Diatomaceous earth filters are expensive. Many municipalities strictly enforce DE disposal, and they aren’t the best fit for above-ground swimming pools. Cartridge filters only last a couple of years, and they can be tedious to clean. Is there an alternative to DE and cartridge filters?
If minimal maintenance and low cost are your top priorities, a sand filter fits both of your requirements. Sand filters work well with in-ground and above-ground swimming pools, particularly large ones. Although the sand remains effective longer than diatomaceous earth, you have the option of replacing the sand with materials that have a smaller volume and filtration rate.
These filters consist of a tank with high-quality sand at two-thirds capacity. On the top or the side of the tank, there is a multiport valve next to the pressure gauge, which gives you access to the filter’s multiple settings. As water flows into the tank, the rough edges of the sand catch the debris in the water.
No matter the ground level or size of your pool, you’ll find a great sand filter in our review list. We’ve compiled a list of the most solidly constructed sand filters available. In addition, we added a buyer’s guide, which explains how to size the filter, what each multiport setting means and how to backwash your sand filter.
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Best Pool Sand Filters
Pool Sand Filter Buying Guide
If you want to know more about how sand filters compare to diatomaceous earth and cartridge filters, check out our buyer’s guide, which also gives you the lowdown on the capabilities of silica sand and its alternatives. You’ll also find out how to size a sand filter according to your pool’s pump and volume.
Once you’ve found the right sand filter, our guide will tell you how to take care of it. In this guide, you’ll find instructions on how to replace the sand and backwash the filter. If you’re curious about your filter’s other settings, we’ve provided simple explanations that remove the mystery behind the multiport valve.
Filter Types: DE vs. Cartridge vs. Sand
Diatomaceous earth filters boast a 5-micron filtration rate, and you don’t need to break out chemicals to clean them. However, DE is pricey, and the filter’s grids only last 3 years. Most DE filters are incompatible with above-ground pools, and your city or county may have strict disposal rules for diatomaceous earth.
Cartridge filters can filter particles as small as 10 microns. You’ll use less water to clean them, and they work well with variable-speed pumps. Compared to sand filters, cartridge filters require more maintenance, and their lifespan is just as short as that of DE filters.
In terms of price and maintenance, sand filters are the winner. They also last much longer than DE and cartridge filters – often up to 7 years. However, there is one big downside to sand filters. They can only filter particles 20 microns and larger.
Characteristics of Sand and Its Alternatives
The type of sand used in sand filters is grade-20 silica sand. Many people prefer silica sand because it’s the cheapest medium, and it’s the easiest to maintain. Those who want a performance boost from their sand filter often opt for ZeoSand. Only half the amount of ZeoSand is needed, and it’s efficient at preventing chloramine buildup.
Made of recycled glass, crushed filter glass can trap particles as tiny as 2 microns. Filter glass also lasts much longer than silica sand, and you only need 20 percent the amount compared to silica. Pollyballs (polyester balls) have a 5-micron filtration rate. They’re resistant to chemical corrosion, and they can increase the pool’s flow rate by almost half.
Sizing a Sand Filter
There are two factors to take into account when choosing an appropriately sized sand filter – the pool’s pump and the pool’s capacity. When the size of the filter doesn’t match that of the pump, the system’s water flow will be hindered, and you could damage the filter.
For a 0.75 HP pump, you’ll need 2.7 square feet of sand. For a 2 HP pump, 5.8 square feet is appropriate. If the pool pump’s horsepower is rated at 1 or 1.5, you’ll need a filter that can hold 3.4 to 4.3 square feet’ worth of silica sand.
Sand filters are also sized by their flow rate of gallons-per-minute. The gallons per minute should meet or exceed that of the pool’s pump. At the very least, you’ll need 1 square foot of silica sand per 10,000 gallons of water. It’s perfectly fine to size the filter slightly bigger than the pump.
Cleaning a Sand Filter: Backwashing
The particles caught in between the sand granules gradually decrease the flow rate. Every 1 to 3 months, you’ll need to backwash your sand filter. You’ll know it’s time to take care of this routine maintenance task when the pressure gauge on the tank reads about 10 psi higher than normal.
First, turn off the pump and the heater. Then, open the drain outlet, set the sand filter’s valve to backwash and turn on the pump. Let the filter run for a few minutes. Once the water appears clear, turn off the pump and set the valve back to filter. Now, you can turn on the pump and heater.
Multiport Valve Settings
Slide valves only have two settings – filter and backwash. The filter setting is the one that keeps the water clean and circulating, so you’ll use this setting the most. Backwash reverses the water flow, allowing you to clean the filter itself. Multiport valves have more settings, including rinse, waste, closed, recirculate and winterize.
Rinse flushes the tank after you replace the sand. Waste bypasses the filter when you vacuum. Closed halts the water flow, making it easier to repair a malfunctioning pump. Recirculate also bypasses the pump, and you’d use this if your filter is leaking or cracked. Winterize is suitable for closing down the pool at the end of swim season.
Replacing the Sand in Your Filter
To get as many working years as possible from the sand in your filter, we recommend decalcifying the sand by using a cleaner once a year. Once you notice that pressure increases are happening faster than usual, a cleaner won’t cut it – You’ll need to replace the sand.
Pull the tank’s drain plug and remove the filter’s dome. Then, disconnect the pipe and detach the filter valve. Taking care not to break the filter’s laterals and standpipe, scoop or vacuum out the sand. Once you remove the sand, flip over the tank and rinse the laterals with a hose.
Now, you can add new sand. Make sure to pour in enough water to prevent the laterals from cracking, and never add more sand than the filter’s manufacturer recommends. Before reassembling the tank and valve, brush and lubricate the O-ring. If the O-ring is dry or warped, this is the perfect time to replace it.
Don’t forget to prep the filter for use. You’ll need to set the valve to rinse, then backwash, then back to rinse. If the tank has a slide valve, simply run a backwash cycle. Always turn off the pump when you change valve settings. When you’re done prepping the filter, you can set the valve to filter.
What Are Microns?
Microns, also called micrometers, are a form of measurement. One micron equals one-millionth of 1 meter. Pool filter manufacturers use the micron measurement to describe the width of particles that their filters can trap. To help you visualize the size of 1 micron, a single hair strand measures approximately 50 microns in width.
How Do I Know When It’s Time to Replace My Sand Filter Tank?
While you do have to replace the sand once the edges become smooth and the granules can no longer trap particles, you’ll eventually need to get a new tan. There are several signs that indicate a tank has surpassed its useful life. The first sign you’ll probably notice is an odd pump noise coupled with a leaking port.
Sometimes, you’ll need to replace the tank for other reasons besides wear and tear. For instance, if the sand inside is relatively new but you still find yourself backwashing the filter more than once a month, the filter may be undersized for your swimming pool.
Why Do I Have to Sanitize My Pool If I Have a Sand Filter?
As you’ve read, silica sand has a filtration rate of 20 microns. However, many particles are much smaller. Bacteria ranges from 0.3 to 2 microns wide, and algae can be as small as 8 microns. Therefore, the filter is limited as to the contaminants it can catch. This means you must sanitize the water to ensure it stays hygienic.
Pool Sand Filters: Recap
Every swimming pool needs a filter. As far as filter media choices, you have three – diatomaceous earth, cartridges and sand. While each type of filter has its own set of pros and cons, sand is the media of choice for those who want to save money and spend less time on filter maintenance.
If you decide to go the sand filter route, you don’t necessarily have to use grade-20 silica sand. There are fill materials with smaller filtration rates and larger surface areas, such as ZeoSand, filter glass and Pollyballs. While sand alternatives offer many benefits, none of them are as inexpensive as traditional silica sand.
When browsing for a sand filter, your choice should be steered by the volume of water in your swimming pool and the horsepower of your pool’s pump. The gallons per minute of the filter can be a little bit more than the pump’s; however, you should never undersize the filter.
Once your sand filter is in place, familiarize yourself with the valve’s settings – multiport valves have more settings than slide valves. Make sure you replace the sand once per 5 to 7 years or longer for some sand alternatives, and backwash the filter every 1 to 3 months.