The Secret Is Knowing Your Pool’s Volume

Save money on pool chemicals while keeping your water clean and clear all year.
Absolutely,  and it starts with one number: your pool’s volume.

At J Designs Pool & Spa, we’ve helped hundreds of homeowners more accurately balance their water chemistry by teaching them how to calculate their pool’s capacity. This simple step leads to smarter product use, better water quality, and long-term savings.

Why Pool Volume Matters More Than You Think

You can’t treat what you don’t measure. If you’re adding chlorine, pH adjusters, algaecides, or clarifiers without knowing exactly how much water is in your pool, you’re most likely:

• Overdosing, which wastes money and risks damage to surfaces

• Underdosing, which opens the door to algae, cloudiness, and safety issues

Pool volume errors of just 10% can throw off your chemical levels for a week.  That’s why volume accuracy is the foundation of pool chemistry  and a must for reducing your chemical costs.

How to Calculate Your Pool’s Volume

Here are the basic formulas based on pool shape:

Rectangular Pool

Length × Width × Average Depth × 7.5 = Gallons

To calculate average depth:
(Shallow end + Deep end) ÷ 2

Round or Circular Pool

π × Radius² × Average Depth × 7.5 = Gallons

(Use π ≈ 3.14)

Oval Pool

Length × Width × Average Depth × 5.9 = Gallons

Freeform or Kidney-Shaped Pools

Break the pool into sections (like rectangles or ovals), calculate each volume, and add them together.

Pro Tip:   For accurate measuring, insert a pool pole into the deep end; it measures 8' and extends to 16'. Then, remove it from the water and use a tape measure to measure the wet side of the pole.  -You can use the tape alone when you have a diving board, as shown in the picture.

Some apps, like the Orenda Pool Volume Estimator,  simplify math.

How This Helps You Use Less Chemicals

Once you know your pool’s gallon capacity, you can:

• Use exact product doses based on label instructions

• Avoid guesswork and overcorrection

• Catch imbalances earlier, saving time and money on recovery

Most clients see 10–15% savings on chemicals once they start dosing based on volume instead of rough estimates.

Run-Time Matters: Why You Should Adjust Your Pump Based on Pool Size

It’s about how much product you add and how well it circulates.

A pool pump should turn over all the water at least once daily.

Here's a general rule:  Gallons ÷ Flow Rate (GPM) = Hours pump should run daily

For example, if your pool has 20,000 gallons and your pump flows at 50 gallons per minute (GPM):
20,000 ÷ 50 = 400 minutes = 6.7 hours

Pro Tip: Run the pump longer during the summer or heavy use. You can reduce it slightly during winter, but always ensure full circulation for even chemical distribution.

Benefits of Mastering Your Pool Volume

• Clearer water year-round

• More accurate testing & adjustments

• Lower chlorine & pH chemical costs

• Less equipment strain due to balanced chemistry

• Confidence to manage your pool between professional visits

At J Designs, we believe in empowering homeowners with the knowledge and tools to extend the life of their pools and reduce unnecessary costs.  Start with volume to reduce chemical use without compromising water quality.  Understanding how much water is in your pool helps you:

Dose products properly - Run your equipment efficiently - Keep your pool crystal-clear and safe

Use only high-purity products - Base all doses on actual gallons, not estimates

Test the water weekly, especially after rain or heavy use

Brush the pool after adding chemicals or salt - Adjust pH regularly,  high pH = scale and chemical waste

Need help calculating or checking your pool volume? We’re here to help.

Contact us today for a consultation, and let’s get your water dialed in,  brighter, cleaner, and more cost-effective.