Pool Losing 1 Inch of Water a Day: Is This Normal?

Pool Losing 1 Inch of Water a Day

It is normal for a pool to lose water over time due to evaporation, so there’s nothing wrong with having to add water to your pool every now and then. Under normal conditions, you should be adding water to your pool every 7-10 days. If you find yourself refilling the pool more often than that, then that might be indicative of a problem.

The rate of water loss is affected by factors such as temperature, humidity, wind conditions, use of a pool heater/cover, water getting splashed out, or there may be a water leak.

A good rule of thumb is that you should expect a drop in water level of a quarter of an inch in a day in a humid environment, or half an inch a day in a dry one. If your pool is left uncovered in 100 degree weather, you can expect to lose a full inch of water in a day. If your pool is losing an inch of water a day, then the rate of water loss is quite severe and some action should be taken on your part to stop this rapid water loss.

How can you tell if your pool water is naturally evaporating, or if water is being lost due to a leak? And even knowing that water evaporates naturally, how can you still keep your pool’s water level from dropping by an inch or more a day? Find out the solutions below.

How to determine if your pool has a water leak

The goal of this section is twofold. First, we want to identify if there is a leak at all. Second, we want to pinpoint where exactly the leak is coming from. Once we have these pieces of information, we can fix the pool ourselves or call a professional to do it for us.

The bucket test

The easiest test to determine if your pool has a water leak is the bucket test. As the name suggests, you’ll need a bucket to help you with this test.

  1. First take a bucket and scoop up some of your pool’s water with it.
  2. Place the bucket on the steps of your pool, making sure that the top of the bucket is above the water level. The goal is to put the bucket in identical conditions as the pool, so why not literally put it in the same conditions.
  3. Mark the pool’s water level and the water level in the bucket.
  4. Wait a minimum of 24 hours, or a few days if you want.
  5. After waiting, compare how much the water level has dropped in your pool since the start of this test compared to in the bucket. If both the water level in the pool and the bucket dropped by a similar amount, then there is no leak, and the water loss was due to evaporation. If the water level in the pool dropped significantly whereas the water in the bucket didn’t, then your pool may have a leak.

So now you know your pool has a leak, but we need to find out where it’s leaking from. These next tests can help you.

Running your filter

A common source of the water leak is your pool filter. Measure the difference in the pool water level while letting it run for 24 hours. Then measure the difference after keeping the filter system off for 24 hours.

If you notice there is greater water loss when the filter is running, then chances are the leak is coming from the pressure side of the plumbing system, behind the impeller of the pump.

Conversely, if more water is lost when the filter is off, then the leak is coming from the vacuum side of the plumbing system, before the impeller of the pump.

If your pool is losing the same amount of water regardless of whether the filter is running or not, then the leak is likely coming from the swimming pool itself.

Leaks due to structural damage

If you’ve narrowed down that the leak is due to structural damage, then we can further pinpoint where the leak is coming from using food coloring.

Squeeze a few drops of food coloring in the pool water, around areas where you suspect the leak is. Follow where the colored water is flowing to, and you will find the source of your leak.

The most common reason why you might be losing 1 inch of water or more a day is due to skimmer leaks. These can be easily patched up with pool putty. You can also fix leaks with a vinyl liner patch kit.

Leaks can also occur from any of the fittings (lights, returns), cracks in the pool liner, cracks in the pool liner, pipes, and so on.

If you feel like fixing a water leak is way over your head, then consider hiring pool professionals to locate the leak and fix it for you. This may save you more money and headaches in the long run if you don’t know how to fix the leak on your own.

How much water loss in a pool is normal?

Most of our article has focused on detecting pool leaks, however water can be lost naturally due to evaporation or frequent use. In this section, we detail some of the “natural” reasons why your pool might be losing 1 inch of water or more in a day.

  • Temperature: The hotter the temperature, the more quickly water evaporates. At outdoor temperatures of 100 degrees or more, you can expect your pool water level to decrease by 1 inch a day. At only 80 degrees, the rate of water loss is around 0.25 inches a day, a much more acceptable rate of water loss.
  • Humidity: The more arid the air, the faster water evaporates, and the more humid it is, the slower. Pool owners living by the coast should not expect much water to be lost due to the humidity, perhaps 1 inch per month.
  • Wind: Closely related to humidity is the wind condition. The windier it is, the more quickly pool water will evaporate. On a windy day, you can expect your water level to decrease by 0.5-1 inch per day.
  • Lack of pool cover: Temperature, humidity, and wind can cause your pool water to evaporate rapidly, but that is only assuming that your pool is not covered up. If your pool doesn’t have any leaks and it is covered up, you can significantly reduce water loss.
  • Splashing: If you or other pool guests are splashing a lot of water out of the pool, then obviously the water level will drop. Typically, the more people there are in a pool, and the more frequently it is used, will cause your pool to lose water. Expect to lose as much as 5 inches of water or more a day if guests are constantly splashing.

How often do you add water to your pool?

A normal rate of water loss assuming normal conditions is 0.25 inches a day. That means the weather is fair, the humidity is not too high or low, and there is little to no wind. Under these idyllic conditions, you can expect to add water to your pool every 7-10 days.

However, we discussed many factors that can cause your water to evaporate rapidly. Yes, high temperatures can cause your pool water to evaporate, but that is also the best time to actually use the pool. So you’re just going to have to refill the pool water faster during hot days. You may need to add water back as soon as 3-4 days instead.

One factor we did not mention yet is rain. If it rains frequently where you live, the rainwater can replenish the water that was lost on other days. In fact, if it rains too much you may need to drain some of the excess water out. Depending on how much rainfall you get each week, you may not even need to add water to your pool, or much less than you think.

If your pool isn’t being used, then it’s best to leave it covered up. The pool cover can prevent water from evaporating so that you don’t need to fill up your pool as often.

Losing an inch of water a day from your pool is not necessarily indicative of an issue now that you’re aware of the various factors that can cause water loss. Unless you have a pool leak, you need to consider using your pool cover more often, letting rainwater replenish any lost water, and telling your guests not to splash so much.