Filling your pool with water is a significant milestone whether you’ve just installed a new pool or are preparing an existing one for the season. While it might seem like a simple process — after all, it’s just turning on a hose — there’s much more to it than meets the eye. This critical phase not only sets the foundation for the entire season but also plays a key role in maintaining clean, balanced water and preventing damage to the pool structure and equipment.
In this guide, we’ll walk you through the essential actions you must take as soon as you start putting water into your pool. From preparing your equipment to testing your water chemistry and ensuring the integrity of your pool surfaces, this comprehensive, step-by-step breakdown will help you make informed decisions and avoid costly mistakes.
1. Pre-Filling Inspection and Preparation
Before you actually start filling your pool, it’s important to complete a series of inspection and preparation tasks. These steps are crucial for making sure that everything runs smoothly once the water starts flowing.
1.1 Check Pool Structure for Readiness
If it’s a new installation, ensure the pool structure has properly settled. Ground movement or settling can create stress points in the shell or liner. If you’re using a vinyl liner pool, confirm that the vinyl is snug and free of wrinkles or tears. For concrete or fiberglass pools, scan for any hairline cracks or surface imperfections.
1.2 Verify Pool Equipment Installation
Make sure that the following equipment is installed and positioned correctly:
- Pump and filter system
- Skimmer and return jets
- Plumbing connections
- Drain lines (if relevant)
Ensure that all connections are tight and that no leaks are visible. Your equipment should be completely installed before filling begins to minimize risks.
1.3 Install Safety Features
Before water is introduced, you must also have safety features in place. This includes:
| Type of Pool | Safety Requirements |
|---|---|
| Inground pools | Pool cover, fencing, door alarms, or automatic safety covers |
| Above-ground pools | Secure ladders, barriers, or locks |
These measures ensure compliance with local safety codes and protect children or pets during the filling and afterward.
2. Begin Filling the Pool
Once you’ve completed your pre-filling preparations, it’s time to start filling. The method you use will depend on your water source and local regulations.
2.1 Water Sources and Options
There are several options for pool filling:
- Municipal water supply (via hose or direct line connection)
- Well water (confirm that it’s safe for swimming pools)
- Water delivery service (ideal in drought-prone areas or when rapid filling is necessary)
Using city water is the most common approach. A standard garden hose from a household outdoor spigot can fill an average-sized pool in 24–48 hours.
2.2 Monitoring the Water Level During Filling
As water begins to flow, monitor the rate, and keep an eye on the pool shell. Rapid filling can create stress or destabilize the structure. If you are using a main drain to assist in the filling process, make sure the pump is off during filling unless specifically directed by the manufacturer.
Key Tip: Start filling at a time when you can monitor the process to avoid overflow. Some municipal water companies even offer a special rate or reduced fee if filling is done off-peak hours.
2.3 Protecting Your Pool Surface
For vinyl and fiberglass pools, water should never be allowed to stagnate without a complete cover. If possible, cover the unfilled sections until all water is added, especially outdoors where debris can enter the pool when it’s only partly filled.
Concrete and gunite pools, in contrast, require a period of conditioning once filled. This step, known as “balancing the startup water,” is essential and will be discussed in more detail below.
3. Initial Water Testing and Balancing
Once the pool reaches the proper water level — typically at the midpoint of the skimmer — it’s time to conduct initial water testing and begin balancing for safe, stable conditions.
3.1 Understanding Key Water Chemistry Parameters
There are six major water chemistry factors to monitor and adjust when first filling a pool:
| Parameter | Recommended Range | Why It Matters |
|---|---|---|
| pH | 7.2 – 7.6 | Determines water comfort and sanitizer efficiency |
| Alkalinity (TA) | 80 – 120 ppm | Helps buffer pH and keep it stable |
| Calcium Hardness | 200 – 400 ppm | Prevents corrosion or scaling of surfaces |
| Cyanuric Acid (CYA) | 30 – 50 ppm | Protects chlorine from UV degradation |
| Chlorine | 1 – 3 ppm | Sanitizes water and controls algae and bacteria |
| Total Dissolved Solids (TDS) | Under 1500 ppm | High levels can cause water clarity issues |
3.2 Test Kits: Liquid vs. Strips
When testing the water for the first time, accuracy is important. Use either:
- **Liquid test kits** (Taylor Technologies is a trusted brand)
- High-quality **digital test strips**
These give more reliable results than basic pool test strips found at big-box stores. If you’re uncomfortable testing yourself, bring a water sample to your local pool store for a detailed reading.
3.3 Adjusting Water Chemistry after Filling
After you’ve recorded your initial test results, you’ll need to adjust the water chemistry to meet the ideal levels before starting to circulate and sanitize the pool.
For example:
| If Test Shows | Action Required |
|---|---|
| pH too high | Add pH reducer (sodium bisulfate or muriatic acid) |
| pH too low | Add pH increaser (soda ash) |
| Alkalinity low | Add alkalinity increaser (sodium bicarbonate) |
| Calcium hardness too high | Dilute water or use sequestering agents |
Concrete pools also often face high alkalinity and calcium from new surfaces — a process known as new pool start-up. It’s often recommended to acid-wash new plaster pools or perform a “bake” procedure to allow the calcium to release before balancing.
4. Starting the Pool Equipment
With the water chemistry tested and adjustments made, it’s time to start up the pool plumbing and filtration system.
4.1 Priming the Pump
Before you open the filtration system, you must prime the pump. Most pool pumps require that water be manually introduced into the pump basket to remove air and allow proper impeller function.
Steps to prime the pump:
- Turn off the pump
- Remove the pump lid and basket
- Pour pool water or clean garden water into the pump
- Replace basket and secure lid
- Turn the pump ON
Watch for backpressure or loss of prime — signs that the system is not pulling water correctly.
4.2 Circulating and Filtering the Water
After the system is primed, begin a full filter cycle. For a new or seasonal start-up, run the pump 24/7 for the first week to ensure thorough filtration and chemical circulation.
4.3 Backwashing or Cleaning the Filter
Wait until the pressure gauge rises ~8–10 PSI above the clean starting pressure before backwashing a sand or DE filter. Cartridge filters will need physical cleaning under a strong stream of water.
5. Water Sanitation and Algaecide Applications
Your next step is to begin sanitizing the water and taking steps to prevent algae from taking hold.
5.1 Adding Chlorine to Start the Sanitization Process
The most common form for startup is liquid chlorine or chlorine tablets. For a startup, consider using liquid chlorine because it dissolves immediately and allows precise additions.
The initial dose may be a “shock” or superchlorination to get ahead of any bacteria or organics that might have entered during the filling process.
Tip: Add chlorine either early in the morning or after sunset for minimal UV degradation — and always wear protective gloves and eyewear.
5.2 Using Algaecide as a Preventative Measure
Algaecide isn’t a replacement for chlorine but acts as a backup. It’s best used once the chlorine level is stable and balanced. For new pools, it can help prevent biofilm or algae growth from emerging in the fresh water.
5.3 Monitor Chlorine and CYA Levels Daily
Once sanitizers are added, monitor daily. The balance between free chlorine and CYA is important — especially if using stabilized chlorine. Some startup water may have high CYA due to source water or the use of dichlor/trichlor tablets.
6. Skimming and Vacuuming the Pool
As your circulation system starts working, you may notice the accumulation of floating debris or settled sediment on the bottom of the pool.
6.1 Start Skimming Immediately
Floating debris like leaves, dust, and pollen should be skimmed out within the first 24 to 48 hours. A telescopic pole and a leaf net make this task easy and efficient.
6.2 Vacuuming the Pool Bottom
Sediments and fine silts may not pass through the filter efficiently. Vacuuming to waste (if available) or to the filter on a high setting can help remove particulates faster.
6.3 Consider Using Pool Clarifiers
To help speed up clarity, pool clarifiers can be added after proper chlorine and balance levels are achieved. These agglomerating agents help your filter catch finer particles.
7. Establishing a Consistent Maintenance Schedule
After the water has been filled, filtered, and tested, it’s time to shift into regular maintenance.
7.1 Creating a Weekly Maintenance Routine
A solid weekly routine generally includes:
- Testing pH and chlorine with adjustments as needed
- Skimming debris and brushing walls and floor
- Vacuuming once per week unless water is excessively dirty
- Backwashing or cleaning the filter as needed
7.2 Automating Where Possible
Consider using digital controllers, saltwater chlorinators (if compatible), or automatic pool cleaners to reduce manual labor requirements as your pool is now set up.
7.3 Documenting Your Water Chemistry
Using a journal or an app to document daily readings and chemical additions can help you better understand how your water behaves weekly or seasonally — and help avoid recurring imbalances.
8. Watch for Common Issues During the Initial Weeks
The first 21–30 days after filling are when your pool is most vulnerable to chemical imbalances, biological growth, or scaling.
8.1 pH Imbalances
Concrete surfaces can leach lime into the water, raising pH and alkalinity. Regular testing and small acid additions (if needed) can prevent this from becoming a bigger issue.
8.2 Metal Leaching and Staining
If your water source is high in metals like iron or copper, you may begin seeing discoloration or staining within the first few weeks. Use a metal sequestrant when filling to combat this.
8.3 Algae Spikes
Even with chlorine, new water can still be vulnerable during the startup period. Keep free chlorine levels stable and use preventative algaecides for the first 3–4 weeks.
Conclusion: A Clean, Balanced Start Ensures Full-Season Success
Properly managing the process of filling your pool is one of the most important steps toward ensuring clear water and a long season of swimming. From inspecting equipment and starting up your pump, to balancing water chemistry and implementing daily maintenance practices, each of these actions contributes to the health and longevity of your pool.
By taking the time to do it right from the very first drop of water, you minimize the need for corrective treatments later, preserve your equipment, reduce long-term maintenance costs, and ultimately enjoy a pool that’s clean, comfortable, and worry-free.
So whether you’ve just installed a brand-new pool or are opening an existing one for the year, use this comprehensive guide to make informed, timely decisions that will set the tone for a successful season.
Should I test the water immediately after filling the pool?
Yes, it’s essential to test your pool water as soon as it’s filled to ensure it’s chemically balanced and safe for swimming. When you first put water in a pool, the source water may contain impurities, minerals, or pH levels that are not ideal for pool use. Testing the water allows you to determine the levels of pH, alkalinity, calcium hardness, and chlorine, so you can adjust them accordingly.
You can use test strips or a liquid test kit for accurate results. Once you have the readings, adjust the pH to the recommended range of 7.4 to 7.6, and balance total alkalinity between 80 and 120 ppm. These initial adjustments help prevent staining, scaling, and discomfort for swimmers.
How long should I wait before adding chemicals to a newly filled pool?
It’s a good idea to wait at least 20 to 30 minutes after filling the pool before adding chemicals, especially if your pool has a circulation system. Waiting allows the water to circulate slightly and enables any sediment or stirred-up particles to settle. However, it’s best to confirm that the water is circulating before adding any chemicals to ensure they disperse evenly.
Once the pump is running and the water is stable, you can begin treating the water based on your test results. Start with adjusting pH and alkalinity, then move on to sanitizer levels like chlorine. This step-by-step process ensures optimal chemical effectiveness and helps avoid potential imbalances or damage to the pool surfaces.
Is it necessary to shock the pool when first filling it?
Yes, shocking the pool when you first fill it is a crucial step in establishing a clean and balanced water environment. Municipal or well water used to fill the pool may contain organic contaminants or metals, and shocking ensures any bacteria, algae spores, or other impurities are eliminated from the start.
Use a chlorine-based shock (unless your water source is high in cyanuric acid) and follow the manufacturer’s instructions carefully. Run the pool pump for at least 8 to 12 hours afterward to ensure thorough circulation. This initial shock treatment sets the stage for healthy water and makes it easier to maintain proper chemical levels moving forward.
What should I do if my pool water is cloudy after filling?
Cloudy water after filling your pool may be due to high levels of minerals, fine particles, or an imbalance in water chemistry. Start by testing the water for pH, alkalinity, and hardness to see if adjustments are needed. Often, a pH imbalance can cause cloudiness, so correcting that first may help improve clarity.
If the water chemistry is balanced, consider using a water clarifier or pool filter enhancer to help the filtration system trap suspended particles more efficiently. Also, ensure your filter is functioning properly and clean or backwash it as needed. Persistent cloudiness may indicate the need for a metal remover, especially if you filled the pool using well water.
How often should I check the water chemistry in the first week after filling?
During the first week after filling your pool, it’s best to test the water daily to monitor chemical levels and make any necessary adjustments. This frequent testing helps stabilize the water chemistry and prevents potential issues like scaling, staining, or cloudy water before they become more serious.
Once the water stabilizes and remains balanced for a few days, you can reduce testing to 2 to 3 times per week. Keep a detailed log of your readings and any chemical adjustments made. Regular monitoring and maintenance are key to keeping your pool clean, safe, and ready for use over time.
Do I need to add algaecide when I first fill the pool?
Adding algaecide when you first fill your pool is not mandatory, but it’s a smart preventative measure to inhibit algae growth, especially in warm or sunny climates. Algae can begin to develop quickly in untreated or improperly balanced water, and algaecide adds an extra layer of protection.
Use a quality, non-quaternary algaecide (such as a copper-based or polyquat formula) to support chlorine in keeping the pool algae-free. Always follow the product instructions and avoid overuse, which can cause foaming or staining. Algaecide should be used in tandem with proper filtration, circulation, and sanitizer levels, not as a substitute for them.
Why is brushing and vacuuming important after first filling the pool?
Brushing and vacuuming the pool after it’s filled removes any small particles, dust, or debris that may have settled on the walls and floor during the filling and chemical treatment process. Even if the water looks clean, microscopic particles and dust can affect water clarity and chemistry if left to accumulate.
Additionally, brushing helps prevent algae growth by removing any spores that may begin to cling to pool surfaces. Vacuuming ensures that loose material is removed completely, especially before turning on the filtration system. This initial cleaning step contributes to a cleaner filtration process and makes it easier to maintain sparkling water from the very start.