designed to be leak free however most swimming pools leak at least a little bit. Understanding that it is not all that uncommon for pools to leak is important. If you have an area of your pool that does not look quite right for whatever reason, and you have suspected it might be leaking in this area, it probably is. It is actually very challenging to build an entirely waterproof structure.

It would be a mistake to assume that your pool is leaking. You should start at the very beginning and test your pool for evaporation as well as restrict access to the pool for a few days while you determine whether the pool is leaking or not. By using the bucket test you can verify whether the pool is losing more water than just evaporation. Fill a clear plastic container like a juice pitcher and set it on the ladder or steps in your pool such that the water level outside the pitcher and the water level inside the pitcher are exactly the same. Leave the pool for 24 to 48 hours and then note whether the pool water level is lower than the level in the pitcher. Both water levels should be the same if the water loss is from evaporation. If the water level in the pitcher is higher than the pool water level then this points towards a potential leak in the pool.

Can You Ignore A Leak In A Pool?

If you did the bucket test and have determined that your pool is losing water faster than from just evaporation then you should not ignore this problem. Pool systems are designed to be leak free and if you continue to operate your pool with a known leak then you can be sure that further (more expensive) problems will be developing. Moving water erodes soil and damages masonry so you should resolve to fix any leaks in your pool system as soon as you find them. If you want more information on how pool leaks damage pools then you can read this article on why you should never ignore a pool leak.

In some cases the cost of fixing the leak is less than the cost of finding the leak. Pools can leak in a number of different ways and often the only way to find a leak is through a process of elimination style search. This is a process that takes time, and is completed in multiple stages. This is one of the reasons that leak detection services are fairly expensive. In addition to needing multiple trips for most leaks to be diagnosed and repaired, very often pools can have more than one leak location. In the case of multiple leak locations it is most likely that the worst offending leak will be located first, and any smaller leaks will not be found until after the more major leak has been repaired.

How To Find Where My Pool Is Leaking

Why is my pool water disappearing?
Once you have confirmed that your pool is leaking you now begin a process of tests to help you determine which part of the pool system is leaking, and then further testing to find the exact origin of the water loss so you can repair it. This first thing you will attempt to figure out is whether the pool is leaking from the plumbing system somewhere, or from the structure itself. If the pool were empty it would be a lot easier to test the system for leaks since the main drain is located on the floor of the deep end...not such a great location for easy servicing. The problem with this is that you should not drain your pool as there are many types of pools which are not supposed to be drained. All types of pools: concrete, vinyl liner, and fiberglass can be damaged from draining them at the wrong time, or in the wrong way, so do not attempt to drain your pool unless you understand the risks.

The problem with the main drain on the bottom of the pool is that the first step of finding where the pool is leaking is simply to isolate the plumbing system from the pool structure. This will give you a definitive direction to move in with your next leak detection tests. If you can not reach the main drain then this complicates the isolation process. If your pool does not have a main drain then this is certainly an advantage when it comes to finding leaks...possibly the only advantage of your pool not having a main drain. Even without being able to work on the main drain you might be able to test and find the leak in a return line.

Plugging Pool Returns & Skimmer - If you are able to, the ideal way to isolate your plumbing system from the structure of your pool is to plug all the suction and return ports. This includes the main drain if you are able to get to it. If you plug all ports in your pool and the pool continues to lose water then this is a confirmed symptom of a leak in the pool structure somewhere.

Turning Pump On & Off - A simple test for the plumbing system of the pool is to run the pump for 24 hours and record the amount of water the pool loses. Next refill the pool to the same starting point and this time turn the pump off for 24 and record the rate of water loss. If the amount of water that the pool loses is different than with the pump running this points towards a plumbing leak.

The reality of leak detection in pools is that most of the time these tests will not definitively tell you where the leak is. For a lucky few, a simple test or two might point you in the right direction, but there are a lot of examples of how finding pool leaks goes against intuition. For example, if you plug off all ports on your pool and notice that the pool does not lose water, you might assume that this means the leak is in the plumbing and not the structure of the pool. It could be that there is a leak in the pool structure, but the testing plug that you used in the port temporarily blocked the leak giving you the false impression that the leak is not in the structure. Or possibly there has been a lot of rain recently at this has slowed the rate of an underground leak temporarily. Pools also deal with a lot of variable conditions. When testing for pool leaks these variables can sometimes manifest in ways which skews the test results.

Where Do Pools Leak The Most?

Pools tend to leak in certain ways and in certain places and this information is used by leak detection specialists to find pool leaks. The testing process can get you close to the leak location but it is the experience of the person looking for the leak that is most helpful to help interpret the results of the tests properly. If you are a pool owner then you do not have the benefit of years and years of working on swimming pools. Without this experience it makes it harder for you to find leaks in your pool, but not impossible. Here are some of the most common and well known pool leak locations:

Return Pipes - The return lines for pools are a very common leak location. If the pool and the pool return pipes move (settle) in the ground at differing rates this will almost always result in a leak where the return meets the pool wall. This can often be heard with a stethoscope or even just by ear when the line is put under pressure. While breaks, cracks, or collapses in the pipe can happen anywhere, they are most likely to be where joint connections have been made.

Skimmer Pipe - The skimmer line for pools is a known leak point where the pipe connects to the underside of the skimmer. This is inherently a more difficult connection to make than a horizontal pipe connection. Also many skimmers are (and have been) made with ABS material, not PVC, and the transition between PVC pipe and ABS skimmer ports can fail. The underside of a pool skimmer is not conveniently located for service even in the best of circumstances. Concrete pool skimmers are also usually encased in concrete on all sides making the skimmer connection point even harder to get to. Even moderate pool renovations can skip skimmers for this reason so the skimmer on your pool may very well be original to the pool construction.

Skimmer Throat - The point where your skimmer throat connects to the wall of the pool is a well known leak location for all kinds of pools. With a vinyl pool you would likely notice rust staining where the skimmer meets the wall, but a concrete pool is more difficult to spot leaks. Dye testing around the skimmer connection point is one of the best solutions to finding leaks in these locations.

Main Drain - The main drain is also located in an unserviceable location on your pool. This means the main drain line on your pool can be older than other parts of your pool if yours has been renovated. Main drains can leak around the fixture itself, as well as through the suction pipe that connects to them. In addition to this main drains can develop leaks if the hydrostatic relief valve in them fails from rust, or from a rock obstructing the valve from closing properly. Dye testing, pressure testing and visual inspection all require a diver, or to drain the pool to inspect. Since you should not drain a pool this makes leaks in the main drain one of the hardest complicating factors for finding leaks in pools in general. If a pool does not have a main drain then it is much easier to isolate the plumbing system from the pool structure.

Equalizer Line - The equalizer line in the pool is a non pressurized pipe that connects from the main drain to the underside of the skimmer. This would allow water to access the skimmer even if the water level in the pool slipped below the mouth of the skimmer. This pipe is almost always left, even after a major renovation, so leaks in equalizer pipes are one of the most likely suspects with older swimming pools. Plugging the equalizer in the skimmer, and also on the other end in the main drain, can resolve a leak in this location.

Pool Lights - Pool lights are by far one of the worst offending leak causes in swimming pools. The electrical pipe where it connects to the light niche is a known leak problem, as is the electrical pipe itself. These components can be easily broken during installation of the pool or the backfilling stage. Leaks can also develop around the flange or fixture which dye testing can usually identify.

Structure Leaks - Structure leaks in a pool can happen anywhere. If you see a crack in a concrete or fiberglass pool then this would be the obvious first place to investigate if you are losing water. All types of pools can leak around any of the fixtures such as returns, lights and skimmers so if you suspect a structure leak scrutinize these areas the most closely. A vinyl liner pool can develop a leak anywhere it is punctured. This is commonly near where the wall meets the floor, and in the corners of the pool. When you look for holes in a vinyl liner pool you are looking for small half moon shaped imperfections in the vinyl.

If you want to find the leak in your pool then you need to follow a process of elimination style of tests to help lead you down the right path. Knowing how pools tend to leak is important but not enough on its own. While there are some leak detection processes which are not suitable for the average pool owner to do, such as pressure testing, most of the pool leak detection process is small, easily completed steps that anyone can do:

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Why is my pool water disappearing?

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Why is my pool water disappearing?


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Why is my pool water disappearing?


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