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DOE 2021: Learning to Live With Lower Pool Flow Rates

It’s 2021, and that means it’s time to start dealing with low flow. No, we’re not talking about a visit to the doctor—we’re talking about pool pumps.

Starting in July 2021, all new pumps will have to meet updated pool pump energy standards. This has the great benefit of lowering energy usage and costs associated with pool pumps. But it is still a change, so it will require some adjustments for pool care overall.


For years, the most energy-efficient pumps have been variable speed models. Unlike a typical pump, a variable speed pump (VSP) has much more control over the flow rate. By running at a lower RPM, the VSP saves energy—among other benefits.

Technically, the new DOE pump regulations do not specifically require a VSP, or outlaw single-speed pumps. But the vast majority of pumps that meet the new requirements for in ground pools will be VSPs.

This might feel like an about-face if you are used to high flow all the time. Let’s face it, in the USA we are all about bigger is better. More horsepower! More flow! *insert aggressive animal sounds* Pools built in the USA historically trend towards high flow rates, moving lots of water, and high turnover. 

While VSPs are not new, many pools have not made the switch and have stuck with single-speed high flow pumps. These pumps have existed for a decade but even now maybe 40% of pools are being built with a VSP. Things are changing though, and it’s time to make some mental adjustments for what it will mean to operate a pool with lower flow.



Better Filtration

The great news is, it turns out that running at a lower flow rate has great benefits for keeping the water clean. Pool pros have known for a long time that filters generally perform better when you slow the water down. 

A lower flow rate leads to better filter performance. More debris is filtered out with each pass, and the particulate level removed is maximized. We asked pool pros about this effect and their response was “yeah, it’s just physics.”

The filter is often overlooked as a key to clean water. Our attention turns to chemicals when we think of clean water. Sanitize it, shock it, chlorinate it to keep the pool clean, right? But a filter does what no chemical can do by physically removing solids from the water. 

This keeps the water cleaner and removes matter from the main body of water. The more the filter removes, the better the chemicals will actually perform.

More Time To Sanitize

Let’s talk about another side benefit of a lower flow rate. Traditionally pool operators shoot for a certain amount of turnover to measure how much water is being treated. Even if you don’t focus on turnover rates, you can still think about what the water is doing during the hours of the day. Each hour, is it actively cleaning or sitting dormant?

A great benefit of lower flow is the ability to circulate the water for more hours each day. Because of the energy savings with modern pumps, you won’t see a huge energy spike from running the pump longer. In fact, you should actually save money compared to running a single-speed pump for less time.


When water is moving it is passing through the skimmer, capturing large debris. The water goes through the filter, grabbing tons of matter as we discussed above. Then in most pools, the water goes through some sort of sanitizer, usually chlorine. And maybe an added system like UV, Ozone or AOP. 

All of this water movement keeps the water clean and clear. And as the water moves in the pool, it also distributes the chlorine and the process continues. 

Worth noting: you may have experienced problems with some chlorinators at low flow. Most will not fill up correctly at low RPM settings. In this case, the tabs are not saturated and it is difficult to get chlorine in the water. But we solved this problem with Powerclean Tab VS. These are the only chlorinators designed to work at low flow rates without producing high back pressure.

By running the pump for more hours in the day, everything just works better. All of the systems that maintain the water require some sort of water movement. The longer the pump runs, the more the pool is kept clean—it’s that simple. So embrace the idea of running the pump more hours in the day!

More Power For Advanced Sanitizing

We’ve been discussing one advanced pool technology, the Variable Speed Pump. But there’s another significant tech that is growing every year. Yep, we’re talking about Advanced Sanitizers—products like Ultraviolet, Ozone and Advanced Oxidation Process.

Advanced sanitizers pack a punch that chlorine cannot match. The pool still needs chlorine as a residual in the water for many reasons. But adding a DEL system reduces chlorine use, kills things that can make you sick, and destroys nasty chloramines.

All advanced sanitizers work at a particular range of flow rates. They are specifically designed to meet certain contact time or venturi injection specifications—and all of these depend on flow rate. And great news:  in the majority of cases, lower flow is better.

For any system that uses ultraviolet, (like DEL UV-C or DEL AOP) as the flow decreases, contact time with the UV light increases. To a point, the lower the flow the better! 

With DEL Ozone systems as well, staying within a certain flow rate is key. High flow may produce more ozone (at first). Some UV-based ozone systems especially will use high flow as a way to increase ozone output. But as the flow increases, the ability of the water to absorb the extra ozone decreases. Essentially you are “wasting” that extra ozone and putting wear on the ozone system. So again it is not about more flow, it’s about the right flow.

While some manufacturers brag about their high flow metrics, the truth is cranking up the flow to the max isn’t doing you any favors. At the end of the day, it makes the product less effective. It’s ironic that right as VSPs are becoming a requirement, some manufacturers are bragging about their high sanitizer flow rates.

The importance of the flow rate is seen in guidelines like those from NSF. The sanitizing requirements for NSF specify a flow rate where the product is effective and meets the actual NSF standard. Even if a product has NSF certification, outside of the flow rate spec it is not sanitizing at the certified level. 

DEL brand products are perfect for the move to lower flow with the new DOE standards. Unlike some products that emphasize high flow rates to get the job done, our systems are designed around variable speed expectations.


Sure, change can be hard, but it turns out there are a ton of other benefits to variable speed pumps that run at a lower flow. Check out our Top 5 below.

1. Lower electrical costs from reduced pump speeds and stresses

2. Reduced noise levels due to quieter pumps – no more annoying the neighbors!

3. Longer pump life and less wear to the pool equipment 

4. Less stress on equipment and systems from constant max flow and pressure

5. More control over the “look” of water features

Hopefully, you already have, but now is the time to learn more about upcoming DOE pool pump changes. And the good news is this is a positive change. This is just another key to the Complete Modern Pool. Not only will homeowners save a ton on energy costs and equipment wear, but the whole system can operate better by running longer every day at a lower flow.

Learn more at c-m-p.com/modernpool.

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