Peter Spirito - How Much Water?

How much water should my swimming pool use?

As a building inspector assigned to inspect swimming pools under construction I am frequently asked; "How much water should I have to be adding to my pool every week?" Or;" it seems I am always putting more water in my pool. Could my pool have a leak?"

The amount of water that needs to be added to your swimming pool each week depends on the time of the year, the frequency and type of use, and if there are any leaks.

In South Florida a swimming pool used by adults only, will lose between 1" and 1 1/4" per week in the summer. Much of the water evaporated by the summer heat is replaced by the frequent rains that occur during the summer months. In the winter months, even though the temperature is cooler, that same pool will lose between 1 1/4" and 2" per week because there is less rain. A swimming pool used by a group of children can easily drop 2 inches in one day.

Having the correct water level is important to the proper functioning of the pump and filtering system. The correct water level for a swimming pool is 1/2 way up on the skimmer opening in to the pool. If the water level is too high the skimmer is unable to trap and hold floating debris such as leaves and insects. If the water level is too low, again the skimmer will not work and there is the added problem of air entering the water piping system and causing the pump to cavitate. Pump cavitation is caused by air entering the plumbing system and interrupting the water flow. When standing next to your pool pump while it is running the motor should have a constant steady sound and the water flowing thru the pump will also be steady with very few bubbles. When the water level is too low, the pump sucks in air and cavitates. This creates a whooshing sound both at the pump and at the pool outlets. What is happening is that the flow of water to the pump has been interrupted and the pump has run dry for a few moments. Over time this will damage the pump.

Many swimming pools have an automatic water filling feature called an auto-fill. This auto-fill is identical in operation to a toilet tank in that there is a float valve that will automatically allow fresh water to enter the pool whenever the water level gets low. When the pool refills to the preset level the float valve is set at, the water shuts off. The down side to an auto-fill is that if you have a leak the auto-fill keeps refilling the pool and you never become aware of the leak. Only a large leak that greatly impacts your water bill may draw your attention. To know if you have an auto-fill look at your pool deck. Most auto-fills are installed recessed in to the pool deck just like your skimmer is and has a similar round cover. Unlike the skimmer, the auto-fill does not have the large opening in to the pool that the skimmer has. Opening this cover will reveal the auto-fill float valve.

It is not difficult to check your swimming pool for leaks. First, if you have an auto-fill it must be turned off. There will be a supply shut off valve, usually located next to the house, where the auto-fill can be turned off. You can verify the auto-fill is turned off by removing the auto-fill cover and gently pushing down on the float valve. If the supply valve has been turned off then no water will be heard passing through the auto-fill and into the pool.

Next take a white plastic bucket and place it on the top step of the swimming pool and fill it with pool water, so that the level of the water in the bucket is exactly the same as the level of the water in the pool. Over the next several days do not use the swimming pool. Monitor the evaporation of both the pool water and the bucket water. If the pool water is lower than the bucket water, you have a leak. If the bucket water is lower than the pool water the auto-fill was not turned off. If the pool water and the bucket water are the same then everything is just fine.

Most swimming pool leaks are not difficult to find and repair for a professional leak detection company, but are nearly impossible for a homeowner to find and repair.