Having your pool refilled with fresh water is one of those maintenance tasks that seems straightforward until you check the final price. The cost to refill a pool is not a fixed number, because it depends entirely on the specific circumstances of your installation and your local utility rates. While the price of water per gallon is relatively low, the sheer volume involved in a standard pool means the bill can quickly add up.
Calculating the Price Per Gallon
The foundation of determining your refill cost lies in understanding your local water rates. Water is typically billed in units, often measured in thousands of gallons or cubic feet, and the price per unit varies significantly depending on your region, the time of year, and your specific water district. To calculate the cost accurately, you need to find the "cost per gallon" or "cost per 1,000 gallons" on your recent water bill. Once you have that rate, the math becomes simple: multiply the total volume of your pool (in gallons) by the cost per gallon.
Volume is the Key Factor
Before you can apply the water rate, you must determine how many gallons your pool holds. This calculation changes dramatically based on the pool's shape. A basic rectangular pool uses the formula Length x Width x Average Depth x 7.5. For a round pool, the formula is Pi x Radius Squared x Average Depth x 7.5. Because few pools are perfect geometric shapes, you often have to calculate the volume of different sections separately and then add them together. The average depth is crucial; it is found by adding the shallow end depth and the deep end depth and dividing by two.
Typical Costs for Common Pool Sizes
To give you a practical sense of the financial impact, here is a breakdown of the refilling costs for common residential pool volumes, based on a hypothetical average water rate. While your specific bill will differ, this table provides a realistic benchmark for budgeting.
| Pool Size (Gallons) | Estimated Refill Cost |
|---|---|
| 10,000 gallons | $75 - $150 |
| 15,000 gallons | $110 - $225 |
| 20,000 gallons | $150 - $300 |
| 25,000 gallons | $190 - $375 |
| 30,000 gallons | $225 - $450 |
These figures assume a water rate of roughly $0.0075 to $0.015 per gallon, which is common in many urban and suburban areas. As you can see, refilling a 20,000-gallon pool can easily cost between $150 and $300, making it a significant monthly expense depending on how often you need to do it.
Why Water Levels Drop
Understanding why you need to refill the pool helps contextualize the cost. Evaporation is the primary culprit, particularly during hot, sunny, and windy weather. A standard uncovered pool can lose up to a quarter of an inch of water per day. Splash-out caused by swimmers is another major factor; the more active the pool, the more water displaced. Leaks, while less common, can cause a rapid and significant loss of water, which requires immediate attention from a professional to repair.
Strategies to Minimize Refill Frequency
Because the cost of water can accumulate, many pool owners look for ways to reduce how often they need to refill. Investing in a high-quality pool cover is the single most effective strategy, as it can reduce evaporation by up to 95%. Regularly checking for leaks by performing the bucket test can save thousands of gallons of water over time. Additionally, adjusting your fill level slightly lower or topping off the water weekly with a garden hose, rather than waiting for a catastrophic drop, can help you manage the total volume of water used over the season.
The Hidden Costs of Draining
If you are calculating the cost to refill, you should also consider the expense of draining the old water. In many municipalities, draining pool water into the storm sewer system is either prohibited or requires a special permit and fee. If you are allowed to drain it onto your lawn, the high mineral and chemical content of pool water can kill grass and plants, essentially turning your landscaping into an additional cost center. Professional waste removal services are an option, but they add a significant disposal fee to the total project budget.
