Is there a big difference between filters for above ground pools and in ground pools? They both filter the water, right? Also, the manufacturer’s specs tell me this filter can filter up to a 20,000 gallon pool. So why should you pay more than double the price? The short answer is yes, but let’s not be stingy or stupid.
Those are typical and reasonable questions that many pool owners ask. Let’s look at some of the main differences between filters for above ground pools and in ground pools. But first we will see the similarities.
The similarities between inground and above ground pool filters are quite simple. The first similarity is that there are 3 types of pool filters: sand, diatomaceous earth (DE), and cartridge. The second similarity is that they work essentially the same way: a pump draws water from the pool through the skimmer, then the water is pumped through the filter tank and its media (sand, DE, or cartridge) and back into the pool. clean and filtered. .
The differences have to do with the plumbing or piping of the pool, the flow needed, and finally the size. Let’s discuss them in order.
Pool plumbing. The biggest difference may seem like the size and volume of the pool. But really, it’s more of a function of the pool’s plumbing. Most above ground pools have their filter system right next to the pool. Also, the filter and the pump and motor are usually located below the water level. In other words, the filter system is usually on the ground with the skimmer hose feeding directly to the pump and the filtered water going back into the pool’s return jet – gravity feed. Most above ground pools have no more than 6 to 9 feet (about 2 to 3 meters) of hose on each side, a total of 12 to 18 feet.
Inground pools, on the other hand, can and do have many more feet of tubing and plumbing. On top of that, there are usually multiple skimmers or other suction lines, sometimes working together, sometimes not. Then there are multiple return fittings or “eyeballs” or jets. Here’s an example, my pool (only about 16,000 gallons) has a skimmer, bottom suction, and 2 return fittings. Each wall fixture has its own plumbing line. Even though the filter is only 15 feet from the pool, let’s see how many feet of tubing there are for each line. The skimmer and bottom suction are relatively close to each other, so each uses about the same amount of tubing: about 40 feet each line or a total of 80 feet going to the pump. Return fittings are on opposite sides of the pool. One return line is about 30 feet from the filter, the other is about 50 feet, another 80 feet. My pump and motor have to pull and push water a total of over 160 feet or TEN times the distance of an average above ground pool. Also, we have not mentioned the heater, valves, elbows and other accessories used in in-ground pools.
necessary flow.Understanding flow is the “great mystery” of the pool industry. Very few people practice it well. Simply put, FLOW is putting the correct amount of water through the system to properly filter the water. It’s not just about horsepower. In fact, most pool systems run on too much power. And that is a waste of energy and money. Think of it this way: All pipes or hoses (depending on their size or diameter) can only handle a certain amount of water flow, say that’s 100 gallons per minute (gpm), for example. You or the pool manager decide a new pump is needed. “Let’s use something a little bigger that will give you ‘better’ suction,” he says. Now installed a pump that pumps 125 gpm – great! Not so fast! Your pipes can only handle 100 gpm. Do you have better suction? Maybe. Are you using more power to run the larger pump? Definitely. Approximately 25% more energy. Not only that, but the filter doesn’t seem to filter as well as it used to. This is because the water is being pushed through the media too quickly (especially in the case of sand filters); the filtration system has to run longer because dirt cannot be trapped as easily.
But that’s only part of the flow discussion. The other part is something called “head”. The head is the height at which the pump must pull or push the water up. Most inground pools have their filters above the water level. Sometimes within one or two feet (less than 1 meter). Sometimes it can be 10 to 15 feet. The pump has to take all the water out of the pool 15 feet to the filter. Think of it this way: Is it easier to hold a glass of water above your head and pour it into your mouth, or to use a straw to sip (suck) it? In addition, there are solar heating panels (often installed on the roof of the house or in the pool shed) and fountains or other sources of water.
Size. Finally we come to size. Pool size. Filter size. All is important. Can an above ground filter system filter 20,000 gallons of pool water? Yes. But is an above ground filter system capable of properly pushing water through 100+ feet of tubing and creating enough circulation in the pool to push water down 6 or 8 feet deep and back up again? go up? Or how about doing all of that plus carrying the water 25 to 30 feet in various directions? Inground pumps are made to do all of that by pushing and pulling water. Surface bombs can’t.
How about the filter size? Inground pools typically hold 20,000 to 40,000 gallons of water. All that water needs to be filtered 2-3 times a day for best performance (see our Proper Circulation ezine article: “Circulation: The First Key to Good Pool Care” for more information). A larger filter is needed for the larger volume of water.
As a necessary aside, larger above ground pools (27 foot round and larger, and 18 x 33 oval and larger) should consider using a properly sized inground filter system. After the first season, many large above ground pools experience water quality problems due to inadequate filtration systems. Unfortunately, these pools are “hampered” by the problem of having only one skimmer and one return cut-off. Ask your local pool professional to set up your system correctly. Will it cost more initially? Yes, but you will be much more satisfied in the years to come.