Swimming Pool Flow Meters 101: Types, How to Install, Why You Should Use One, and More

Like most homeowners, you want to find ways to save money on the maintenance and upkeep of your home. When it comes to your swimming pool, a little bit of know-how can go a long way toward keeping your money in the bank.

A swimming pool flow meter is one piece of equipment that can keep you alert to issues with your pool and its plumbing and mechanical systems. The flow meter is a device that tells you how quickly the water in your swimming pool is circulating through its plumbing system.

Understanding how well the water is circulating is essential, and a flow meter is much more reliable than waving your hand past one of the returns to gauge the force of the water coming out of it.


Main Takeaways

  • There are three types of pool flow meters: analog, digital, and inline/integrated
  • The type of pool flow meter you buy will also depend on the size of your pool pipe size
  • Your swimming pool should have a flow rate of 30-45 GPM
  • Make sure your swimming pool is chemically balanced to avoid buildup in your pool flow meter

What Is a Pool Flow Meter?

A pool flow meter is a device that tells you the speed of the water circulating through your swimming pool’s system. I refer to the plumbing and mechanical aspects of a pool collectively as a system.

Why Should You Use a Pool Flow Meter?

The significant benefit of installing a pool flow meter on your pool is that, at a glance, you can see if something is affecting the circulation of your pool water. Good circulation is essential for a few reasons.

First, your pool water should routinely and thoroughly cycle through the filtration system. This circulation is how you ensure that the filter media mechanically filters all your water.

Larger debris will end up in your skimmer baskets, and your filter will catch smaller debris. If you have poor circulation, you will have to run your filter for much longer to complete filtration.

Second, good circulation will ensure that your pool’s water receives adequate sanitization. The sanitizing chemicals you use need to be well-distributed to kill any contaminants.

It doesn’t matter if you have a saltwater chlorine generator, liquid or tablet chlorinator, ozonator, or UV sanitizer. Good circulation helps expose all of the water in your pool to your sanitizing agents, ensuring that all water is treated adequately.

Finally, good circulation is essential for maintaining the temperature of your water. Even without a heating system, the sun’s energy will warm the surface water of your pool.

Without adequate circulation, the colder water on the bottom might never mix with the warmer air on top, making swimmers uncomfortable. Furthermore, if you have installed a pool heating system, you want to ensure that it heats all of the water and not just some of it (for more on heaters, read my guides on the best pool heaters and best solar pool heaters).

Different Types of Pool Flow Meters

Flow meters come in three different varieties: analog, digital, or inline/integrated.

Analog

The analog meter is the simplest and usually the easiest to install. You will need to drill a small hole in the top of your plumbing. Your meter will fasten over the hole with a saddle or clamp, and its float valve will pressurize from the force of the water going through the system.

You can determine the flow rate by looking at the gauge’s indicator.

An analog flow meter looks like an old mercury thermometer. They are relatively inexpensive, usually costing well under a hundred bucks for models up to 2″ pipe diameter.

Here is an example of a good analog pool flow meter from Blue-White. This model is for 2″ pipes, so make sure to choose a different option that fits your setup. Flow Vis also makes good analog meters.

If you have a huge pool, you may have larger diameter pipes. Still, even a 4″ flow meter isn’t much more expensive. Most DIYers can install one pretty quickly.

Digital

Digital flow meters operate similarly to an analog model. They tend to be much more accurate than their analog counterparts, and they aren’t that much more expensive. Blue-White makes good digital flow meters.

They require power, so you will need electrical access. Some units will need to be hardwired into your system, especially if they interact with your chemical feeders.

Inline or Integrated

Inline or integrated flow meters are a section of a pipe with a flow meter installed inside it. A typical model features an inlet and outlet with bulb-shaped housing in between.

If needed, chop out a section of pipe and install this flow meter in the gap using PVC glue and some new PVC pipe. The flow meter gauge will tell you the flow rate of the water traveling through it.

Other Considerations When Purchasing a Pool Flow Meter

To choose the proper flow meter for your pool, you need to know your pipe size and what it’s made of. Most swimming pools feature PVC plumbing, so the material will be less of an issue to figure out than the size.

The pipe size matters because it is part of the equation determining your flow rate. Your pool pump sucks the water out of your pool, pulling it into the skimmer. Then it travels through your pipes and into the pump. The pump pushes the water out and into the filter.

The water in the filter is pressurized and forced through your filter media. Most filters have a little gauge that shows the pressure reading, so you can determine when it is dirty and needs cleaning.

Finally, the filtered water passes through any ‘downstream’ equipment like heaters or sanitizers and returns to your pool. If your pipes are smaller, it will force the water to move faster. So there are flow meters optimized for different-sized pipes.

There are also models specified for the orientation of the pipes you are mounting them to. For example, if your pipe run is vertical, you need a sensor that works vertically. And you would want a sensor that works horizontally for a horizontal pipe.

How to Read a Pool Flow Meter

Reading a pool flow meter is usually just glancing at the gauge or display. Some very rare high-end systems might have a remote display that you can access from a panel inside your home or even on your smartphone or computer.

You will likely need to go to where the flow meter is installed and look at what it says. A digital meter will show you a number.

The much more common inline or analog models have a simple gauge with an indicator bar that shows your water flow rate, usually in gallons per minute (GPM).

Most swimming pools should be in the 30 to 45 GPM range, but it varies by size and design. To calculate the minimum flow your water should be moving for an 8-hour water turnover rate (3 complete turnovers a day), use the following formula:

Pool Volume x 3 / 24 / 60 = Minimum Flow (GPM)

Similarly, for a 6-hour water turnover rate (4 complete turnovers a day), use:

Pool Volume x 4 / 24 / 60 = Minimum Flow (GPM)

How to Install a Pool Flow Meter

The exact steps for installation vary by the type of sensor you are installing.

Analog Flow Meter Installation

Step 1: Carefully measure the insert on the end of the meter. Follow the manufacturer’s instructions to use the right-size bit for your drill.

Step 2: Drill a hole into your pipe.

Step 3: Use the clamp on the meter to hold it in place.

Digital Flow Meter Installation

Follow the same steps as the analog flow meter for a digital flow meter.

As an additional step, it will need to be connected to power and possibly hardwired to your other pool systems, depending on the model.

Inline Flow Meter Installation

Step 1: Cut out a section of the pipe large enough to accommodate the installation.

Step 2: Using additional slip fittings or unions, rebuild the run of the pipe from one cut to the new flow meter and out the other side.

Where Should Your Pool Flow Meter Be Located?

There are two things to consider when installing a pool flow meter. The first is that it should be someplace easily accessible. If you need to take a reading, you don’t want to crawl on the floor or stand on your head. Put it somewhere on the top of a pipe that you can easily see.

Second, make sure the meter is located someplace after your filter. If you install your flow meter in an area of the plumbing before the water is filtered, it can become clogged with debris, making it inoperable.

How to Troubleshoot a Pool Flow Meter

The most likely cause of a problem with a flow meter is that it is clogged with debris or stuck in one position. To remove a clog, you need to access the flow meter.

An inline model will have a series of screws holding the lid. Simply remove the screws, and inspect the float, flapper, and housing for any debris.

Make sure the float moves freely. If this is a brand new installation, ensure that you installed the meter in the right direction. There is usually an arrow to indicate which way the water needs to move through the flow meter.

An analog or digital flow meter will need to be unscrewed or twisted out of the pipe for inspection and cleaning. Remove the clamp, pop it out of the pipe, and look for debris clogging the float.

A digital flow meter might have a filter screen, as you might find on a washing machine hose. Make sure that the screen is clean as well.

Sometimes, your pool flow meter can also be affected by buildup, scale, or mineral deposits from your pool water. The best way to prevent this is to ensure that your pool water is always well balanced.

A swimming pool can often feel like a big, open-air chemistry experiment. But by keeping your pH, total calcium hardness, and total alkalinity in the appropriate range, you can minimize the risk of buildup from the dissolved solids in your pool water affecting your equipment, including your pool flow meter.

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Bottom Line

A pool flow meter is a good tool for a swimming pool owner. By monitoring it, you will make yourself aware of any issues affecting your swimming pool’s circulation.

For instance, if you think the water is moving slower than usual, you might assume your filter is dirty. So you will backwash or clean the grids and guess everything is OK. But with a flow meter, you don’t have to guess.

With it, you will see if cleaning the filter media has fixed your flow issue. If your flow rate doesn’t return to normal, take the following steps: check your pump’s hair and lint basket for debris, make sure there isn’t any obstruction in your skimmers, and double-check your valve positions.

If you have a multi-speed pump, a flow meter can also help you fine-tune the operation of your system to save energy and money. With the price of chlorine skyrocketing, every bit we save counts! If you don’t have this type of pump, head to my recommendations for the best energy-efficient pool pump.

Have questions? Drop me a message, and I’ll be happy to help.

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