While a sand filter can be used with your saltwater pool, it isn’t your only option. Sand filters are the original form of pool filter and they are very commonly used by saltwater pool owners for both commercial and home use. Sand filters provide the lowest level of filtration however when compared to the other two options available. They do tend to be the cheapest though.
Cartridge filters are the second type of pool filter that provide the next level of filtration, better than that offered by sand filters. The third and final option is the Diatomaceous Earth (D.E) filter which offers the highest level of filtration albeit with several important provisos.
Can I Use A Sand Filter With Saltwater Pool System?
Yes, you can use a sand filter with saltwater pools systems but as mentioned, two other options exist that you might consider. It should be noted that sand filters are generally the cheapest filter option to purchase.
Below we compare all three filter options and their ability to remove particles that are measured in micrometers. NOTE: 1 micron = one-millionth of a meter. For comparison a white blood cell is about 25 microns.
Sand Filter
As the name suggests, a sand filter uses a special type of sand to filter out particles before returning water to the pool. A sand filter typically filters out particles as small as 10-20 microns which is the worst performing of the three filter options.
A 50 lbs bag of pool filter sand retails for about $25-$50. There are plenty of options and quality levels to choose from. A typical sand filter as we’ll see below may hold 50 lbs – 700 lbs of sand depending on the size. So a reasonably sized pool filter with 200 lbs of sand capacity would cost about $100-$200 to fill up.
Sand filters need to be backwashed to rinse and wash the dirt out as the sand holds all the contaminants that it has pulled from the water. This increases the work involved and also your water usage as your pool will need to be topped up when water is drained through the filter to rinse it. Typically a sand filter will be backwashed when the pressure gauge reaches 8-10 pounds per square inch (psi) or about once per week. A waste valve is opened and water is pumped out for several minutes or until the water is clear. Water then needs to be added back to the pool which can also impact water chemistry.
Sand typically has to be replaced every 5-7 years and depends on the size of the pool, amount of usage, how dirty it gets and how well you take care of the filter.
Cartridge Filter
A cartridge filter system uses 2-4 round pleated drums which sit inside the outer unit and filter contaminants out of the pool. A good cartridge filter can remove particles as small as 5-10 microns so it is a better filtering option than sand if filtering smaller particles out of the water is important to you. Cartridge filters collect and hold onto debris and contaminants so they need to be rinsed from time to time to clean them out, rather than backwashing. A decent set of cartridges will last several pool seasons, perhaps 3 years on average.
Cartridge filters can get clogged with certain contaminants that impair its ability to work properly. Algae is particularly hard on them and cartridges may need to be rinsed after cleaning a pool of algae, perhaps more than once. In my experience, I don’t have to rinse cartridges more than 1-2 times per pool season unless an algae outbreak occurs which requires more washing. A cartridge can also have its life extended and realize improved efficiency through use of a filter cleaner which removes oils and other contaminants that simple rinsing can’t.
D.E. Filter
A D.E. filter is the newest type of pool filter and while it offers the best filtration of particles as small as 2-5 microns, it also tends to be the most expensive option and requires both rinsing and backwashing. So it also requires the most maintenance.
Also, the diatomaceous earth used in the filter needs to be topped up every backwashing and since D.E. is considered a class 3 carcinogen, care need to be taken when working with it.
Like with the sand filter, a waste valve is opened for the backwash and water is pumped out until the water runs clear. Also, the filter grid need to be washed and rinsed at least once per year with a degreaser and possibly an acid bath to properly clean them.
Choosing A Sand Filter
Before you choose a sand filter you need to consider the following:
Inground/Above ground pools
Some sand filters can operate with inground pools, above ground pools or with both. Ensure you pick the right one for your pool type.
Your pool size
Very important: Get a filter size that can serve your pool volume. What is the volume of your pool in gallons or liters? Many large sand filter manufacturers like Hayward and Pentair produce brands with multiple options that range in size depending on how much water you need to filter. Some filter products refer to the size in gallons or liters that it can filter. Some refer to a filtration size in square inches of filter area. You need about 1 square inch of filtration for every 1,000 gallons of water so an 18,000 gallon pool needs an 18-inch sand filter tank, a 23,000 gallon pool needs a 23-inch sand filter tank and so on.
Gallons per hour of filtration
Also very important: Pick a filter that is capable of filtering an amount of water every hour of operation that suits your pool size and the amount of time you will run your pump. So if you have a pool with 20,000 gallons and will run your pump 10 hours per day, you need a filter that can filter 2,000 gallons per day (20,000 gallons / 10 hours). A Hayward S200 sand filter (for example) is rated to filter 0-50 gallons per minute, or 0-3,000 gallons per hour. So this filter could work for this 20,000 gallon pool with a pump being run 10 hours per day.
NOTE: Be careful as some filters are capacity rated in gallons per minute (GPM) and others are gallons per hour (GPH).
Your pump and piping
Your pool pump capacity and piping size also matter because even if your filter is capable of filtering X gallons per hour, your pump and piping need to actually be capable of doing it, too. Pool pumps and piping come in different sizes as larger options are available for larger pools requiring greater water flow. Check out the pool pump sizing calculator from EcoPump if you’d like a recommendation emailed to you. You can also check out the pool size sizing chart from Pool Plaza if you’d like an idea right away.
Your budget
How much do you want to spend? Sand filters range in price depending on the brand, manufacturer and filtration size. In some cases you might be in a certain price point regardless due to your large pool water volume. The larger your pool, the more filtration ability you need which means a larger filter capacity is required.
Sand filters are easily found for $200-$800 in different sizes and from different manufacturers.
Where do you live?
If you live in a freezing climate like I do, you might check to see if your chosen filter is easily removed to bring inside during a harsh winter. Having said that, this would also potentially entail replacing sand every winter because you’ll have a hard time dragging an average filter with 200 lbs + of sand indoors for winter and outside again in the spring.
Popular Sand Filters To Consider
Here are a list of popular pool sand filters from some of the major manufacturers:
Hayward S270T Pro Series 27-Inch Pool Sand Filter (holds 350 lbs of sand)
Hayward Pro Series Sand 30 inch Filter (holds 200-700 lbs of sand depending on size)
Hayward S200 Series (1-23 Sq Feet filtration area, holds 200 lbs of sand)
Hayward W3S200 Series (1-23 Sq Feet filtration area, holds 200 lbs of sand)
Pentair Tagelus Top Mount Fiberglass Sand Pool Filter (175-600 lbs of sand depending on size)
Pentair Cristal-Flo II Top-Mount Filters (100-350 lbs of sand depending on size)
Pentair Sand Dollar Top Mount Pool Filter (100-350 lbs of sand depending on size)
Pentair Sand Dollar Pool Filter with ClearPro Technology (350 lbs of sand depending on size)
SUNCOO Pro 2450GPH Sand Filter Pump (up to 10,000 gallons, holds 45lbs of sand)
Conclusion
- A sand filter is the oldest form of pool filter and while many brands are still widely available to use, it doesn’t offer the same level of filtration as a cartridge filter or the superior D.E. filter.
- Sand filters do also require backwashing which involves rinsing water out every week to clean the filter when increased work, water usage and can put water chemistry out of whack.
- So while you can use a sand filter for your salt water pool and it will probably be the cheapest option overall, it does involve more work and offers the lowest level of filtration.
- Check out my other post called Best Salt Water Filter For Pools for a more detailed look at all three pool filter options and why you might consider one over the other.