Best Time to Run Pool Pump: Is Night Better?

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What is the Best Time to Run Pool Pump?

The filtration system is the key to keeping your pool clear, clean & safe. And the pool pump is at the heart of it! You need to run the pool pump for around 8 hours a day, but what is the best time to run pool pump?

Best time to run pool pump is late evening. But you could run your pool pump 4 hours at night and 4 hours in the day to maximize the benefits and convenience!

This way the pool pump gets a well deserved break too!

I am aware that the above may be somewhat controversial. There are people who strongly advocate running the pump at night. But there are others, who insist that day is the best time to run the pool pump.

Both sides have valid arguments in their favor. In this post I will explain the benefits of running the pump at night as well as the benefits of running it during the day.

I will also explain why it is best to run the pool pump in two shifts. One shift in the night and another in the day. 

How Many Hours a Day Should You Run a Pool Pump?

So even before you decide when you should run the pool pump, night or day, you must know how long you need to run the pool pump in a day.

The thumb rule is 8 hours a day. 

To ensure that your pool is clear, clean & safe, it is important that the entire volume of water in your pool is circulated at least twice a day.

If the pool filtration system, namely the pump and the filter, has the capacity to move the pool volume every 4 hours then you need to run your pump for 8 hours a day.

As an example, if you have a 20,000 gallon pool then your pump should have a capacity of 5,000 gallons per hour or 85 gallons per minute (GPM). You would need to run the pump for 8 hours to circulate the entire pool volume, twice every day.

The Benefits of Running the Pool Pump at Night!

Following are the benefits of running your pool pump at night

Make the most of Shock!

Of course you need to shock your pool if you witness unusual growth of algae or an “algae bloom”. Regardless of the algae status in your pool you must shock your pool once every week.

There are different types of shocks available but it is best to use an “un-stabilized” shock as it does not raise the Cyanuric Acid (CYA) level in your pool. Liquid Chlorine (Sodium Hypochlorite) and Cal Hypo (Calcium Hypochlorite) are un-stabilized shocks.

Cyanuric Acid (CYA) levels are important as CYA protects the Free Chlorine (FC) from the UV radiation in sunlight. However, shock is a very strong dose of chlorine. It will raise chlorine levels to at least 10 ppm (usually 25 ppm).

Using a “stabilized” shock  such as Dichlor is not a good idea as Cyanuric Acid (CYA) levels can go up significantly. The Free Chlorine gets spent in killing algae or gets decimated by the UV rays. The CYA stays on and accumulates in the pool.

Shock in the Evening!

So, the best time to shock a pool is in the evening using an “unstabilized” shock. Run the pool pump and filter for 4 hours with the Multiport Valve setting on Recirculate position. 

The shock will get broadcast through the entire pool. The Free Chlorine does not need the protection of Cyanuric Acid (CYA) as there is no sunlight. The Filter does not get overloaded with debris or dead algae as the filter is on Recirculate and the pool water is bypassing the filter.

By morning the Free Chlorine would have killed most of the algae. The remaining Free Chlorine will be destroyed by the sun’s UV rays. All in all, your pool should be ready for swimming!

So it is a good idea to shock and run the pool pump at night!

Save on Pump Running Cost!

Utility companies do not charge the same rate for electricity consumed throughout the day. The rate depends on the “Time Of Use”. The Off Peak rate (Night) may be just 2/3rds of the Peak rate (Day).

For a 1 HP pool pump, you could save over $300 per year by running the pump at night rather than in the day. 

Let me show you the maths!

Pool Pump Rating  1 HP = 1.72 kWh. Running for 8 hours per day consumes 1.72X8 = 13.76 kWh per day. Running for 365 days in a year consumes 13.76X365 = 5022.40 kWh.

Just as an example let me take the Peak Rate (during Day) to be 18 cents per kWh and the Off Peak Rate (during Night) to be 12 cents per kWh.

So if you run the pump only during daytime the cost is 5022.40X0.18 = $904.03 but the cost of running the pump only at night is 5022.40X0.12 = $602.69. A saving of $301.34!

The Benefits of Running the Pool Pump at Day!

There are advantages to running the pool pump and filter during the day too!

Filter when Pool Usage is High!

The pool pump sucks in the water through the skimmer and gets floating debris like leaves and bugs filtered out. Clean water is returned to the pool.

Most folks, especially those with kids, tend to use the pool the most, during the day. You want clear, clean water at that time. So running the pool pump when you and your family makes a lot of sense!

Disperse the Chlorine!

To keep your pool sanitized you are likely to be using Trichlor chlorine tablets in the skimmer, floater or feeder. Without good water circulation, the chlorine will be very concentrated near the source but very low in other parts of the pool.

For best sanitization, the Free Chlorine (FC) should be 2-4 ppm, evenly across the pool. Higher levels will result in red eyes and burning skin. Lower levels will encourage pathogens & algae to grow. 

As neither are good, run the pool pump during the day when swimmers are in the pool. 

Cool the Pool!

During summer, the midday sun can get the pool pretty warm due to radiation from the sun and the warm air above it. The temperature at the bottom of the pool, especially for inground pools, is lower as it is in contact with the colder earth.

By running the pool pump at day and ensuring good circulation, you are in effect mixing up the warmer water in the top layer with the cooler water in the bottom layer.

The pool will be cooler and more pleasant during summer, with the pool pump running during daytime.

The Conclusion

For effective filtration & sanitization, the pool water should be turned around two times in a day. The pool pump, with the right capacity, will do this in 8 hours at a stretch or in two 4 hour shifts.

Run the pool pump for 4 hours in the night, during off-peak hours to save on electricity. Pool chemicals such as shock will get broadcast across the pool. Debris will get filtered out so that your pool is clean for a morning swim!

Run the pool pump for 4 hours in the day, when most swimmers are in the pool. Free Chlorine (FC) will be spread evenly, contaminants added to the pool will be filtered out and the pool will be cooler for maximum enjoyment!

Recommended Pool Pump & Sand Filter

Best Pool Pump

The Hayward Super Pump large-capacity, technologically advanced pump blends cost-efficient design with durable construction, setting the standard for excellence and value. 

Super-sized 110 cubic-inch basket has extra leaf-holding capacity and extends time between cleanings. Rigid construction with load extender ribbing assures free flowing operation for heavy debris loads.

The Hayward Super Pump features a large see-through strainer cover, a super-size debris basket, and an exclusive service-ease design for extra convenience.

Hayward W3SP2610X15 Super Pump Pool Pump, 1.5 HP

Best Sand Filter

The Hayward Pro Series Sand Filter for in-ground swimming pools will provide you with hassle-free, effective filtration. The weather-proof tank is constructed of a tough, color-fast polymeric material.

Even water distribution over every square inch of sand is ensured by an integral top diffuser, self-cleaning under drain and 360 degree slotted laterals. Advanced full-flow technology reduces energy costs by achieving excellent filtration, so you can run your filter less.

Thorough backwashing allows for crystal-clear water. Filter is complete with tank, 7-way multi-port valve, sight glass and pressure gauge. 7-way Valve Positions: Filter, Waste, Winter, Closed, Backwash, Recirculation, Rinse.

Hayward Pro Series Pool Sand Filter

Thank you very much for reading the post. I do hope you found it informative and helpful.