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Calculating Water Loss from a Pool Leak: A Simple Formula

On Jul 17, 2017

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Knowing how much water loss your pool is experiencing on a daily basis is an important aspect of pool ownership. Calculating water loss from a pool leak is not difficult with the standard formula.

Before you calculate the total estimated water loss, you'll need to perform a bucket test to determine the number of inches of water lost in a 24 hour period. The basic bucket test will tell you approximately how much water you are losing each day in inches. A quarter-inch is normal for evaporation. A pool or spa tub will lose less if it is covered when it is not used. You can access our bucket test instructions here.

Pool Water Loss Formula

Multiply the length (L) times width (W) times the amount of the water loss (WL) in inches times .6233 for a rectangular pool. 

Example: L-32' x W-18' x WL 2" x .6233 = 718.04 gallons in 24 hours.

                 L-40' x W-20' x WL 1.5" x .6233 = 747.96 gallons.

For circular pools or hot tubs, multiply the diameter x diameter x WL x.48929.

Example: D-12' x D-12' x WL 1.5" x .48929 = 106.6 gallons in 24 hours.

Divide the daily loss by 24 to get the hourly rate. In the example above, the 32x18-foot pool is losing almost 30 gallons an hour. That is a substantial waste of water that can soak the ground and lead to other problems. The loss becomes expensive when you are constantly refilling the pool.

Many pools are oval shaped or freeform designs. You know how much water your pool holds when it is filled to the recommended waterline. This formula gives you an approximation of the water loss.

The amount of water loss is an indication of the size of the pool leak. A slow loss of a half-inch per day suggests a leak in the skimmer basket. Larger water loss may indicate a leak in the plumbing system or a crack in the pool surface. Pool leaks do not go away on their own. The spa or pool leak has to be located and repaired.

Signs You Have a Pool Leak

  • Your pool loses more water than regular evaporation (about 1/4 inch)
  • The pool has air in the system
  • Equipment loses prime
  • You see cracks
  • Pool deck is sinking or lifting
  • There are soggy spots around the pool
  • You add water more than once a week

Finding the Leak

A leak close to the surface of the pool will stop as soon as the water level falls below the leak spot. Check all fittings near the water line where metal meets the pool surface. They must be tight to prevent leaks. Check for loose tiles around the water line

The leak will stop if the water is at the bottom of the skimmer basket area if this is the problem. The intake line will suck in air which is harmful to the filter and pump motor. Check the skimmer basket and make sure it fits tightly against the wall. The intake plumbing line may be the cause of the pool leak.

Tears in vinyl pools are often easy to locate. Check the wall surface for any possible tear and repair it immediately. Check for cracks in the surface of cement and gunite pools. The drain needs to be checked in all pools. This should also be a tight fit since it leads to one of the intake lines.

The water level in a spa tub must always be above the intake line and the return jets. A water level below the intake pipe is an indication of a leak. All of the pipes should be checked in a stand-alone spa tub when you suspect a leak.

Water on the decks and ground surrounding the pool indicate a break in the plumbing lines. Aquaman Leak Detection has a unique ultrasound system that will pinpoint the leak without tearing up the deck. The pipe, usually a PVC tube, can be easily repaired to stop the pool leak.

Call Aquaman Leak Detection if your pool is losing water. We will find and repair the leak with fast and efficient service. Headquartered in Brevard County we serve all of Florida.

This article was originally published in July 2017 but has been updated for accuracy and freshness.

Swimming Pool Leak Water Loss Calculator


By Aquaman

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