Everything You Need To Know About Sand Filters
Filtering swimming pool water through a layer of fine sand is one of the oldest forms of filtration. That’s probably why sand filter systems are one of the most popular above ground swimming pool filter systems available today. Read on to learn more about how sand filters work, the pros and cons of sand filters, and other frequently asked questions.
How do sand filters work?
The process of sand filters is simple – the sand filter cleans the pool water with sand. The filtering sand sits in the filter tank and the swimming pool water flows through it. The dirt and debris in the water get trapped by the sand and stay behind while the rest of the cleaner water goes back to the swimming pool. As more pool water comes through the sand filter system, the more dirt and debris the sand will collect, so the filter becomes more efficient as it cleans.
What are the pros and cons of sand filters?
Let’s break down some of the pros and cons of this filter type:
Sand filter pros:
- Maintenance is easy since backwashing and rinsing the pool filter is a pretty basic process.
- Sand filters are usually the cheapest option available.
- They last quite a while (generally, 5-10 years).
Sand filter cons:
- Sand filters have a lower filtering ability than both DE and cartridge filters. Sand filters only remove dirt and debris down to 20-40 microns, allowing smaller particles to pass into the pool water.
- They’re the least energy-efficient option.
Typical pool filter vs. high-rate sand filter
The most modern style of sand filters being sold today, whose performance is beyond the best, is the high-rate sand filter. With this type of pool filter, the water enters the filter near the top of the filter tank. It is then dispersed evenly throughout the filter tank by the diffuser or baffle. This evens out the influent distribution of water to avert sand migration and channeling. The water is pushed, under pressure, toward the bottom of the filter. As the water travels from the diffuser toward the bottom of the filter it is forced through the sand filter media, where the dirt is strained from the water.
High-rate sand filters have a filter rate of 15 to 20 gallons per minute per square foot of filter area. They also work on the basis of depth filtration. The dirt removed from the water is not collected on top of the sand bed but is driven into the sand bed by the high velocity of the water. In a typical pool filter, the primary dirt load is confined to the top 2-4” of the sand bed. In a high-rate sand filter, the dirt is collected through the total depth of the sand bed.
How often do you need to change the sand in a sand filter for your pool?
The sand in the tank only needs to be changed every 5 years or so. This makes sand filter systems very easy to maintain because the tank only needs to be opened when the change needs to happen. Generally, you can tell the sand needs to be replaced when the filter needs to be backwashed more than normal. When replacing the sand, be careful not to crack any of the parts within the tank.
However, if the pool is sanitized with baquacil, the sand should be changed yearly to prevent system clogging.
Why is sand coming back into the pool?
Some swimming pool owners do notice that there is sand coming into the pool. If it’s not coming from the swimmers, the most reasonable excuse for this is the filter. This generally means that there is a broken piece in the filter that needs to be replaced. That can be solved by taking the sand out of the tank and finding that problem. This can also happen if there is too much sand in the tank.
Learn more about sand filter systems
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