It's the simplest of the pool filter media, a material with which anyone who's ever walked on a beach is familiar. And generally speaking, the granular medium just lies there filtering out gunk, but there are still a few sand pitfalls to watch out for and a trick or two you can use to boost filter performance. With that in mind, we offer these tips from experts across the country to help keep sand filters working at peak efficiency and your customer's pool water clear and clean.

Calcification — Accumulation And Remediation

In areas that have very hard water and high calcium hardness levels, calcium buildup can become a real problem in the sand bed. In Steve White's Boston-area service district, high-mineral-content water is a common problem:

"Our area uses primarily sand filters," he says, "for both residential and commercial pools. We find that we often have too much calcium build up in the pool water which leads to calcification in the filters, especially in pools where Cal-Hypo is used."

Acid cleaners can tackle a crusty calcium buildup in the filter, but if the water is hard enough and the problem has been ignored too long, the sand bed can look like it could be used as a concrete footing for a major backyard construction project. In that case, it will have to be removed — an enjoyable task.

A Little Clarification

AQUA Filter Panel:

Dan Lenz, All Seasons Pools & Spas, Orland Park, Ill.

John Bokor, regional sales manager, ProTeam, Mich.

Steve White, owner and president of Underwater Pool Masters, West Boylston, Mass.

Terry Arko, recreational product specialist for SeaKlear Pool and Spa Products, Bothell, Wash.

Sand filters are renown for their robustness as filter equipment, but when it comes to extracting the tiny bits of debris that can cause water to lose its sparkling brilliance, they may need a hand. Service techs looking to get that crystalline transparency in the water — especially water that will be lit up at night, when every little floater draws attention — try adding some dry clarifier to help remove fine particulate. The clarifier coats the sand bed, filling in any nooks and crannies in the media, and is then simply washed out of the filter during the backwash without leaving any residual, says John Bokor, regional sales manager for ProTeam, a brand of Haviland Pool and Spa Products, Grand Rapids, Mich.

"Using a dry clarifier increases filter efficiency by penetrating the sand with a polymer formula and restores water quality after heavy rain and/or bather loads," Bokor says. "These products attract small particles and capture them in the filter."

Terry Arko, water treatment specialist with NC Brands/SeaKlear, agrees. "Using a clarifier product can be an invaluable aid for sand filtration. Depending on the product being used, it can enhance the filter's ability to trap particles down to 0.5 microns. These products are perfect for commercial facilities to keep pools clear and clean even during times of peak swimmer load.

Zeolite Upgrade

While plain old sand has been tried and proven as a filter media since ancient times, some pool technicians like the performance of Zeolite as an alternative. Zeolite refers to a group of porous minerals containing silicon, aluminum and oxygen; it is often referred to as a "molecular sieve" for it's fine filtering characteristics.

In the last few years, White has been using Zeolite as a replacement for sand. "If we have the opportunity, one of our newest sand filter renovation techniques involves removing all the old sand and replacing it with Zeolite as a filter media," he says. "We started this practice over the last five years. We find that Zeolite actually filters down to a much smaller particle size and additionally absorbs ammonia.

"Zeolite has nearly 9,800 times more square footage than sand, enabling it to filter small particles down to 3 microns for exceptional water clarity. This filtering media also removes the ammonia produced from dead organic material in the water, reducing eye irritation and odor. Plus, it cuts down on chemical demand. I started using it in my own pool and was immediately sold," he says.

"Changing to Zeolite is a process we generally sell in the winter, at the time of pool closing. We find that this 'end of season' up-selling to Zeolite as we get the pool ready for winter is extremely effective. And by doing so, the pool filter is prepped and ready for the busy spring opening season."

Watch Your Head!

When refilling the sand filter, it's crucial to maintain the proper "head space" above the sand bed. That space is intended to dissipate the turbulence of the incoming flow and produce steady, even water pressure over the sand bed. Without the right amount of head space — which will cause uneven pressure across the sand bed — channeling will result, and water will run straight through the channel without being filtered.

A Little D.E. in the Sand

While D.E. is a filter medium in its own right, savvy service technicians use D.E. in cartridge filters (to help in the cleaning process) and in sand filters as a filtration aid. "We use D.E. as an additive to tighten up the sand and make the sand filter more effective," White says. When cleaning, however, the D.E. will be lost in the backwash and will have to be replaced.

Too Clean!

It's also important not to backwash a sand filter (or any filter) too much. There is a mind-set in some pool owners that when it comes to cleaning that "more is better," and therefore, more frequent backwashing of the filter will keep water clearer. But a minor load of dirt across the top layer in a sand filter actually helps it filter better. As that dirt coats a sand bed, it helps strain out finer material and reduce the cloudiness that results from small micron debris.

Getting Ready For Winter: A Sand Filter Cleaning Tip

Closing season arrives at different times in different regions, and the process of "winterizing" a pool changes as the latitude (and temperature!) drops toward 32 degrees.

In the frozen North, pools are taken offline and their filters made ready for the spring. Cartridge filters are removed for cleaning, while sand beds are prepped so they will be in peak condition for the spring opening.

Soaking the sand bed in a cleaning solution before the final backwash is a great way to avoid some of the problems that can occur in a sand bed after a full season and a long winter.

Dan Lenz, All Seasons Pools & Spas, Orland Park, Ill., uses the following procedure to make ready for next year:

"Before closing sand filters, we use a cleansing solution like ProTeam's Filter Magic or Natural Chemistry's Filter Perfect to do more than just backwashing of the sand. It's a solution that is mixed with five gallons of water, which is poured into the pump and sits overnight before backwashing. We like to do this because we also have the water dropped below the jets before we completely shut down the pool for the winter."

Comments or thoughts on this article? Please e-mail


Scott Webb is Executive Editor of AQUA Magazine.
Outstanding summary of issues even top techs havent learned yet
I keep seeing all this talk on Sand filters and Zeobrite. Ill try and keep this short. Ive been DE all my life until the last 4-5 years. I personally cant stand Sand filters bedded with Sand. 30 Microns is a joke. Especially when you live in Florida. We started installing Pentair Ta-100 D filters bedded with glass. Vitro Clean to be exact. We are achieving 3-5 microns on filtration and haven't had 1 issue to date. It cost about 15.00 per 50 lb bag. It is installed in place of the sand and can be re bedded every 7 years or so. Its as good ( Should I say Better ), than DE. It has the same ease of use as sand without the necessity of having to add DE to your filter. You dont havce to tear it down every year as you do with DE. Although there may be some income lost on the yearly tear down you will lose, it will benefit you through out the year with pristine polished water saving you money on Clarifiers and additional chemicals needed to maintain clarity. If you need clarifiers to maintain clear water, you have the wrong filter.
Here is the formula for bedding the filter with Vitro Clean crushed glass.
Example--Pentair TA100-D. 600 lb sand filter. Take 20% off of the total required sand. 600 - 20 % = 480lb.
Now it a 70/30 split on pea gravel and glass. 70% of 480 =336 lbs of glass. 30 % of 480 =144 lbs of pea gravel to support the laterals. Fill the tank half full of water after leveling. Add your pea gravel 1st. Then your glass. Thats it. Best filter going today. If you have any questions or would like to discuss it any further, you can email me. Enjoy!
Good points David. You might want to top off the filter in year four with an extra bag, maybe two especially if backwashed before the six to ten lb pressure rise Should average three weeks for that rise on a TA100 with VitroClean, 5 to 6 weeks on either AFM or ECOsmarte Glasspack which are both derived from bottle glass and should outperform the best DE on its best day. Also avoid the oversize glass bead bed-- rips the laterals up People are still promoting this and going all glass unfortunately makes sense to the customer. Glasspack uses the data sheets on gravel from Pentair
If you are looking for good performance on larger pools, look to larger filters rather than multiple tanks. It will always be cheaper to line up two or three Tritons. Compare the sand load to the square footage of the tanks. When you use a large steel tank, it will have a lot more sand than a comparable number of Tritons. With a even distribution of laterals, the big tank will also backwash better.
I'll pick a sand filter first every time. Been in the pool business from all angles for over 30 years now too.

Nice article and most pool guys have probably come against these issues and discussed them. My experience has been that filtration rates are an extremely common issue. Great filtration rates will offer very clear water that is pretty much impossible to tell from cartridge or DE as they are often not used properly themselves.

Residentially the filter area is very often too small for the flowrate. Many filters will read 20gpm per sq.ft. but if you ever run a sand filter at 10-12pm per sq.ft. I think you will see a huge improvement in water quality. Its really not much of an upgrade cost and it lends itself to an almost perfect backwash flowrate 15gpm per sq.ft. Also the water doesn't drive the debris so deep into the filter bed. There are a myriad of reasons the pump can be oversized for the job, solar systems, pump replacements where the thinking can be more flow equals cleaner water etc. There is a reason Health Boards want a flowrate of 15gpm per sq.ft. max.

Commercially all the same applies even though the filters are generally much larger and also in multiple configurations. The pumps will often be engineered too large to keep the minimum desired flowrate even as the filter bed loads up. The intent is to have the operator manage the flow over time, possibly with a valve on the pump outlet. I see these left wide open all the time which drives the debris deeper but it also sets the backwash flowrate up to far exceed anything reasonable. This is where you see sand loss and the excessive flow is often the cause of premature lateral failure. Excessive flow will be "cushioned" in filter mode by the sand but in backwash the water just hammers directly into the laterals and can over expand them. There is a huge pressure difference between the inside and outside of the lateral that isn't there while in filter mode.

With the multiple filter configuration there is probably the intent to backwash them all together. They might not backwash evenly resulting in one or more creating more head restriction and the remaining filter gets too much flow. Operators may find it easier and more convenient to just flip one into backwash while the others keep filtering and that is probably not going to end up in any proper backwash flowrate. I, and no doubt many others have seen these and more.

Anyways, I wanted to inject the flow issues as another area of concern with Sand Filtration. It also just came to mind the difficulty is water replacement on Cartridge filtered pools I run across. Much more difficult to beat down excessive CYA and Calcium levels when there is often just nowhere to properly drain a pool for dilution.