Out of all the components that make up a pool’s circulation system, the pump consumes the most energy. You can calculate a filter cycle to reduce the time it runs and conserve energy. However, you risk under-calculating the cycle and not giving the system a chance to filter all the debris and disperse all the cleaning chemicals.
To get an accurate flow rate, you need a flow meter. Simple yet effective, a flow meter tells you the rate of the water’s movement through the pool’s circulation system. You can use this measurement to set a timer and detect leaks/failures in the system. Flow meters also help you maintain a sand filter.
Flow meters are sized to the diameter of the system’s pipes. They come in a variety of styles from traditional analog types with a pilot tube to advanced models that utilize ultrasonic technology. There are even flow meters that act as a check valve, preventing the backflow of water that otherwise occurs when you turn off the pump.
Since there are so many options from which to choose, we reviewed the most reliable flow meters we could find. We also added a buyer’s guide, so you can make sure the flow meter you get is compatible with your swimming pool. This guide also has other helpful information, including how to install, maintain and repair a flow meter.
Best Pool Flow Meters
Pool Flow Meter Buying Guide
Before you buy, there are several questions you must ask yourself. Do I want a basic flow meter with a floating bobbin or one with a digital readout? What kind of pipes are used for my pool’s plumbing system? What is the diameter of those pipes?
We will tell you how to determine whether the flow meter you’re interested in buying is built to last. After you pick a flow meter, you have to learn how to install it and maintain it – installation and care instructions are also included in our buyer’s guide.
Types of Pool Flow Meters
The most common type of pool flow meter is one that has a floating bobbin contained inside a pilot tube. These analog flow meters can be positioned horizontally or vertically, and they’re installed by drilling a small hole into the swimming pool’s existing plumbing. Usually, two clamps are applied to provide more stability.
Like analog flow meters, digital ones can be installed on a saddle mount without cutting the pool’s pipes; however, digital meters display the flow rate on an LCD screen. While digital flow meters are highly accurate, they do require electricity or a battery for their power source. Battery-powered digital meters are often portable.
Magnetic and ultrasonic flow meters are two other options. Typically used for commercial pools, both varieties are also great for residential swimming pools as they are compatible with most pipe materials. Magnetic flow meters use a magnetic field to send a voltage signal proportional to the water’s flow rate while ultrasonic models rely on sound waves.
Finally, there are models that are part flow meter, part check valve. You can install these combo flow meters horizontally, vertically, upside-down and next to pipe elbows. With a dual-purpose flow meter, you can not only check the water’s flow rate but also prevent water backflows, which would otherwise occur when you shut off the pump.
High-Quality Flow Meter Characteristics
You don’t want to be stuck with a flow meter that you’ll have to replace a few years down the road or one that gives inaccurate readings. Those with a CNC-machined body are among the most durable and accurate. Whether a dual-purpose or traditional analog flow meter, Lexan is always preferable compared to acrylic.
Combo flow meters should have an anti-corrosive flapper seal, pivot pin and spring. For analog flow meters, a stainless-steel bobbin that doesn’t stick or bounce provides accuracy year after year. The meter’s markings should be dark and easily readable and stainless-steel clamps are recommended over aluminum.
Sizing a Flow Meter
There are three must-consider aspects for sizing and selecting a flow meter. All aspects are determined by the pool’s plumbing system, specifically the pipe’s diameter, material and thickness. The pipe’s diameter needs to match the meter’s rating. For example, only a 2-inch flow meter fits a 2-inch-wide pipe.
You’ll also need to base your decision on the pipe’s material. Some flow meters work with PVC while others are only made to use with copper. Then, there is the pipe’s thickness. PVC pipes are either scheduled as 40 or 80. Eighty is thicker and can handle high-pressure applications.
Installing a Flow Meter
All flow meters come with different installation instructions, which will vary depending on the pool’s pipes. In general, the meter should be placed on the return line after all system components except a chemical feeder, and you need to leave five times the pipe’s diameter before the meter and two times the diameter after it.
To install an analog flow meter, you must first turn off the pump’s power and open the filter’s relief valve. After you mark the meter’s location on the pipe, drill a hole in the center of your two markings. We recommend making a pilot hole first, so the drill bit won’t slip when you drill the actual hole.
Once the hole is drilled into the pipe, remove the burrs (rough spots) around the hole with a deburring tool. Then, you can cover it with the gasket and insert the meter’s pilot into the hole. Make sure you position the meter to face the water’s flow direction. Most flow meters have a guide arrow to help you.
Finally, you can place the clamps. Put one clamp on each side of the flow meter. Tighten the clamps slowly while keeping the meter from shifting out of place. Next, restore power to the pump and close the relief valve as soon as you see water coming out of it.
Maintaining Your Flow Meter
Periodically, you’ll need to flush out sediment to keep the bobbin floating freely. Out of all meter types, traditional analogs require maintenance most frequently. Start by unscrewing the nuts at the top and bottom of the pilot tube, so you can remove the tube. Then, flip the meter upside-down and shake it until the float moves to the top.
Inside the pilot tube, there’s a guide support and a wire. You’ll need to pull out both along with the bobbin to rinse the interior with soapy water or diluted muriatic acid. Once you clean the inside of the tube, you can then reassemble the flow meter, ensuring the float’s pointed end faces downward and the O-ring is debris-free.
Repairing Your Flow Meter
Despite proper installation and maintenance, you may eventually be faced with a small leak. Thankfully, leaks are easy to fix with silicone lubricant, which creates a water-tight seal while providing pliability for future maintenance.
First, turn off the pump and open the filter’s pressure-relief valve. Then, loosen the clamps, so you can gently pull off the gasket and flow meter. If the gasket is worn, replace it. If not, add silicone lubricant to the gasket and around the hole in the pipe. After applying the lube, place the gasket back over the hole.
To cover every possible origination point of the leak, apply some lubricant on the pilot’s insert. At this point, you can put the flow meter back into the hole and secure the clamps. Close the air relief valve and turn on the pool’s pump. Make sure there is no water dripping from the flow meter before you call it a day.
How Can a Flow Meter Help Me Maintain My Sand Filter?
Sand filters are affordable and easy to use. Every 1 to 3 months, you will need to clean your sand filter. The exact frequency depends on the filter’s size and debris load. If you have a flow meter installed on your pool’s plumbing system, you can use both to make sure you stay on track with filter maintenance.
Look at the pressure gauge and note its readout. Then, do the same with the flow meter. If you notice a flow increase of 10 psi or greater between the gauge and meter, it’s time to clean out your sand filter.
How Do I Use My Flow Meter to Set a Pump Timer?
By using your flow meter to set a timer for your pump, you can shave off hundreds of dollars from your electricity bill. Although some people rely on the gallons per minute supplied in the pump’s specs, this measurement doesn’t account for the total dynamic head (TDH), which consists of the multitude of variables that skew that number.
To set the timer for a length of time that maximizes your energy savings while efficiently filtering your pool, you’ll need to calculate the volume of the pool. For square and rectangular pools, multiply the length, width, average depth and 7.5. For circular pools, multiply 3.14 by the squared radius, average depth and 7.5.
If you’re unsure of your swimming pool’s average depth, here’s an easy way to find it. Take a telescopic pole and dip it into the shallow end until the pole reaches the bottom. Mark the pole at the waterline and do the same in the deep end. Add the two lengths together and divide the number by two.
Once you have measured the pool’s volume, you need to divide the volume by the turnover rate you want. We recommend 6 or 8 hours. Finally, divide that number by 60 to find the gallons per minute. One cycle is okay for days when nobody uses the pool, but two times may be necessary for heavy-use days.
How Do I Read an Analog Flow Meter?
Depending on your viewpoint, the bobbin can appear to lie on a different marking than it actually does. To get an accurate reading, crouch until you’re eye-level with the bobbin. Look at the top edge of the bobbin – The marking that corresponds to the bobbin’s edge is the true flow rate.
Pool Flow Meters: Recap
There are a lot of tasks involved in keeping a swimming pool up and running. Pools heavily rely on their pump and filter to stay clean. If you don’t run the pump often enough, the water will become unhygienic. Conversely, if you run it too often, you’re wasting electricity. Plus, sand filters can fail if not cleaned promptly.
Flow meters solve several problems. They measure an accurate flow rate, so you can set the pump to run for a filtration-efficient, energy-smart amount of time. They also help you keep track of when to clean your sand filter (should you have one).
You have plenty of flow meters from which to choose. There are simple analog meters and ones with a digital display. You can go the public-pool route and get a magnetic or ultrasonic flow meter. If you want to replace your check valve with one that also provides the water’s flow rate, there are meters that do both.
When buying a pool flow meter, durable construction and accurate readouts should be your main concerns. However, you also need to make sure the flow meter will work with your pool’s plumbing. Check the pipe’s diameter, material and thickness to ensure the flow meter’s compatibility.