Is there a big difference between filters for above-ground pools and in-ground pools? They both filter water, right? Also, the manufacturer’s specifications tell me that this filter can filter a pool up to 20,000 gallons. So why should you pay more than double the price? The short answer is yes, but let’s not be wise 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 in-ground and overhead pool filters are pretty 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 medium (sand, DE, or cartridge) and back into the pool. clean and filtered. .
The differences have to do with the plumbing or plumbing of the pool, the required flow and finally the size. Let’s discuss them in order.
Pool plumbing. The biggest difference may appear to be pool size and gallonage. But really, it’s more of a pool plumbing function. Most above ground pools have their filtration system right next to the pool. Also, the filter, pump and motor are generally 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 returning to 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 in tandem, 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, lower suction, and 2 return fittings. Each wall fixture has its own plumb line. Although 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 per line or a total of 80 feet at the pump. Return fittings are on opposite sides of the pool. One return line is about 30 feet from the filter, the other about 50 feet, another 80 feet. My pump and motor have to pull and push water a total of more than 160 feet or TEN times the distance of an average swimming pool above ground. Also, we have not mentioned heaters, valves, elbows and other accessories used in inground pools.
Necessary flow.Understanding flow is the “great mystery” of the swimming pool industry. Very few people do 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 (based on their size or diameter) can only handle a certain amount of water flow, let’s say it’s 100 gallons per minute (gpm), for example. You or the pool manager decide that a new pump is needed. “Let’s use something a little bigger that will give you better suction,” he says. There is now a pump installed that pumps out 125 gpm – great! Not so fast! Your pipes can only handle 100 gpm. Does it have better suction? Maybe. Are you using more energy 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 pushed through the medium too fast (especially in the case of sand filters) – the filter 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 of the pump to pull or push the water. Most inground pools have their filters above the water level. Sometimes within a foot or two (less than 1 meter). Sometimes it can be 10-15 feet. The pump has to bring all the pool water 15 feet to the filter. Think of it this way: is it easier to hold a glass of water over your head and pour it into your mouth or use a straw to sip (suck on) 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 water features.
Size. Finally we come to size. Pool size. Filter size. All is important. Can an above-ground filtration system filter 20,000 gallons of pool water? Yes. But is an above ground filtration system capable of properly pushing the water through 100+ feet of pipe and creating enough circulation in the pool to push the water down 6 or 8 feet deep and back again? ? Or how about doing all of that in addition to taking the water 25 to 30 feet in various directions? Buried pumps are made to do all that pushing and pulling of water. Aerial bombs can’t.
How about the size of the filter? Inground pools typically hold between 20,000 and 40,000 gallons of water. All that water should be filtered 2-3 times a day for the best performance (see our ezine article on proper circulation: “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 addition, larger above ground pools (27 ’round and larger, and 18 x 33 oval and larger) should consider using an appropriately sized buried 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 configure your system correctly. Will it cost more initially? Yes, but you will be much more satisfied in the years to come.